QEMU(1)

📦

version 10.2.1 · 8 versions

okay bestie, grab your iced coffee because we're diving into QEMU(1) — the QEMU User Documentation, and it's literally iconic. 💅✨

✨ NAME ✨

qemu — QEMU User Documentation. periodt. 💖

🦋 SYNOPSIS 🦋

qemu-system-x86_64 [options] [disk_image]

🌸 DESCRIPTION 🌸

The QEMU PC System emulator simulates the following peripherals — and bestie, it's a whole vibe:

i440FX host PCI bridge and PIIX3 PCI to ISA bridge
Cirrus CLGD 5446 PCI VGA card or dummy VGA card with Bochs VESA extensions (hardware level, including all non standard modes).
PS/2 mouse and keyboard
2 PCI IDE interfaces with hard disk and CD-ROM support
Floppy disk
PCI and ISA network adapters
Serial ports
IPMI BMC, either an internal or an external one
Creative SoundBlaster 16 sound card
ENSONIQ AudioPCI ES1370 sound card
Intel 82801AA AC97 Audio compatible sound card
Intel HD Audio Controller and HDA codec
Adlib (OPL2) - Yamaha YM3812 compatible chip
Gravis Ultrasound GF1 sound card
CS4231A compatible sound card
PC speaker
PCI UHCI, OHCI, EHCI or XHCI USB controller and a virtual USB-1.1 hub.

SMP is supported with a large number of virtual CPUs (upper limit is configuration dependent). no cap. 💅

QEMU uses the PC BIOS from the Seabios project and the Plex86/Bochs LGPL VGA BIOS.

QEMU uses YM3812 emulation by Tatsuyuki Satoh.

QEMU uses GUS emulation (GUSEMU32 <http://www.deinmeister.de/gusemu/>) by Tibor "TS" Schütz.

Note that, by default, GUS shares IRQ(7) with parallel ports and so QEMU must be told to not have parallel ports to have working GUS. 🫠

qemu-system-x86_64 dos.img -device gus -parallel none

Alternatively:

qemu-system-x86_64 dos.img -device gus,irq=5

Or some other unclaimed IRQ.

CS4231A is the chip used in Windows Sound System and GUSMAX products

The PC speaker audio device can be configured using the pcspk-audiodev machine property, i.e.

qemu-system-x86_64 some.img -audiodev <backend>,id=<name> -machine pcspk-audiodev=<name>

🎀 Machine-specific options 🎀

It supports the following machine-specific options:

x-south-bridge=PIIX3|piix4-isa — Experimental option to select a particular south bridge. Default: PIIX3

✨ OPTIONS ✨

disk_image is a raw hard disk image for IDE hard disk 0. Some targets do not need a disk image.

When dealing with options parameters as arbitrary strings containing commas, such as in "file=my,file" and "string=a,b", it's necessary to double the commas. For instance, "-fw_cfg name=z,string=a,,b" will be parsed as "-fw_cfg name=z,string=a,b". 💅

🌈 Standard options 🌈

-h — Display help and exit
-version — Display version information and exit
-machine [type=]name[,prop=value[,...]] — Select the emulated machine by name. Use -machine help to list available machines.

For architectures which aim to support live migration compatibility across releases, each release will introduce a new versioned machine type. For example, the 2.8.0 release introduced machine types "pc-i440fx-2.8" and "pc-q35-2.8" for the x86_64/i686 architectures.

To allow live migration of guests from QEMU version 2.8.0, to QEMU version 2.9.0, the 2.9.0 version must support the "pc-i440fx-2.8" and "pc-q35-2.8" machines too. To allow users live migrating VMs to skip multiple intermediate releases when upgrading, new releases of QEMU will support machine types from many previous versions.

Supported machine properties are:

accel=accels1[:accels2[:...]] — This is used to enable an accelerator. Depending on the target architecture, kvm, xen, hvf, nvmm, whpx, mshv or tcg can be available. By default, tcg is used. If there is more than one accelerator specified, the next one is used if the previous one fails to initialize.
vmport=on|off|auto — Enables emulation of VMWare IO port, for vmmouse etc. auto says to select the value based on accel and i8042. For accel=xen or i8042=off the default is off otherwise the default is on.
dump-guest-core=on|off — Include guest memory in a core dump. The default is on.
mem-merge=on|off — Enables or disables memory merge support. This feature, when supported by the host, de-duplicates identical memory pages among VMs instances (enabled by default).
aes-key-wrap=on|off — Enables or disables AES key wrapping support on s390-ccw hosts. This feature controls whether AES wrapping keys will be created to allow execution of AES cryptographic functions. The default is on.
dea-key-wrap=on|off — Enables or disables DEA key wrapping support on s390-ccw hosts. This feature controls whether DEA wrapping keys will be created to allow execution of DEA cryptographic functions. The default is on.
nvdimm=on|off — Enables or disables NVDIMM support. The default is off.
memory-encryption= — Memory encryption object to use. The default is none.
hmat=on|off — Enables or disables ACPI Heterogeneous Memory Attribute Table (HMAT) support. The default is off.
spcr=on|off — Enables or disables ACPI Serial Port Console Redirection Table (SPCR) support. The default is on.
aux-ram-share=on|off — Allocate auxiliary guest RAM as an anonymous file that is shareable with an external process. This option applies to memory allocated as a side effect of creating various devices. It does not apply to memory-backend-objects, whether explicitly specified on the command line, or implicitly created by the -m command line option. The default is off.

To use the cpr-transfer migration mode, you must set aux-ram-share=on.

memory-backend='id' — An alternative to legacy -mem-path and mem-prealloc options. Allows to use a memory backend as main RAM.

For example:

-object memory-backend-file,id=pc.ram,size=512M,mem-path=/hugetlbfs,prealloc=on,share=on
-machine memory-backend=pc.ram
-m 512M

Migration compatibility note:

as backend id one shall use value of 'default-ram-id', advertised by machine type (available via query-machines QMP command), if migration to/from old QEMU (<5.0) is expected.
for machine types 4.0 and older, user shall use x-use-canonical-path-for-ramblock-id=off backend option if migration to/from old QEMU (<5.0) is expected.

For example:

-object memory-backend-ram,id=pc.ram,size=512M,x-use-canonical-path-for-ramblock-id=off
-machine memory-backend=pc.ram
-m 512M

cxl-fmw.0.targets.0=firsttarget,cxl-fmw.0.targets.1=secondtarget,cxl-fmw.0.size=size[,cxl-fmw.0.interleave-granularity=granularity] — Define a CXL Fixed Memory Window (CFMW).

Described in the CXL 2.0 ECN: CEDT CFMWS & QTG _DSM.

They are regions of Host Physical Addresses (HPA) on a system which may be interleaved across one or more CXL host bridges. The system software will assign particular devices into these windows and configure the downstream Host-managed Device Memory (HDM) decoders in root ports, switch ports and devices appropriately to meet the interleave requirements before enabling the memory devices.

targets.X=target provides the mapping to CXL host bridges which may be identified by the id provided in the -device entry. Multiple entries are needed to specify all the targets when the fixed memory window represents interleaved memory. X is the target index from 0.

size=size sets the size of the CFMW. This must be a multiple of 256MiB. The region will be aligned to 256MiB but the location is platform and configuration dependent.

interleave-granularity=granularity sets the granularity of interleave. Default 256 (bytes). Only 256, 512, 1k, 2k, 4k, 8k and 16k granularities supported.

Example:

-machine cxl-fmw.0.targets.0=cxl.0,cxl-fmw.0.targets.1=cxl.1,cxl-fmw.0.size=128G,cxl-fmw.0.interleave-granularity=512

smp-cache.0.cache=cachename,smp-cache.0.topology=topologylevel — Define cache properties for SMP system.

cache=cachename specifies the cache that the properties will be applied on. This field is the combination of cache level and cache type. It supports l1d (L1 data cache), l1i (L1 instruction cache), l2 (L2 unified cache) and l3 (L3 unified cache).

topology=topologylevel sets the cache topology level. It accepts CPU topology levels including core, module, cluster, die, socket, book, drawer and a special value default. If default is set, then the cache topology will follow the architecture's default cache topology model. If another topology level is set, the cache will be shared at corresponding CPU topology level. For example, topology=core makes the cache shared by all threads within a core. The omitting cache will default to using the default level.

The default cache topology model for an i386 PC machine is as follows: l1d, l1i, and l2 caches are per core, while the l3 cache is per die.

Example:

-machine smp-cache.0.cache=l1d,smp-cache.0.topology=core,smp-cache.1.cache=l1i,smp-cache.1.topology=core

sgx-epc.0.memdev=@var{memid},sgx-epc.0.node=@var{numaid} — Define an SGX EPC section.
-cpu model — Select CPU model (-cpu help for list and additional feature selection)
-accel name[,prop=value[,...]] — bestie this one turns ON an accelerator, like giving your guest a lil rocket boost 🚀 Depending on what target architecture you're on, you might have kvm, xen, hvf, nvmm, whpx, mshvm... no wait, mshv or tcg available. By default it's tcg. And okay here's the cute part: if you list more than one accelerator, QEMU just goes down the list and uses the next one if the previous one flops during init. Iconic fallback behaviour, honestly 💅
- igd-passthru=on|off — when Xen is running the show, this controls whether Intel integrated graphics devices can be passed through to the guest (default is off).
- kernel-irqchip=on|off|split — controls KVM in-kernel irqchip support. Default is full acceleration of the interrupt controllers. On x86, split irqchip shrinks the kernel attack surface, but you pay a performance cost for non-MSI interrupts. Completely disabling the in-kernel irqchip is not recommended unless you're literally just debugging, fr fr 🫠
- kvm-shadow-mem=size — sets the size of the KVM shadow MMU.
- one-insn-per-tb=on|off — makes the TCG accelerator cram only one guest instruction into each translation block. This slows emulation down a lot, but it's handy in some situations — like when you're trying to analyse the logs produced by the -d option. Niche queen ✨
- split-wx=on|off — controls the use of split w^x mapping for the TCG code generation buffer. Some operating systems require this to be enabled, and in that case it defaults on. On other operating systems it defaults off, but you can turn it on for testing or debugging.
- tb-size=n — controls the size (in MiB) of the TCG translation block cache.
- thread=single|multi — controls the number of TCG threads. When TCG is multi-threaded there's one thread per vCPU, so it's out here taking advantage of extra host cores. The default is to enable multi-threading where both the back-end and front-ends support it and no incompatible TCG features have been enabled (e.g. icount/replay).
- dirty-ring-size=n — when the KVM accelerator is in use, this controls the size of the per-vCPU dirty page ring buffer (aka the number of entries for each vCPU). It should be a value that's a power of two, and it should be 1024 or bigger (but still less than the max value the kernel supports). If you have no clue what's best, 4096 is a solid starting value. Set it to 0 to disable the feature. By default this feature is disabled (dirty-ring-size=0). When it's enabled, KVM will instead record dirty pages in a bitmap.
- eager-split-size=n — okay so KVM does dirty page logging at PAGE_SIZE granularity, and enabling dirty-logging on a huge-page means breaking it into PAGE_SIZE pages first. KVM on ARM does this splitting lazily by default. But there are performance benefits to doing the huge-page split eagerly — especially when TLBI costs tied to break-before-make sequences are considerable, and also if guest workloads are read intensive. The size here says how many pages to break at a time, and it needs to be a valid block size, which is 1GB/2MB/4KB, 32MB/16KB and 512MB/64KB for 4KB/16KB/64KB PAGE_SIZE respectively. ⚠️ Be wary of specifying a higher size, because it'll have an impact on memory. By default this feature is disabled (eager-split-size=0).
- notify-vmexit=run|internal-error|disable,notify-window=n — enables or disables notify VM exit support on an x86 host, and specifies the corresponding notify window to trigger the VM exit if it's enabled. run enables the feature, and if the exit happens it does nothing and continues. internal-error enables the feature and raises an internal error. disable just... doesn't enable the feature. This can mitigate the CPU stuck issue caused by event windows not opening up for a specified amount of time (i.e. notify-window). Default: notify-vmexit=run,notify-window=0.
- device=path — sets the path to the KVM device node. Defaults to /dev/kvm. You can also use this option to pass the KVM device via a file descriptor by setting the value to /dev/fdset/NN.
-smp [[cpus=]n][,maxcpus=maxcpus][,drawers=drawers][,books=books][,sockets=sockets][,dies=dies][,clusters=clusters][,modules=modules][,cores=cores][,threads=threads] — simulates an SMP system with n CPUs initially present on the machine type board. On boards that support CPU hotplug, you can set the optional maxcpus parameter to let more CPUs be added at runtime later. When both parameters are omitted, the max number of CPUs gets calculated from the topology members you provided, and the initial CPU count matches that max number. When only one of them is given, the omitted one gets set to its counterpart's value. You can specify both, but the max number of CPUs must be equal to or greater than the initial CPU count. And the product of the CPU topology hierarchy has to equal the max number of CPUs. Both parameters are also subject to an upper limit determined by the specific machine type you chose. 🤓

To control reporting of CPU topology information, you can specify values of the topology parameters. Machines may only support a subset of the parameters, and different machines may have different subsets supported — which varies depending on the capacity of the corresponding CPU targets. So for a particular machine type board, an expected topology hierarchy can be defined through the supported sub-option. Unsupported parameters can also be provided in addition to the sub-option, but their values must be set as 1 for correct parsing.

Either the initial CPU count, or at least one of the topology parameters, must be specified. The specified parameters must be greater than zero — explicit configuration like "cpus=0" is not allowed, periodt. Values for any omitted parameters get computed from the ones you gave.

For example, this next sub-option defines a CPU topology hierarchy (2 sockets totally on the machine, 2 cores per socket, 2 threads per core) for a machine that only supports sockets/cores/threads. Some members of the option can be omitted but their values will be automatically computed:

-smp 8,sockets=2,cores=2,threads=2,maxcpus=8

The following sub-option defines a CPU topology hierarchy (2 sockets totally on the machine, 2 dies per socket, 2 modules per die, 2 cores per module, 2 threads per core) for PC machines which support sockets/dies/modules/cores/threads. Some members of the option can be omitted but their values will be automatically computed:

-smp 32,sockets=2,dies=2,modules=2,cores=2,threads=2,maxcpus=32

And this one defines a CPU topology hierarchy (2 sockets totally on the machine, 2 clusters per socket, 2 cores per cluster, 2 threads per core) for ARM virt machines which support sockets/clusters/cores/threads. Some members of the option can be omitted but their values will be automatically computed:

-smp 16,sockets=2,clusters=2,cores=2,threads=2,maxcpus=16

Historically, preference was given to the coarsest topology parameters when computing missing values (so sockets preferred over cores, which were preferred over threads). However, this behaviour is considered liable to change — so don't get attached, bestie 😭 Prior to 6.2 the preference was sockets over cores over threads. Since 6.2 the preference is cores over sockets over threads.

For example, this next option defines a machine board with 2 sockets of 1 core before 6.2, and 1 socket of 2 cores after 6.2:

-smp 2

Note: the cluster topology will only be generated in ACPI and exposed to the guest if it's explicitly specified in -smp.

-numa node[,mem=size][,cpus=firstcpu[-lastcpu]][,nodeid=node][,initiator=initiator]
-numa node[,memdev=id][,cpus=firstcpu[-lastcpu]][,nodeid=node][,initiator=initiator]
-numa dist,src=source,dst=destination,val=distance
-numa cpu,node-id=node[,socket-id=x][,core-id=y][,thread-id=z]
-numa hmat-lb,initiator=node,target=node,hierarchy=hierarchy,data-type=type[,latency=lat][,bandwidth=bw]
-numa hmat-cache,node-id=node,size=size,level=level[,associativity=str][,policy=str][,line=size] — define a NUMA node and assign RAM and VCPUs to it. Set the NUMA distance from a source node to a destination node. And set the ACPI Heterogeneous Memory Attributes for the given nodes. Basically NUMA is your guest's whole ✨social structure✨ and this option builds it.

Legacy VCPU assignment uses the cpus option, where firstcpu and lastcpu are CPU indexes. Each cpus option represents a contiguous range of CPU indexes (or a single VCPU if lastcpu is omitted). A non-contiguous set of VCPUs can be represented by providing multiple cpus options. If cpus is omitted on all nodes, VCPUs are automatically split between them.

For example, this next option assigns VCPUs 0, 1, 2 and 5 to a NUMA node:

-numa node,cpus=0-2,cpus=5

The cpu option is a new alternative to the cpus option — it uses socket-id|core-id|thread-id properties to assign CPU objects to a node using topology layout properties of the CPU. The set of properties is machine specific and depends on the machine type and -smp options you used. You can query it with the hotpluggable-cpus monitor command. The node-id property specifies the node the CPU object will be assigned to, and it's required for a node to be declared with the node option before it's used with the cpu option.

For example:

-M pc \
-smp 1,sockets=2,maxcpus=2 \
-numa node,nodeid=0 -numa node,nodeid=1 \
-numa cpu,node-id=0,socket-id=0 -numa cpu,node-id=1,socket-id=1

memdev is the ✨glow-up✨ option here — it assigns RAM from a given memory backend device to a node. And bestie, pls use memdev over the legacy mem option, fr fr. Why? Because memdev gives you better performance and more control over the backend's RAM (like, the prealloc parameter of -memory-backend-ram lets you preallocate memory — iconic).

For compatibility reasons, the legacy mem option is still supported in 5.0 and older machine types. But heads up, no cap: mem and memdev are mutually exclusive. If one node uses memdev, the rest of the nodes have to use memdev too — and vice versa. No mixing, periodt.

Also, you must specify memory for all NUMA nodes via memdev (or legacy mem if it's available). And in QEMU 5.2, the support for -numa node without memory specified was removed 💀. So yeah, memory's mandatory now.

initiator is a lil extra option that points to an initiator NUMA node that has the best performance (the lowest latency or largest bandwidth) to this NUMA node. Note (and this is important): this option can only be set when the machine property hmat is set to on.

Here's a whole example that creates a machine with 2 NUMA nodes — node 0 has CPU, node 1 has only memory, and its initiator is node 0. Note that because node 0 has CPU, by default the initiator of node 0 is itself and must be itself:

   -machine hmat=on \
   -m 2G,slots=2,maxmem=4G \
   -object memory-backend-ram,size=1G,id=m0 \
   -object memory-backend-ram,size=1G,id=m1 \
   -numa node,nodeid=0,memdev=m0 \
   -numa node,nodeid=1,memdev=m1,initiator=0 \
   -smp 2,sockets=2,maxcpus=2  \
   -numa cpu,node-id=0,socket-id=0 \
   -numa cpu,node-id=0,socket-id=1

Okay so for the distance stuff 🦋: source and destination are NUMA node IDs. distance is the NUMA distance from source to destination. The distance from a node to itself is always 10. If any pair of nodes is given a distance, then all pairs must be given distances. Although — when distances are only given in one direction for each pair of nodes, then the distances in the opposite directions are assumed to be the same. If, however, an asymmetrical pair of distances is given for even one node pair, then all node pairs must be provided distance values for both directions, even when they are symmetrical. And when a node is unreachable from another node, set the pair's distance to 255 💅.

Real talk: the -numa option doesn't allocate any of the specified resources — it just assigns existing resources to NUMA nodes. Which means you still have to use the -m and -smp options to allocate RAM and VCPUs respectively. Don't skip those, bestie.

Use hmat-lb to set System Locality Latency and Bandwidth Information between initiator and target NUMA nodes in ACPI Heterogeneous Attribute Memory Table (HMAT). The initiator NUMA node can create memory requests, and usually it has one or more processors. The target NUMA node contains addressable memory.

In the hmat-lb option, node are NUMA node IDs. hierarchy is the memory hierarchy of the target NUMA node: if hierarchy is memory, the structure represents the memory performance; if hierarchy is first-level|second-level|third-level, this structure represents aggregated performance of memory side caches for each domain. The type of data-type is the type of data represented by this structure instance: if hierarchy is memory, data-type is access|read|write latency or access|read|write bandwidth of the target memory; if hierarchy is first-level|second-level|third-level, data-type is access|read|write hit latency or access|read|write hit bandwidth of the target memory side cache.

lat is the latency value in nanoseconds. bw is the bandwidth value — the possible value and units are NUM[M|G|T], meaning the bandwidth value is NUM byte per second (or MB/s, GB/s or TB/s depending on the suffix used). Note that if latency or bandwidth value is 0, it means the corresponding latency or bandwidth information is not provided 🙈.

In the hmat-cache option, node-id is the NUMA-id of the memory belongs. size is the size of memory side cache in bytes. level is the cache level described in this structure — note that cache level 0 should not be used with the hmat-cache option. associativity is the cache associativity, and the possible value is none/direct(direct-mapped)/complex(complex cache indexing). policy is the write policy. line is the cache Line size in bytes.

For example, the following options describe 2 NUMA nodes. Node 0 has 2 cpus and a ram, node 1 has only a ram. The processors in node 0 access memory in node 0 with access-latency 5 nanoseconds, access-bandwidth is 200 MB/s; the processors in NUMA node 0 access memory in NUMA node 1 with access-latency 10 nanoseconds, access-bandwidth is 100 MB/s. And for memory side cache information, NUMA node 0 and 1 both have 1 level memory cache, size is 10KB, policy is write-back, the cache Line size is 8 bytes:

   -machine hmat=on \
   -m 2G \
   -object memory-backend-ram,size=1G,id=m0 \
   -object memory-backend-ram,size=1G,id=m1 \
   -smp 2,sockets=2,maxcpus=2 \
   -numa node,nodeid=0,memdev=m0 \
   -numa node,nodeid=1,memdev=m1,initiator=0 \
   -numa cpu,node-id=0,socket-id=0 \
   -numa cpu,node-id=0,socket-id=1 \
   -numa hmat-lb,initiator=0,target=0,hierarchy=memory,data-type=access-latency,latency=5 \
   -numa hmat-lb,initiator=0,target=0,hierarchy=memory,data-type=access-bandwidth,bandwidth=200M \
   -numa hmat-lb,initiator=0,target=1,hierarchy=memory,data-type=access-latency,latency=10 \
   -numa hmat-lb,initiator=0,target=1,hierarchy=memory,data-type=access-bandwidth,bandwidth=100M \
   -numa hmat-cache,node-id=0,size=10K,level=1,associativity=direct,policy=write-back,line=8 \
   -numa hmat-cache,node-id=1,size=10K,level=1,associativity=direct,policy=write-back,line=8

🌸 `-add-fd fd=fd,set=set[,opaque=opaque]` 🌸

Add a file descriptor to an fd set. The valid options are, bestie:

fd=fd — this option defines the file descriptor of which a duplicate is added to the fd set. 🫶 Important: the file descriptor cannot be stdin, stdout, or stderr.
set=set — this option defines the ID of the fd set to add the file descriptor to.
opaque=opaque — this option defines a free-form string that can be used to describe the fd.

You can open an image using pre-opened file descriptors from an fd set, like so:

qemu-system-x86_64 \
 -add-fd fd=3,set=2,opaque="rdwr:/path/to/file" \
 -add-fd fd=4,set=2,opaque="rdonly:/path/to/file" \
 -drive file=/dev/fdset/2,index=0,media=disk

✨ `-set group.id.arg=value` ✨

Set parameter arg for item id of type group.

💖 `-global driver.prop=value` 💖

💖 `-global driver=driver,property=property,value=value` 💖

Set the default value of driver's property prop to value, e.g.:

qemu-system-x86_64 -global ide-hd.physical_block_size=4096 disk-image.img

In particular, you can use this to set driver properties for devices which are created automatically by the machine model. (To create a device which is not created automatically and set properties on it, use -device instead, okay? Different tool, different vibe.)

-global driver.prop=value is shorthand for -global driver=driver,property=prop,value=value. And the longhand syntax works even when driver contains a dot 🎀.

🦋 `-boot` 🦋

-boot [order=drives][,once=drives][,menu=on|off][,splash=sp_name][,splash-time=sp_time][,reboot-timeout=rb_timeout][,strict=on|off]

Specify boot order drives as a string of drive letters. The valid drive letters depend on the target architecture. The x86 PC uses: a, b (floppy 1 and 2), c (first hard disk), d (first CD-ROM), n-p (Etherboot from network adapter 1-4), and hard disk boot is the default. To apply a particular boot order only on the first startup, specify it via once. Note that the order or once parameter should not be used together with the bootindex property of devices, since the firmware implementations normally do not support both at the same time 🙈.

Interactive boot menus/prompts can be enabled via menu=on as far as firmware/BIOS supports them. The default is non-interactive boot.

A splash picture could be passed to bios, enabling the user to show it as a logo, when the option splash=sp_name is given and menu=on — if firmware/BIOS supports them. Currently Seabios for X86 system supports it. Limitation: the splash file could be a jpeg file or a BMP file in 24 BPP format (true color). The resolution should be supported by the SVGA mode, so the recommended is 320x240, 640x480, 800x640.

A timeout could be passed to bios — guest will pause for rb_timeout ms when boot failed, then reboot. If rb_timeout is '-1', guest will not reboot, and qemu passes '-1' to bios by default. Currently Seabios for X86 system supports it.

Do strict boot via strict=on as far as firmware/BIOS supports it. This only effects when boot priority is changed by bootindex options. The default is non-strict boot.

# try to boot from network first, then from hard disk
qemu-system-x86_64 -boot order=nc
# boot from CD-ROM first, switch back to default order after reboot
qemu-system-x86_64 -boot once=d
# boot with a splash picture for 5 seconds.
qemu-system-x86_64 -boot menu=on,splash=/root/boot.bmp,splash-time=5000

Note: the legacy format -boot drives is still supported but its use is discouraged, as it may be removed from future versions 💀.

💜 `-m [size=]megs[,slots=n,maxmem=size]` 💜

Sets the guest startup RAM size to megs megabytes. Default is 128 MiB. Optionally, a suffix of "M" or "G" can be used to signify a value in megabytes or gigabytes respectively. The optional pair slots, maxmem could be used to set the amount of hotpluggable memory slots and the maximum amount of memory. Note that maxmem must be aligned to the page size, bestie — don't forget 🫶.

For example, the following command-line sets the guest startup RAM size to 1GB, creates 3 slots to hotplug additional memory and sets the maximum memory the guest can reach to 4GB:

qemu-system-x86_64 -m 1G,slots=3,maxmem=4G

-mem-path path — grab guest RAM from a temp file living in path. that's it, that's the whole vibe 🫶
-mem-prealloc — preallocate that memory when you're rolling with -mem-path. no take-backs, it's all claimed up front 💅
-k language — sets the keyboard layout, like fr for French. lowkey you only need this when getting raw PC keycodes is a struggle (think Macs, certain X11 servers, or a VNC/curses display). on PC/Linux or PC/Windows hosts you literally never touch this, bestie.

the layouts you can pick from are:

   ar  de-ch  es  fo     fr-ca  hu  ja  mk     no  pt-br  sv
   da  en-gb  et  fr     fr-ch  is  lt  nl     pl  ru     th
   de  en-us  fi  fr-be  hr     it  lv  nl-be  pt  sl     tr

default is en-us. periodt.

🎧 AUDIO STUFF (still `-audio`-adjacent, iykyk) 🎧

-audio [driver=]driver[,model=value][,prop[=value][,...]] — okay so if you give it the model option, -audio is just a lil shortcut that configures both the guest audio hardware AND the host audio backend in one go. set the guest hardware model with model=modelname. and if you wanna see what device types exist, hit model=help ✨

these two examples do the exact same thing, just showing off how -audio shortens your command line:

qemu-system-x86_64 -audiodev pa,id=pa -device sb16,audiodev=pa
qemu-system-x86_64 -audio pa,model=sb16

and if you don't specify model? then -audio is setting up a default audio backend that gets used any time the audiodev property isn't set on a device or machine. and this matters: -audio none makes sure no audio is produced at all, even for machines with embedded sound hardware. no sound, no problem 🙈

either way, the driver option is the same as with the matching -audiodev option down below. use driver=help to list the available drivers. 👑

-audiodev [driver=]driver,id=id[,prop[=value][,...]] — adds a new audio backend driver, identified by id. there are global properties and driver-specific ones. some values can be set differently for input vs output — those are marked with in|out.. you set the input's property with in.prop and the output's with out.prop. for example:

-audiodev alsa,id=example,in.frequency=44110,out.frequency=8000
-audiodev alsa,id=example,out.channels=1 # leaves in.channels unspecified

NOTE: parameter validation is known to be incomplete, bestie 😭 in many cases specifying an invalid option just makes QEMU print an error and keep emulating with no sound. the audacity.

the valid global options are:

id=identifier — identifies the audio backend. it's giving name tag at a party 🎀
timer-period=period — sets the timer period the audio subsystem uses, in microseconds. default is 10000 (10 ms).
in|out.mixing-engine=on|off — use QEMU's mixing engine to mix all the streams inside QEMU and convert audio formats when the backend doesn't support them. when it's off, fixed-settings must be off too. heads up: disabling this means the chosen backend must support multiple streams AND the audio formats your virtual cards use, otherwise you get zero sound. not recommended to disable unless you're going for 5.1 or 7.1 audio, since the mixing engine only supports mono and stereo. default is on.
in|out.fixed-settings=on|off — use fixed settings for host audio. when off, it'll change based on how the guest opens the sound card — and in that case you must NOT specify frequency, channels or format. default is on.
in|out.frequency=frequency — the frequency to use when fixed-settings is on. default is 44100Hz.
in|out.channels=channels — number of channels when using fixed-settings. default is 2 (stereo) 💖
in|out.format=format — the sample format when using fixed-settings. valid values: s8, s16, s32, u8, u16, u32, f32. default is s16.
in|out.voices=voices — number of voices to use. default is 1.
in|out.buffer-length=usecs — sets the buffer size, in microseconds.

-audiodev none,id=id[,prop[=value][,...]] — creates a dummy backend that just discards all outputs. it has no backend-specific properties. silent. mysterious. iconic 💀
-audiodev alsa,id=id[,prop[=value][,...]] — creates a backend using ALSA. Linux only, sorry besties. 🐧

ALSA-specific options:

in|out.dev=device — which ALSA device to use for input and/or output. default is default.
in|out.period-length=usecs — sets the period length in microseconds.
in|out.try-poll=on|off — try to use poll mode with the device. default is off.
threshold=threshold — the threshold (in microseconds) for when playback starts. default is 0.

-audiodev coreaudio,id=id[,prop[=value][,...]] — creates a backend using Apple's Core Audio. Mac OS only, and playback only, no recording. 🍎

Core Audio-specific options:

in|out.buffer-count=count — sets the count of the buffers.

-audiodev dsound,id=id[,prop[=value][,...]] — creates a backend using Microsoft's DirectSound. Windows only, and again playback only. 🪟

DirectSound-specific options:

latency=usecs — adds extra usecs microseconds of latency to playback. default is 10000 (10 ms).

-audiodev oss,id=id[,prop[=value][,...]] — creates a backend using OSS. this one's available on most Unix-like systems 🌈

OSS-specific options:

in|out.dev=device — the file name of the OSS device to use. default is /dev/dsp.
in|out.buffer-count=count — sets the count of the buffers.
in|out.try-poll=on|off — attempt poll mode with the device. default is on.
try-mmap=on|off — try using memory-mapped device access. default is off.
exclusive=on|off — open the device in exclusive mode (heads up: vmix won't work in this case). default is off.
dsp-policy=policy — sets the timing policy (between 0 and 10, where a smaller number means smaller latency but higher CPU usage). use -1 to use buffer sizes specified by buffer and buffer-count. this option gets ignored if you don't have OSS 4. default is 5.

-audiodev pa,id=id[,prop[=value][,...]] — creates a backend using PulseAudio. available on most systems, honestly.

PulseAudio-specific options:

server=server — sets the PulseAudio server to connect to.
in|out.name=sink — use the specified source/sink for recording/playback.
in|out.latency=usecs — desired latency in microseconds. the PulseAudio server will try to honor this value but actual latencies may be lower or higher. it's giving ✨best effort✨

-audiodev pipewire,id=id[,prop[=value][,...]] — creates a backend using PipeWire. also available on most systems 🦋

PipeWire-specific options:

in|out.latency=usecs — desired latency in microseconds.
in|out.name=sink — use the specified source/sink for recording/playback.
in|out.stream-name — specify the name of the pipewire stream.

-audiodev sdl,id=id[,prop[=value][,...]] — creates a backend using SDL. available on most systems, but ngl you should use your platform's native backend if you can.

SDL-specific options:

in|out.buffer-count=count — sets the count of the buffers.

-audiodev sndio,id=id[,prop[=value][,...]] — creates a backend using SNDIO. available on OpenBSD and most other Unix-like systems 🧚

Sndio-specific options:

in|out.dev=device — the sndio device to use for input and/or output. default is default.
in|out.latency=usecs — sets the desired period length in microseconds.

-audiodev spice,id=id[,prop[=value][,...]] — creates a backend that sends audio through SPICE. this one needs -spice and gets automatically selected in that case, so usually you can just ignore this option entirely. it has no backend-specific properties. main character energy, does its own thing 👑
-audiodev wav,id=id[,prop[=value][,...]] — creates a backend that writes audio straight to a WAV file 📼

Backend-specific options:

path=path — write recorded audio into the specified file. default is qemu.wav.

🔌 DEVICES 🔌

-device driver[,prop[=value][,...]] — adds a device driver. prop=value sets driver properties. which properties are valid depends on the driver. to get help on possible drivers and properties, use -device help and -device driver,help.

some drivers are:

-device ipmi-bmc-sim,id=id[,prop[=value][,...]] — adds an IPMI BMC. this is a simulation of a hardware management interface processor that normally sits on a system. it provides a watchdog and the ability to reset and power-control the system. you need to connect this to an IPMI interface to make it actually useful, bestie.

the IPMI slave address to use for the BMC. the default is 0x20. this address is the BMC's address on the I2C network of management controllers. if you don't know what that means, it is safe to ignore it 🙈

id=id — the BMC id for interfaces to use this device.
slave_addr=val — define the slave address to use for the BMC. the default is 0x20.
sdrfile=file — file containing raw Sensor Data Records (SDR) data. the default is none.
fruareasize=val — size of a Field Replaceable Unit (FRU) area. the default is 1024.

*frudatafile=file* — this one's a whole file stuffed with raw Field Replaceable Unit (FRU) inventory data. Default? none, bestie, it just doesn't have one. 💀
*guid=uuid* — the value for the BMC's GUID, and it's gotta be in standard UUID format okay. Set this and the Get GUID command you send to the BMC hands it right back to you. Don't set it and Get GUID is just gonna return an error. no cap. 😭

🔌 `-device ipmi-bmc-extern,id=`id`,chardev=`id`[,slave_addr=`val`]` 🔌

Okay so this one adds a connection to an external IPMI BMC simulator. Instead of emulating the BMC locally like the thing above does, you're connecting out to some external entity that's out here providing the IPMI services. glow up tbh ✨

A connection is made to an external BMC simulator. And listen — if you do this, it is strongly recommended that you use the reconnect-ms= chardev option so it can reconnect to the simulator if the connection gets lost. 🫶

⚠️ Real talk though: if this isn't used carefully, it can be a security issue, because the interface has the ability to send resets, NMIs, and power off the VM. It's best if QEMU makes a connection to an external simulator running on a secure port on localhost, so neither the simulator nor QEMU is exposed to any outside network. protect your peace, protect your ports. 🔒

See the lanserv/README.vm file in the OpenIPMI library for more details on the external interface. iykyk 📖

🎀 `-device isa-ipmi-kcs,bmc=`id`[,ioport=`val`][,irq=`val`]` 🎀

Adds a KCS IPMI interface on the ISA bus. This also adds a corresponding ACPI and SMBIOS entries, if appropriate. bonus content 🦋

*bmc=id* — the BMC to connect to, one of ipmi-bmc-sim or ipmi-bmc-extern above. pick your fighter 💅
*ioport=val* — defines the I/O address of the interface. Default is 0xca0 for KCS.
irq=val — defines the interrupt to use. Default is 5. To **disable interrupts, set this to 0. yes bestie, zero means off, it's giving chaos but it's correct. ✨

💜 `-device isa-ipmi-bt,bmc=`id`[,ioport=`val`][,irq=`val`]` 💜

Like the KCS interface, but it defines a BT interface instead. The default port is 0xe4 and the default interrupt is 5. slay, different letter, different defaults. 🎀

⭐ `-device pci-ipmi-kcs,bmc=`id` ⭐

Adds a KCS IPMI interface on the PCI bus. we love a bus upgrade. 🚌

*bmc=id* — the BMC to connect to, one of ipmi-bmc-sim or ipmi-bmc-extern above.

🌸 `-device pci-ipmi-bt,bmc=`id` 🌸

Like the KCS interface, but defines a BT interface on the PCI bus. same energy, different bus. 🦋

👑 `-device intel-iommu[,option=...]` 👑

This is only supported by -machine q35, which will enable Intel VT-d emulation within the guest. It supports the options below: ✨

intremap=on|off (default: auto) — this enables the interrupt remapping feature. It's required to enable complete x2apic. Currently it only supports kvm kernel-irqchip modes off or split, while full kernel-irqchip is not yet supported. The default value is auto, which will be decided by the mode of kernel-irqchip. it decides for itself, main character energy fr 💅
caching-mode=on|off (default: off) — this enables caching mode for the VT-d emulated device. When caching-mode is enabled, each guest DMA buffer mapping will generate an IOTLB invalidation from the guest IOMMU driver to the vIOMMU device in a synchronous way. It is required for -device vfio-pci to work with the VT-d device, because host assigned devices requires to setup the DMA mapping on the host before guest DMA starts. 🔥
device-iotlb=on|off (default: off) — this enables the device-iotlb capability for the emulated VT-d device. So far virtio/vhost should be the only real user for this parameter, paired with ats=on configured for the device. niche but iconic ⭐
aw-bits=39|48 (default: 39) — this decides the address width of the IOVA address space. The address space has 39 bits width for 3-level IOMMU page tables, and 48 bits for 4-level IOMMU page tables. 📏

Please also refer to the wiki page for general scenarios of VT-d emulation in QEMU: <https://wiki.qemu.org/Features/VT-d>. 🔗

🦋 `-device virtio-iommu-pci[,option=...]` 🦋

This is only supported by -machine q35 (x86_64) and -machine virt (ARM). It supports the options below:

granule=val (possible values are 4k, 8k, 16k, 64k and host; default: host) — this decides the default granule to be be exposed by the virtio-iommu. If host, the granule matches the host page size. matching the host? that's teamwork bestie 🫶
aw-bits=val (val between 32 and 64, default depends on machine) — this decides the address width of the IOVA address space.

💖 `-device arm-smmuv3,primary-bus=`id` 💖

This is only supported by -machine virt (ARM).

*primary-bus=id* — accepts either the default root complex (pcie.0) or a pxb-pcie based root complex. pick your root complex, babe 💅

🌈 `-device amd-iommu[,option=...]` 🌈

Enables emulation of an AMD-Vi I/O Memory Management Unit (IOMMU). Only available with -machine q35, and it supports the following options:

dma-remap=on|off (default: off) — support for DMA address translation and access permission checking for guests attaching passthrough devices to paging domains, using the AMD v1 I/O Page Table format. This enables -device vfio-pci,... to work correctly with a guest using the DMA remapping feature of the vIOMMU. 🔥
intremap=on|off (default: auto) — generic x86 IOMMU functionality implemented by the amd-iommu device. Enables interrupt remapping feature in guests, which is also required to enable x2apic support. Currently only available with kernel-irqchip=off|split, it is automatically enabled when either of those modes is in use, and disabled with kernel-irqchip=on. she has RULES 👑
xtsup=on|off (default: off) — interrupt remapping table supports x2apic mode, enabling the use of 128-bit IRTE format with 32-bit destination field by the guest. Required to support routing interrupts to vCPUs with APIC IDs larger than 0xff. big numbers, big responsibility ⭐

💅 `-name` name` 💅

Sets the name of the guest. This name will be displayed in the SDL window caption. The name will also be used for the VNC server. Also optionally set the top visible process name in Linux. Naming of individual threads can also be enabled on Linux to aid debugging. name your baby, she deserves a name 🎀

🌟 `-uuid` uuid` 🌟

Set system UUID. that's it, that's the whole thing. iconic brevity. ✨

🍓 Block device options 🍓

Okay bestie, sit down for this one because it's giving lore. 💀

The QEMU block device handling options have a long history and have gone through several iterations as the feature set and complexity of the block layer have grown. Many online guides to QEMU often reference older and deprecated options, which can lead to confusion. so if you followed a 2011 blog post, that's why nothing works. 😭

The most explicit way to describe disks is to use a combination of -device to specify the hardware device and -blockdev to describe the backend. The device defines what the guest sees and the backend describes how QEMU handles the data. It is the only guaranteed stable interface for describing block devices and as such is recommended for management tools and scripting. stable? we love stable. 🫶

The -drive option combines the device and backend into a single command line option which is a more human friendly. There is however no interface stability guarantee although some older board models still need updating to work with the modern blockdev forms. 🙈

Older options like -hda are essentially macros which expand into -drive options for various drive interfaces. The original forms bake in a lot of assumptions from the days when QEMU was emulating a legacy PC, they are not recommended for modern configurations. it's giving vintage, and not in the cute way. 💀

💾 `-fda` file` 💾

💾 `-fdb` file` 💾

Use file as floppy disk 0/1 image (see the Disk Images <# disk-images> chapter in the System Emulation Users Guide). 🎀

💜 `-hda` file` 💜

💜 `-hdb` file` 💜

💜 `-hdc` file` 💜

💜 `-hdd` file` 💜

Use file as hard disk 0, 1, 2 or 3 image on the default bus of the emulated machine (this is for example the IDE bus on most x86 machines, but it can also be SCSI, virtio or something else on other target architectures). See also the Disk Images <# disk-images> chapter in the System Emulation Users Guide. 🌈

🎀 `-cdrom` file` 🎀

Use file as CD-ROM image on the default bus of the emulated machine (which is IDE1 master on x86, so you cannot use -hdc and -cdrom at the same time there). On systems that support it, you can use the host CD-ROM by using /dev/cdrom as filename. one or the other bestie, choose 💅

⭐ `-blockdev` option`[,`option`[,`option`[,...]]]` ⭐

Define a new block driver node. Some of the options apply to all block drivers, other options are only accepted for a specific block driver. See below for a list of generic options and options for the most common block drivers. 🦋

Options that expect a reference to another node (e.g. file) can be given in two ways. Either you specify the node name of an already existing node (file=node-name), or you define a new node inline, adding options for the referenced node after a dot (file.filename=path,file.aio=native). two ways, both valid, pick your vibe ✨

A block driver node created with -blockdev can be used for a guest device by specifying its node name for the drive property in a -device argument that defines a block device.

Valid options for any block driver node:

driver — specifies the block driver to use for the given node. 👑
node-name — this defines the name of the block driver node by which it will be referenced later. The name must be unique, i.e. it must not match the name of a different block driver node, or (if you use -drive as well) the ID of a drive.

If no node name is specified, it is automatically generated. The generated node name is not intended to be predictable and changes between QEMU invocations. For the top level, an explicit node name must be specified. do not trust the auto-name, it's a different girl every time 💀

read-only — open the node read-only. Guest write attempts will fail. 🙅

Note that some block drivers support only read-only access, either generally or in certain configurations. In this case, the default value read-only=off does not work and the option must be specified explicitly. the default betrays you here, specify it yourself 😭

auto-read-only — bestie, if you set auto-read-only=on, QEMU gets permission to lowkey downgrade itself to read-only mode whenever it wants… even if you explicitly asked for read-only=off 😭. It can also flip between modes on the fly, like, depending on whether the image file is actually writable or whether some writing user is currently attached to the node. it's giving ✨flexible✨.
force-share — this one overrides QEMU's whole image locking system, forcing the node to run with weaker shared access in places where it would normally be demanding exclusive access 🔓. Here's the tea: whenever there's a chance multiple instances have the same file open — and it doesn't matter if this invocation of QEMU is the first or the second instance — both instances have to permit shared access for the second one to actually succeed at opening the file.

Heads up: turning on force-share=on requires read-only=on. no exceptions, bestie 💅

cache.direct — wanna dodge the host page cache entirely? cache.direct=on has you covered 🎀. It'll attempt to do disk IO directly to the guest's memory. Fair warning though: QEMU may still perform an internal copy of the data, so it's not fully direct-direct, yk?
cache.no-flush — okay so if you genuinely don't care about data integrity over host failures (iconic chaos, honestly 💀), you can use cache.no-flush=on. This tells QEMU it never needs to write any data to the disk and can just keep things chilling in cache instead. But listen — if anything goes wrong, like your host losing power, the disk storage getting disconnected accidentally, etc., your image will most probably be rendered unusable 😭. proceed at your own risk, fr fr.
discard=discard — discard is one of "ignore" (or "off") or "unmap" (or "on"), and it controls whether discard requests — also known as trim or unmap — get ignored or passed through to the filesystem 🗑️. Some machine types may not support discard requests at all, so vibe check your setup first.
detect-zeroes=detect-zeroes — detect-zeroes is "off", "on" or "unmap", and it enables the automatic conversion of plain zero writes by the OS into driver specific optimized zero write commands ⚡. You can even pick "unmap" if discard is set to "unmap", which lets a zero write get converted into an unmap operation. so efficient, we love to see it 🫶.

🌸 Driver-specific options for `file` 🌸

This is the protocol-level block driver for accessing regular files 📁.

filename — the path to the image file in the local filesystem.
aio — specifies the AIO backend (threads/native/io_uring, default: threads).
locking — specifies whether the image file is protected with Linux OFD / POSIX locks 🔐. The default is to use the Linux Open File Descriptor API if available, otherwise no lock is applied. (auto/on/off, default: auto).

Example:

-blockdev driver=file,node-name=disk,filename=disk.img

✨ Driver-specific options for `raw` ✨

This is the image format block driver for raw images 🦋. It is usually stacked on top of a protocol level block driver such as file.

file — reference to or definition of the data source block driver node (e.g. a file driver node).

Example 1:

-blockdev driver=file,node-name=disk_file,filename=disk.img
-blockdev driver=raw,node-name=disk,file=disk_file

Example 2:

-blockdev driver=raw,node-name=disk,file.driver=file,file.filename=disk.img

👑 Driver-specific options for `qcow2` 👑

This is the image format block driver for qcow2 images 💖. It is usually stacked on top of a protocol level block driver such as file.

file — reference to or definition of the data source block driver node (e.g. a file driver node).
backing — reference to or definition of the backing file block device (default is taken from the image file). It is allowed to pass null here in order to disable the default backing file.
lazy-refcounts — whether to enable the lazy refcounts feature (on/off; default is taken from the image file).
cache-size — the maximum total size of the L2 table and refcount block caches in bytes (default: the sum of l2-cache-size and refcount-cache-size).
l2-cache-size — the maximum size of the L2 table cache in bytes (default: if cache-size is not specified — 32M on Linux platforms, and 8M on non-Linux platforms; otherwise, as large as possible within the cache-size, while permitting the requested or the minimal refcount cache size).
refcount-cache-size — the maximum size of the refcount block cache in bytes (default: 4 times the cluster size; or if cache-size is specified, the part of it which is not used for the L2 cache).
cache-clean-interval — clean unused entries in the L2 and refcount caches 🧹. The interval is in seconds. The default value is 600 on supporting platforms, and 0 on other platforms. Setting it to 0 disables this feature.
pass-discard-request — whether discard requests to the qcow2 device should be forwarded to the data source (on/off; default: on if discard=unmap is specified, off otherwise).
pass-discard-snapshot — whether discard requests for the data source should be issued when a snapshot operation (e.g. deleting a snapshot) frees clusters in the qcow2 file (on/off; default: on).
pass-discard-other — whether discard requests for the data source should be issued on other occasions where a cluster gets freed (on/off; default: off).
discard-no-unref — when enabled, data clusters will remain preallocated when they are no longer used, e.g. because they are discarded or converted to zero clusters 💅. As usual, whether the old data is discarded or kept on the protocol level (i.e. in the image file) depends on the setting of the pass-discard-request option. Keeping the clusters preallocated prevents qcow2 fragmentation that would otherwise be caused by freeing and re-allocating them later. Besides potential performance degradation, such fragmentation can lead to increased allocation of clusters past the end of the image file, resulting in image files whose file length can grow much larger than their guest disk size would suggest. If image file length is of concern (e.g. when storing qcow2 images directly on block devices), you should consider enabling this option.
overlap-check — which overlap checks to perform for writes to the image (none/constant/cached/all; default: cached). For details or finer granularity control refer to the QAPI documentation of blockdev-add.

Example 1:

-blockdev driver=file,node-name=my_file,filename=/tmp/disk.qcow2
-blockdev driver=qcow2,node-name=hda,file=my_file,overlap-check=none,cache-size=16777216

Example 2:

-blockdev driver=qcow2,node-name=disk,file.driver=http,file.filename=http://example.com/image.qcow2

🦋 Driver-specific options for other drivers 🦋

Please refer to the QAPI documentation of the blockdev-add QMP command. that's the plug, bestie, iykyk 💜

🔥 `-drive option[,option[,option[,...]]]` 🔥

Define a new drive, periodt 💅. This includes creating a block driver node (the backend) and a guest device, and it's mostly a shortcut for defining the corresponding -blockdev and -device options. main character energy fr.

-drive accepts all options that are accepted by -blockdev. In addition, it knows the following options:

file=file — this option defines which disk image (see the Disk Images <#disk-images> chapter in the System Emulation Users Guide) to use with this drive 📀. If the filename contains a comma, you must double it (for instance, "file=my,,file" to use file "my,file"). Special files such as iSCSI devices can be specified using protocol specific URLs. See the section for "Device URL Syntax" for more information.
if=interface — this option defines on which type on interface the drive is connected 🔌. Available types are: ide, scsi, sd, mtd, floppy, pflash, virtio, none.
bus=bus,unit=unit — these options define where is connected the drive by defining the bus number and the unit id 📍.
index=index — this option defines where the drive is connected by using an index in the list of available connectors of a given interface type.
media=media — this option defines the type of the media: disk or cdrom 💿.
snapshot=snapshot — snapshot is "on" or "off" and controls snapshot mode for the given drive (see -snapshot) 📸.
cache=cache — bestie, this one decides how the host cache gets used to poke at block data. cache can be none, writeback, unsafe, directsync or writethrough. It's a lil shortcut that sets the cache.direct and cache.no-flush options (just like in -blockdev), and also cache.writeback, which hands out a default for the write-cache option of block guest devices (like in -device). The modes line up like this:
- writeback — cache.writeback=on, cache.direct=off, cache.no-flush=off
- none — cache.writeback=on, cache.direct=on, cache.no-flush=off
- writethrough — cache.writeback=off, cache.direct=off, cache.no-flush=off
- directsync — cache.writeback=off, cache.direct=on, cache.no-flush=off
- unsafe — cache.writeback=on, cache.direct=off, cache.no-flush=on

The default mode is cache=writeback. 🫶

aio=aio — aio is threads, native, or io_uring, and it picks between pthread based disk I/O, native Linux AIO, or the Linux io_uring API. Pick your fighter ✨
format=format — tell it exactly which disk format to use instead of letting it auto-detect. You can use this to specify format=raw to avoid interpreting an untrusted format header. (Safety queen behaviour, ngl 💅)
werror=action,rerror=action — say what to do on write and read errors. The valid actions are:
- ignore — ignore the error and try to continue
- stop — pause QEMU
- report — report the error to the guest
- enospc — pause QEMU only if the host disk is full; report the error to the guest otherwise

The default setting is werror=enospc and rerror=report.

copy-on-read=copy-on-read — copy-on-read is on or off and enables whether to copy read backing file sectors into the image file.
bps=b,bps_rd=r,bps_wr=w — set bandwidth throttling limits in bytes per second, either for all request types or just reads or just writes. Heads up: small values can lead to timeouts or hangs inside the guest. A safe minimum for disks is 2 MB/s.
bps_max=bm,bps_rd_max=rm,bps_wr_max=wm — set bursts in bytes per second, again either for all request types or for reads or writes only. Bursts let the guest I/O spike above the limit temporarily. Let it breathe, bestie 😌
iops=i,iops_rd=r,iops_wr=w — set request rate limits in requests per second, either for all request types or for reads or writes only.
iops_max=bm,iops_rd_max=rm,iops_wr_max=wm — set bursts in requests per second, either for all request types or for reads or writes only. Bursts let the guest I/O spike above the limit temporarily.
iops_size=is — let every is bytes of a request count as a new request for iops throttling purposes. Use this so guests can't dodge iops limits by sending fewer but larger requests. Sneaky guests stay losing 🔥
group=g — join a throttling quota group with the given name g. All drives that are members of the same group are accounted for together. Use this to stop guests from circumventing throttling limits by using many small disks instead of a single larger disk.

By default, the cache.writeback=on mode is used. It reports data writes as completed as soon as the data is present in the host page cache. That's safe as long as your guest OS makes sure to correctly flush disk caches where needed. But — and this is the part where you listen — if your guest OS does not handle volatile disk write caches correctly and your host crashes or loses power, then the guest may experience data corruption. 😭

For such guests, you should consider using cache.writeback=off. That means the host page cache is still used to read and write data, but the write notification gets sent to the guest only after QEMU has made sure to flush each write to the disk. Be aware that this has a major impact on performance. It's giving sacrifice for safety fr fr.

When using the -snapshot option, unsafe caching is always used.

Copy-on-read avoids accessing the same backing file sectors repeatedly and is useful when the backing file is over a slow network. By default copy-on-read is off.

Instead of -cdrom you can use:

qemu-system-x86_64 -drive file=file,index=2,media=cdrom

Instead of -hda, -hdb, -hdc, -hdd, you can use:

qemu-system-x86_64 -drive file=file,index=0,media=disk
qemu-system-x86_64 -drive file=file,index=1,media=disk
qemu-system-x86_64 -drive file=file,index=2,media=disk
qemu-system-x86_64 -drive file=file,index=3,media=disk

You can open an image using pre-opened file descriptors from an fd set:

qemu-system-x86_64 \
 -add-fd fd=3,set=2,opaque="rdwr:/path/to/file" \
 -add-fd fd=4,set=2,opaque="rdonly:/path/to/file" \
 -drive file=/dev/fdset/2,index=0,media=disk

You can connect a CDROM to the slave of ide0:

qemu-system-x86_64 -drive file=file,if=ide,index=1,media=cdrom

If you don't specify the "file=" argument, you define an empty drive:

qemu-system-x86_64 -drive if=ide,index=1,media=cdrom

Instead of -fda, -fdb, you can use:

qemu-system-x86_64 -drive file=file,index=0,if=floppy
qemu-system-x86_64 -drive file=file,index=1,if=floppy

By default, interface is "ide" and index is automatically incremented:

qemu-system-x86_64 -drive file=a -drive file=b

is interpreted like:

qemu-system-x86_64 -hda a -hdb b

🌸 `-mtdblock` file 🌸

Use file as on-board Flash memory image.

🎀 `-sd` file 🎀

Use file as SecureDigital card image.

🦋 `-snapshot` 🦋

Write to temporary files instead of disk image files. In this case, the raw disk image you use is not written back. You can however force the write back by pressing C-a s (see the Disk Images <#disk-images> chapter in the System Emulation Users Guide).

⚠️ Warning: snapshot is incompatible with -blockdev (instead use qemu-img to manually create snapshot images to attach to your blockdev). If you have mixed -blockdev and -drive declarations you can use the 'snapshot' property on your drive declarations instead of this global option. No cap, read this twice 🙈

✨ `-fsdev` ✨

-fsdev local,id=id,path=path,security_model=security_model
[,writeout=writeout][,readonly=on][,fmode=fmode][,dmode=dmode]
[,throttling.option=value[,throttling.option=value[,...]]]

-fsdev synth,id=id[,readonly=on]

Define a new file system device. Valid options are:

local — Accesses to the filesystem are done by QEMU.
synth — Synthetic filesystem, only used by QTests.
id=id — Specifies identifier for this device.
path=path — Specifies the export path for the file system device. Files under this path will be available to the 9p client on the guest.
security_model=security_model — Specifies the security model to be used for this export path. Supported security models are "passthrough", "mapped-xattr", "mapped-file" and "none". In "passthrough" security model, files are stored using the same credentials as they are created on the guest. This requires QEMU to run as root. In "mapped-xattr" security model, some of the file attributes like uid, gid, mode bits and link target are stored as file attributes. For "mapped-file" these attributes are stored in the hidden .virtfs_metadata directory. Directories exported by this security model cannot interact with other unix tools. "none" security model is same as passthrough except the sever won't report failures if it fails to set file attributes like ownership. Security model is mandatory only for local fsdriver.
writeout=writeout — This is an optional argument. The only supported value is "immediate". This means that host page cache will be used to read and write data but write notification will be sent to the guest only when the data has been reported as written by the storage subsystem.
readonly=on — Enables exporting 9p share as a readonly mount for guests. By default read-write access is given.
fmode=fmode — Specifies the default mode for newly created files on the host. Works only with security models "mapped-xattr" and "mapped-file".
dmode=dmode — sets the default mode for directories that get created fresh on the host 💅. Heads up: this only does anything with the "mapped-xattr" and "mapped-file" security models, no cap.
throttling.bps-total=b,throttling.bps-read=r,throttling.bps-write=w — caps your bandwidth in bytes per second 🐢, either for literally every request type, or just reads, or just writes. Your call bestie.
throttling.bps-total-max=bm,bps-read-max=rm,bps-write-max=wm — same deal but for bursts, in bytes per second ✨. Bursts let the guest I/O spike above the limit for a lil minute, like a lil treat. Either all request types or reads/writes only.
throttling.iops-total=i,throttling.iops-read=r,throttling.iops-write=w — request rate limits in requests per second 📈, for everything, or reads only, or writes only.
throttling.iops-total-max=im,throttling.iops-read-max=irm,throttling.iops-write-max=iwm — burst limits in requests per second 🌸, all types or reads/writes only. Again: bursts = guest I/O gets to pop off above the limit temporarily.
throttling.iops-size=is — every is bytes of a request counts as a brand new request for iops throttling purposes 🧮.

The -fsdev option is used along with the -device driver "virtio-9p-..." 🫶. They're a matched set, don't split them up.

`-device virtio-9p-type,fsdev=id,mount_tag=mount_tag` 💖

Ok so the options for the virtio-9p-... driver are:

type — picks which variant you're using 👑. The supported values are "pci", "ccw" or "device", and which one you want depends on your machine type.
fsdev=id — hands over the id value you specified next to the -fsdev option 🔗.
mount_tag=mount_tag — the tag name the guest uses to mount this export point 🏷️.

`-virtfs local,path=path,mount_tag=mount_tag,security_model=security_model[,writeout=writeout][,readonly=on][,fmode=fmode][,dmode=dmode][,multidevs=multidevs]`

`-virtfs synth,mount_tag=mount_tag`

Defines a whole new virtual filesystem device and shows it off to the guest using a virtio-9p-device (a.k.a. 9pfs 🌈). Basically: a directory on the host becomes directly accessible by the guest as a pass-through file system, using the 9P network protocol to chat between host and guests 🦋. And if you want? Several guests can even share it at the same time. Iconic.

Ngl, -virtfs is literally just a convenience shortcut for the generalized form -fsdev -device virtio-9p-pci 💅.

The general form of pass-through file system options goes like this:

local — QEMU itself does the filesystem accesses 🙋.
synth — synthetic filesystem, only used by QTests 🧪.
id=id — specifies the identifier for the filesystem device 🆔.
path=path — the export path for the file system device 📁. Files under this path will be available to the 9p client on the guest.
security_model=security_model — which security model to use for this export path 🔐. Supported models are "passthrough", "mapped-xattr", "mapped-file" and "none". In "passthrough", files are stored using the same credentials as they're created with on the guest — which requires QEMU to run as root, so, yeah, be aware 😭. In "mapped-xattr", some file attributes like uid, gid, mode bits and link target get stored as file attributes ✨. For "mapped-file" those attributes go in the hidden .virtfs_metadata directory, and heads up: directories exported by this security model cannot interact with other unix tools 💀. "none" is the same as passthrough except the server won't report failures if it can't set file attributes like ownership 🙈. Security model is mandatory only for local fsdriver.
writeout=writeout — optional argument, bestie, and the only supported value is "immediate" ⏱️. What it means: the host page cache gets used to read and write data, but the write notification only gets sent to the guest once the data has been reported as written by the storage subsystem.
readonly=on — exports the 9p share as a read-only mount for guests 🔒. By default you get read-write access.
fmode=fmode — the default mode for files newly created on the host 🎀. Only works with the "mapped-xattr" and "mapped-file" security models.
dmode=dmode — the default mode for directories newly created on the host 📂. Same deal: only "mapped-xattr" and "mapped-file".
mount_tag=mount_tag — the tag name the guest uses to mount this export point 🏷️.
multidevs=remap|forbid|warn — how to deal with multiple devices being shared with the same 9p export, so you can dodge file ID collisions on the guest 👯. Supported behaviours are "remap" (the default), "forbid" or "warn".
- remap : assumes there's a possibility that more than one device is shared with the same 9p export 🌀. So inode numbers from the host get remapped for the guest in a way that prevents file ID collisions on the guest. This remapping is required in such cases because the original device IDs from the host are never passed and exposed on the guest — instead, all files of an export shared with virtfs always share the same device ID on the guest. So two files with identical inode numbers but from actually different devices on the host would otherwise cause a file ID collision and therefore potential severe misbehaviours on the guest 😭.
- warn : virtfs 9p expects only one device to be shared with the same export 👀. If more than one device is shared and accessed via the same 9p export, then only a warning message gets logged (once) by qemu on the host side. No further action is performed that would prevent file ID collisions on the guest. So this could lead to severe misbehaviours — like wrong files being accessed and data corruption on the exported tree 💀.
- forbid : assumes, like "warn", that only one device is shared by the same 9p export — but it won't just log a warning, it'll also deny access to additional devices on the guest 🚫. Note though that "forbid" does currently not block all possible file access operations (e.g. readdir() would still return entries from other devices) 🙈.
-iscsi — configure iSCSI session parameters 🔥.

✨ USB convenience options ✨

`-usb`

Enables USB emulation on machine types that have an on-board USB host controller (if it isn't already enabled by default) 🔌. Ngl though: on-board USB host controllers may not support USB 3.0 💀. In that case, -device qemu-xhci can be used instead on machines with PCI 💅.

`-usbdevice devname`

Adds the USB device devname, and enables an on-board USB controller if that's possible and necessary (just like it can be done via -machine usb=on) 🫶. Note that this option is mainly intended for the user's convenience only — more fine-grained control can be achieved by selecting a USB host controller (if necessary) and the desired USB device via the -device option instead 👑. For example, instead of using -usbdevice mouse it's possible to use -device qemu-xhci -device usb-mouse to connect the USB mouse to a USB 3.0 controller instead (at least on machines that support PCI and do not have a USB controller enabled by default yet) 🌈. For more details, see the chapter about Connecting USB devices <#connecting-usb-devices> in the System Emulation Users Guide 📖. Possible devices for devname are:

braille — Braille device 👁️. This will use BrlAPI to display the braille output on a real or fake device (i.e. it also creates a corresponding braille chardev automatically beside the usb-braille USB device).
keyboard — Standard USB keyboard ⌨️. Will override the PS/2 keyboard (if present).
mouse — Virtual Mouse 🖱️. This will override the PS/2 mouse emulation when activated.
tablet — Pointer device that uses absolute coordinates (like a touchscreen) ✍️. This means QEMU is able to report the mouse position without having to grab the mouse. Also overrides the PS/2 mouse emulation when activated.
wacom-tablet — Wacom PenPartner USB tablet 🖊️.

🌸 Display options 🌸

`-display type`

Selects the type of display to use 👀. Use -display help to list the available display types. Valid values for type are:

spice-app[,gl=on|off] — starts QEMU as a Spice server and launches the default Spice client application 🌶️. The Spice server will redirect the serial consoles and QEMU monitors. (Since 4.0)
dbus — export the display over D-Bus interfaces 🚌. (Since 7.0)

The connection is registered with the "org.qemu" name (and queued when already owned) 💅.

addr=<dbusaddr> : D-Bus bus address to connect to 🔌.
p2p=yes|no : use peer-to-peer connection, accepted via QMP add_client 🤝.
gl=on|off|core|es : use OpenGL for rendering (the D-Bus interface will share framebuffers with DMABUF file descriptors) 🎨.

sdl — display video output via SDL (usually in a separate graphics window; see the SDL documentation for other possibilities) 🖼️. Valid parameters are:
- grab-mod=<mods> : used to select the modifier keys for toggling the mouse grabbing in conjunction with the "g" key 🖱️. <mods> can be either lshift-lctrl-lalt or rctrl.
- gl=on|off|core|es : use OpenGL for displaying ✨.
- show-cursor=on|off : force showing the mouse cursor 👆.
window-close=on|off — let qemu dip out when you hit the window close button 💅
gtk — shows the video output in a GTK window. This one's got drop-down menus and other UI bits so you can tweak and control the VM while it's running. The valid params are:
- full-screen=on|off — start off in fullscreen mode
- gl=on|off — use OpenGL for displaying
- grab-on-hover=on|off — grab keyboard input the moment the mouse hovers over
- show-tabs=on|off — show the tab bar for switching between the various graphical interfaces (think VGA and virtual console character devices), on by default
- show-cursor=on|off — force the mouse cursor to stay visible
- window-close=on|off — let qemu quit when you hit the window close button
- show-menubar=on|off — show the main window menubar, defaults to "on"
- zoom-to-fit=on|off — expand the video output to fill the window size, defaults to "off"
curses[,charset=<encoding>] — render the video output through curses ✨. For graphics device models that support a text mode, QEMU can show that output using a curses/ncurses interface. Nothing shows up when the graphics device is in graphical mode, or if it just doesn't do text mode at all. Ngl it's generally only the VGA device models that support text mode. You can tell it which font charset the guest uses via the charset option — like charset=CP850 for IBM CP850 encoding. The default is CP437.
cocoa — shows the video output in a Cocoa window. Mac only 🍎. This interface gives you drop-down menus and other UI bits to configure and control the VM at runtime. Valid params are:
- full-grab=on|off — capture all key presses, system combos included. Heads up bestie, this needs accessibility permissions, since it does a global grab on key events. (default: off) See <https://support.apple.com/en-in/guide/mac-help/mh32356/mac>
- swap-opt-cmd=on|off — swap the Option and Command keys so their key codes line up with where they sit on non-Mac keyboards, and you can use Meta/Super and Alt exactly where you'd expect. (default: off)
- show-cursor=on|off — force the mouse cursor to stay visible
- left-command-key=on|off — disable forwarding the left command key to the host
- full-screen=on|off — start off in fullscreen mode
- zoom-to-fit=on|off — expand the video output to fill the window size, defaults to "off"
egl-headless[,rendernode=<file>] — offload all the OpenGL operations to a local DRI device. For any graphical display, this one needs to be paired up with either VNC or SPICE displays.
vnc=<display> — start a VNC server on display <display>
none — don't display video output at all. The guest still sees an emulated graphics card, but its output never gets shown to the QEMU user. This is not the same as -nographic — none only touches what happens with video output, whereas -nographic also changes where the serial and parallel port data goes.

-nographic 🙈

So normally, if QEMU was compiled with graphical window support, it shows stuff like guest graphics, the guest console, and the QEMU monitor in a window. With this option you can totally kill the graphical output and make QEMU a plain old command line app. The emulated serial port gets redirected onto the console and muxed with the monitor (unless you explicitly redirect it somewhere else). Which means you can still use QEMU to debug a Linux kernel with a serial console, slay. Hit C-a h for help on switching between the console and the monitor 👑

-spice option[,option[,...]] 🌶️

Turn on the spice remote desktop protocol. The valid options are:

port=<nr> — set the TCP port spice listens on for plaintext channels
addr=<addr> — set the IP address spice listens on. Default is any address.
ipv4=on|off; ipv6=on|off; unix=on|off — force using the specified IP version
password-secret=<secret-id> — set the ID of the secret object holding the password you need for auth
sasl=on|off — require the client to use SASL to authenticate with spice. The exact auth method picked is controlled from the system/user's SASL config file for the 'qemu' service. That's typically hanging out in /etc/sasl2/qemu.conf. If you're running QEMU as an unprivileged user, you can set the environment variable SASL_CONF_PATH to make it look in alternate spots for the service config. And like, while some SASL auth methods can also do data encryption (eg GSSAPI), it's recommended that SASL always be combined with the 'tls' and 'x509' settings so SSL and server certificates are on. That ensures data encryption, which stops your auth credentials from getting compromised. No cap 🔒
disable-ticketing=on|off — allow clients to connect with no authentication
disable-copy-paste=on|off — kill copy paste between the client and the guest
disable-agent-file-xfer=on|off — kill spice-vdagent based file-xfer between the client and the guest
tls-port=<nr> — set the TCP port spice listens on for encrypted channels
x509-dir=<dir> — set the x509 file directory. Expects the same filenames as -vnc $display,x509=$dir
x509-key-file=<file>; x509-key-password=<file>; x509-cert-file=<file>; x509-cacert-file=<file>; x509-dh-key-file=<file> — the x509 file names can also be configured individually
tls-ciphers=<list> — specify which ciphers to use
tls-channel=[main|display|cursor|inputs|record|playback]; plaintext-channel=[main|display|cursor|inputs|record|playback] — force a specific channel to be used with or without TLS encryption. You can specify these options multiple times to configure multiple channels. The special name "default" sets the default mode. For channels that aren't explicitly forced into one mode, the spice client gets to pick tls/plaintext however it pleases.
image-compression=[auto_glz|auto_lz|quic|glz|lz|off] — configure image compression (lossless). Default is auto_glz.
jpeg-wan-compression=[auto|never|always]; zlib-glz-wan-compression=[auto|never|always] — configure wan image compression (lossy for slow links). Default is auto.
streaming-video=[off|all|filter] — configure video stream detection. Default is off.
agent-mouse=[on|off] — enable/disable passing mouse events via vdagent. Default is on.
playback-compression=[on|off] — enable/disable audio stream compression (using celt 0.5.1). Default is on.
seamless-migration=[on|off] — enable/disable spice seamless migration. Default is off.
video-codec=<codec> — give the preferred codec the Spice server should use with the Gstreamer encoder. This one only matters when gl=on is specified. If no codec is provided, then the codec gstreamer:h264 gets used as default. And for the case where gl=off, the default codec used is determined by the Spice server.
max-refresh-rate=rate — give the maximum refresh rate (or FPS) at which the encoding requests get sent to the Spice server. The default would be 30.
gl=[on|off] — enable/disable the OpenGL context. Default is off.
rendernode=<file> — DRM render node for OpenGL rendering. If you don't specify it, it'll pick the first available one. (Since 2.9)

-vga type 🎨

Pick which type of VGA card to emulate. The valid values for type are:

cirrus — Cirrus Logic GD5446 Video card. Every Windows version starting from Windows 95 should recognize and use this graphic card. For optimal performance, use 16 bit color depth in the guest and the host OS. (This card was the default before QEMU 2.2)
std — Standard VGA card with Bochs VBE extensions. If your guest OS supports the VESA 2.0 VBE extensions (like Windows XP) and you wanna run high resolution modes (>= 1280x1024x16) then this is the one you want. (This card is the default since QEMU 2.2)
vmware — VMWare SVGA-II compatible adapter. Use it if you've got a sufficiently recent XFree86/XOrg server, or a Windows guest with a driver for this card.
qxl — QXL paravirtual graphic card. It's VGA compatible (VESA 2.0 VBE support included). Works best with qxl guest drivers installed though. Recommended choice when you're using the spice protocol 💖
tcx — (sun4m only) Sun TCX framebuffer. This is the default framebuffer for sun4m machines and offers both 8-bit and 24-bit colour depths at a fixed resolution of 1024x768.
cg3 — (sun4m only) Sun cgthree framebuffer. A simple 8-bit framebuffer for sun4m machines, available in both 1024x768 (OpenBIOS) and 1152x900 (OBP) resolutions, aimed at people wishing to run older Solaris versions.
virtio — Virtio VGA card.
none — disable the VGA card.

-full-screen 🖥️✨

Start in full screen. That's it, that's the whole thing.

-g widthxheight[xdepth] — sets the initial graphical resolution and depth. PPC and SPARC only, bestie, so don't come for me if x86 ignores it 💅

For PPC the default is 800x600x32.

For SPARC with the TCX graphics device, the default is 1024x768x8 with the option of 1024x768x24. For cgthree, the default is 1024x768x8 with the option of 1152x900x8 for people who wish to use OBP.

-vnc display[,option[,option[,...]]] — okay so normally, if QEMU is compiled with graphical window support, it shows you stuff like guest graphics, the guest console, and the QEMU monitor in a window. With this option you can make QEMU listen on VNC display display and redirect the VGA display over the VNC session. Iconic. It's very useful to enable the usb tablet device when you use this (that's the -device usb-tablet option, iykyk). And when you're using the VNC display, you must use the -k parameter to set the keyboard layout if you're not using en-us. Valid syntax for the display is:
- to=L — with this option, QEMU will try the next available VNC displays, until the number L, if the originally defined -vnc display is not available — like, say, port 5900+display is already being used by another application. By default, to=0.
- host:d — TCP connections will only be allowed from host on display d. By convention the TCP port is 5900+d. Optionally, host can be omitted, in which case the server will accept connections from any host.
- unix:path — connections will be allowed over UNIX domain sockets, where path is the location of a unix socket to listen for connections on.
- none — VNC is initialized but not started. The monitor change command can be used to later start the VNC server. girl you can turn it on whenever, no rush ✨

Following the display value there may be one or more option flags separated by commas. Valid options are:

reverse=on|off — connect to a listening VNC client via a "reverse" connection. The client is specified by the display. For reverse network connections (host:d,reverse), the d argument is a TCP port number, not a display number. 🫶
websocket=on|off — opens an additional TCP listening port dedicated to VNC Websocket connections. If a bare websocket option is given, the Websocket port is 5700+display. An alternative port can be specified with the syntax websocket=port.

If host is specified, connections will only be allowed from this host. It's possible to control the websocket listen address independently, using the syntax websocket=host:port.

Websocket could be allowed over UNIX domain socket, using the syntax websocket=unix:path, where path is the location of a unix socket to listen for connections on.

If no TLS credentials are provided, the websocket connection runs in unencrypted mode. If TLS credentials are provided, the websocket connection requires encrypted client connections. 🔐

password=on|off — require that password based authentication is used for client connections.

The password must be set separately using the set_password command in the QEMU Monitor <#qemu-monitor>. The syntax to change your password is: set_password <protocol> <password> where <protocol> could be either "vnc" or "spice".

If you would like to change <protocol> password expiration, you should use expire_password <protocol> <expiration-time> where expiration time could be one of the following options: now, never, +seconds or UNIX time of expiration, e.g. +60 to make password expire in 60 seconds, or 1335196800 to make password expire on "Mon Apr 23 12:00:00 EDT 2012" (UNIX time for this date and time).

You can also use the keywords "now" or "never" for the expiration time to allow <protocol> password to expire immediately or never expire. choose your own adventure tbh ⏰

password-secret=<secret-id> — require that password based authentication is used for client connections, using the password provided by the secret object identified by secret-id.
tls-creds=ID — provides the ID of a set of TLS credentials to use to secure the VNC server. They will apply to both the normal VNC server socket and the websocket socket (if enabled). Setting TLS credentials will cause the VNC server socket to enable the VeNCrypt auth mechanism. The credentials should have been previously created using the -object tls-creds argument. 💖
tls-authz=ID — provides the ID of the QAuthZ authorization object against which the client's x509 distinguished name will be validated. This object is only resolved at time of use, so it can be deleted and recreated on the fly while the VNC server is active. If missing, it will default to denying access.
sasl=on|off — require that the client use SASL to authenticate with the VNC server. The exact choice of authentication method used is controlled from the system / user's SASL configuration file for the 'qemu' service. This is typically found in /etc/sasl2/qemu.conf. If running QEMU as an unprivileged user, an environment variable SASL_CONF_PATH can be used to make it search alternate locations for the service config. While some SASL auth methods can also provide data encryption (eg GSSAPI), it is recommended that SASL always be combined with the 'tls' and 'x509' settings to enable use of SSL and server certificates. This ensures a data encryption preventing compromise of authentication credentials. See the VNC security <#vnc-security> section in the System Emulation Users Guide for details on using SASL authentication. 🎀
sasl-authz=ID — provides the ID of the QAuthZ authorization object against which the client's SASL username will be validated. This object is only resolved at time of use, so it can be deleted and recreated on the fly while the VNC server is active. If missing, it will default to denying access.
acl=on|off — legacy method for enabling authorization of clients against the x509 distinguished name and SASL username. It results in the creation of two authz-list objects with IDs of vnc.username and vnc.x509dname. The rules for these objects must be configured with the HMP ACL commands.

This option is deprecated and should no longer be used. The new sasl-authz and tls-authz options are a replacement. no cap, put it down 💀

lossy=on|off — enable lossy compression methods (gradient, JPEG, ...). If this option is set, the VNC client may receive lossy framebuffer updates depending on its encoding settings. Enabling this option can save a lot of bandwidth, at the expense of quality. 🍓
non-adaptive=on|off — disable adaptive encodings. Adaptive encodings are enabled by default. An adaptive encoding will try to detect frequently updated screen regions, and send updates in these regions using a lossy encoding (like JPEG). This can be really helpful to save bandwidth when playing videos. Disabling adaptive encodings restores the original static behavior of encodings like Tight.
share=[allow-exclusive|force-shared|ignore] — set display sharing policy. 'allow-exclusive' allows clients to ask for exclusive access. As suggested by the rfb spec this is implemented by dropping other connections. Connecting multiple clients in parallel requires all clients asking for a shared session (vncviewer: -shared switch). This is the default. 'force-shared' disables exclusive client access — useful for shared desktop sessions, where you don't want someone forgetting to specify -shared and disconnecting everybody else. 'ignore' completely ignores the shared flag and allows everybody to connect unconditionally. Doesn't conform to the rfb spec but is traditional QEMU behavior. 💅
key-delay-ms — set keyboard delay, for key down and key up events, in milliseconds. Default is 10. Keyboards are low-bandwidth devices, so this slowdown can help the device and guest to keep up and not lose events in case events are arriving in bulk. Possible causes for the latter are flaky network connections, or scripts for automated testing.
audiodev=audiodev — use the specified audiodev when the VNC client requests audio transmission. When not using an -audiodev argument, this option must be omitted, otherwise it must be present and specify a valid audiodev. 🔊
power-control=on|off — permit the remote client to issue shutdown, reboot or reset power control requests. 👑

🌈 i386 target only 🌈

-win2k-hack — use it when installing Windows 2000 to avoid a disk full bug. After Windows 2000 is installed, you no longer need this option (this option slows down the IDE transfers). Synonym of -global ide-device.win2k-install-hack=on. vintage behaviour fr fr
-no-fd-bootchk — disable boot signature checking for floppy disks in BIOS. May be needed to boot from old floppy disks. Synonym of -m fd-bootchk=off. 💾✨
-acpitable [sig=str][,rev=n][,oem_id=str][,oem_table_id=str][,oem_rev=n][,asl_compiler_id=str][,asl_compiler_rev=n][,data=file1[:file2]...] — drops in an ACPI table, with header fields you pick yourself and the actual content pulled from the files you name. For file=, QEMU yoinks the whole ACPI table straight out of the specified files, every ACPI header included (which other options can override, bestie). For data=, only the data portion gets used and all the header info has to come from the command line. And listen: if you hand QEMU a SLIC table, then the SLIC's oem_id and oem_table_id fields will straight-up override the same ones in the RSDT and the FADT (a.k.a. FACP), just so the field matches what the Microsoft SLIC spec and the ACPI spec require. slay 💅
-smbios file=binary — loads the SMBIOS entry from a binary file. easy peasy 🎀
-smbios type=0[,vendor=str][,version=str][,date=str][,release=%d.%d][,uefi=on|off] — sets the SMBIOS type 0 fields ✨
-smbios type=1[,manufacturer=str][,product=str][,version=str][,serial=str][,uuid=uuid][,sku=str][,family=str] — sets the SMBIOS type 1 fields 🌸
-smbios type=2[,manufacturer=str][,product=str][,version=str][,serial=str][,asset=str][,location=str] — sets the SMBIOS type 2 fields 🦋
-smbios type=3[,manufacturer=str][,version=str][,serial=str][,asset=str][,sku=str] — sets the SMBIOS type 3 fields 💖
-smbios type=4[,sock_pfx=str][,manufacturer=str][,version=str][,serial=str][,asset=str][,part=str][,processor-family=%d][,processor-id=%d] — sets the SMBIOS type 4 fields ⭐
-smbios type=9[,slot_designation=str][,slot_type=%d][,slot_data_bus_width=%d][,current_usage=%d][,slot_length=%d][,slot_id=%d][,slot_characteristics1=%d][,slot_characteristics12=%d][,pci_device=str] — sets the SMBIOS type 9 fields 🌈
-smbios type=11[,value=str][,path=filename] — sets the SMBIOS type 11 fields 👑

Okay so this one is a whole thing, so listen up: you can repeat this argument as many times as you want, and the values get added in the order they're parsed, no cap. Applications that wanna use OEM strings data are encouraged to use their own application name as a prefix for the value string — that way info for multiple applications can be passed in concurrently without it being a whole mess. very considerate of them fr fr 🫶

The value=str syntax gives you the string data inline, while path=filename loads data from a file on disk. Heads up though: that file is not permitted to contain any NUL bytes. 🚫

Both the value and path options can be repeated multiple times and will be added to the SMBIOS table in the order in which they appear.

And a warning bestie: on the x86 architecture, the total size of all SMBIOS tables is limited to 65535 bytes. So the OEM strings data is not suitable for passing large amounts of data into the guest — it's giving "hint", not "storage". Instead it should be used as an indicator to inform the guest where to locate the real data set, like, for example, by specifying the serial ID of a block device. 💀

An example passing three strings is

-smbios type=11,value=cloud-init:ds=nocloud-net;s=http://10.10.0.1:8000/,\
                value=anaconda:method=http://dl.fedoraproject.org/pub/fedora/linux/releases/25/x86_64/os,\
                path=/some/file/with/oemstringsdata.txt

In the guest OS this is visible with the dmidecode command

$ dmidecode -t 11
Handle 0x0E00, DMI type 11, 5 bytes
OEM Strings
     String 1: cloud-init:ds=nocloud-net;s=http://10.10.0.1:8000/
     String 2: anaconda:method=http://dl.fedoraproject.org/pub/fedora/linux/releases/25/x86_64/os
     String 3: myapp:some extra data

-smbios type=17[,loc_pfx=str][,bank=str][,manufacturer=str][,serial=str][,asset=str][,part=str][,speed=%d] — sets the SMBIOS type 17 fields 🍓
-smbios type=41[,designation=str][,kind=str][,instance=%d][,pcidev=str] — sets the SMBIOS type 41 fields 🧚

This argument can be repeated multiple times. Its main use is to allow network interfaces be created as enoX on Linux — with X being the instance number — instead of the name depending on the interface position on the PCI bus. iconic behaviour tbh 💜

Here is an example of use:

-netdev user,id=internet \
-device virtio-net-pci,mac=50:54:00:00:00:42,netdev=internet,id=internet-dev \
-smbios type=41,designation='Onboard LAN',instance=1,kind=ethernet,pcidev=internet-dev

In the guest OS, the device should then appear as eno1:

..parsed-literal:

$ ip -brief l
lo               UNKNOWN        00:00:00:00:00:00 <LOOPBACK,UP,LOWER_UP>
eno1             UP             50:54:00:00:00:42 <BROADCAST,MULTICAST,UP,LOWER_UP>

Currently, the PCI device has to be attached to the root bus. that's the rules, bestie 📌

🌐 Network options 🌐

-nic [tap|passt|bridge|user|l2tpv3|vde|netmap|af-xdp|vhost-user|socket][,...][,mac=macaddr][,model=mn] — this is the shortcut option, the "why do it in two steps" girlie of the networking world. It configures the on-board (default) guest NIC hardware and the host network backend in one go. ✨

The host backend options are exactly the same as with the corresponding -netdev options below. The guest NIC model gets set with model=modelname — and yes, model=help will list the available device types for you. The hardware MAC address is set with mac=macaddr. 💅

These following two examples do exactly the same thing, just to show off how -nic can shorten the command line length:

qemu-system-x86_64 -netdev user,id=n1,ipv6=off -device e1000,netdev=n1,mac=52:54:98:76:54:32
qemu-system-x86_64 -nic user,ipv6=off,model=e1000,mac=52:54:98:76:54:32

-nic none — says "no network devices should be configured, periodt." It's used to override the default configuration (default NIC with the "user" host network backend) that gets activated if no other networking options are provided. so if you forgot and QEMU went and gave you a NIC you didn't ask for, this is your girl 🚫
-netdev passt,id=str[,option][,...] — sets up a passt network backend, which needs zero administrator privilege to run. obsessed. valid options are: 👑
- id=id — assigns a symbolic name for use in monitor commands.
- path=file — the filename of the passt program to run. If it's not provided, the passt command will be started with the help of the PATH environment variable.
- quiet=on|off — by default, quiet=on, which disables informational messages from passt. quiet=on is passed as --quiet to passt.
- vhost-user=on|off — by default, vhost-user=off and QEMU uses the stream network backend to talk to passt. If vhost-user=on, passt is started with --vhost-user and QEMU uses the vhost-user network backend to communicate with passt.
- @mtu — assign MTU via DHCP/NDP
- address — IPv4 or IPv6 address
- netmask — IPv4 mask
- mac — source MAC address
- gateway — IPv4 or IPv6 address as gateway
- interface — interface for addresses and routes
- outbound — bind to address as outbound source
- outbound-if4 — bind to outbound interface for IPv4
- outbound-if6 — bind to outbound interface for IPv6
- dns — IPv4 or IPv6 address as DNS
- search — search domains
- fqdn — FQDN to configure client with
- dhcp-dns — enable/disable DNS list in DHCP/DHCPv6/NDP
- dhcp-search — enable/disable list in DHCP/DHCPv6/NDP
- map-host-loopback — addresse to refer to host
- map-guest-addr — addr to translate to guest's address
- dns-forward — forward DNS queries sent to
- dns-host — host nameserver to direct queries to
- tcp — enable/disable TCP
- udp — enable/disable UDP
- icmp — enable/disable ICMP
- dhcp — enable/disable DHCP
- ndp — enable/disable NDP
- dhcpv6 — enable/disable DHCPv6
- ra — enable/disable route advertisements
- freebind — bind to any address for forwarding
- ipv4 — enable/disable IPv4
- ipv6 — enable/disable IPv6
- tcp-ports — TCP ports to forward
- udp-ports — UDP ports to forward
- param=string — string will be passed to passt as a command line parameter, and we can have multiple occurrences of the param parameter to pass multiple parameters to passt.

For instance, to pass --trace --log=trace.log:

qemu-system-x86_64 -nic passt,param=--trace,param=--log=trace.log

-netdev user,id=id[,option][,option][,...] — sets up a user mode host network backend, which also needs no administrator privilege to run. iconic, we love not needing sudo 💖 valid options are:
- id=id — assigns a symbolic name for use in monitor commands.
- ipv4=on|off and ipv6=on|off — specify that either IPv4 or IPv6 must be enabled. If neither is specified, both protocols are enabled.
- net=addr[/mask] — set the IP network address the guest will see. You can optionally specify the netmask, either in the form a.b.c.d or as the number of valid top-most bits. Default is 10.0.2.0/24.
- host=addr — specify the guest-visible address of the host. Default is the 2nd IP in the guest network, i.e. x.x.x.2.
- ipv6-net=addr[/int] — set the IPv6 network address the guest will see (default is fec0::/64). The network prefix is given in the usual hexadecimal IPv6 address notation. The prefix size is optional, and is given as the number of valid top-most bits (default is 64).
- ipv6-host=addr — specify the guest-visible IPv6 address of the host. Default is the 2nd IPv6 in the guest network, i.e. xxxx::2.
- restrict=on|off — if this option is enabled, the guest gets isolated: it won't be able to contact the host, and no guest IP packets will be routed over the host to the outside. Heads up though — this option does not affect any explicitly set forwarding rules. 😭
- hostname=name — specifies the client hostname reported by the built-in DHCP server.

dhcpstart=addr — tells the built-in DHCP server where to start handing out IPs. It owns a little block of 16 IPs total, and this is the first one. Default? The 15th through 31st IP in the guest network, aka x.x.x.15 to x.x.x.31. ✨
dns=addr — sets the guest-visible address of the virtual nameserver, bestie. Heads up tho: this address has to be different from the host address or it's not gonna vibe. Default is the 3rd IP in the guest network, so x.x.x.3. 🎀
ipv6-dns=addr — same energy as dns but for IPv6. Sets the guest-visible address of the IPv6 virtual nameserver, and yeah, it must be different from the host address too. Default is the 3rd IP in the guest network: xxxx::3. 🦋
dnssearch=domain — drops an entry into the domain-search list that the built-in DHCP server sends out. Wanna send more than one suffix? Just pass this option multiple times, no cap. If the guest supports it, it'll auto-try appending those suffixes whenever a domain name won't resolve. iconic. 💅

Example:

qemu-system-x86_64 -nic user,dnssearch=mgmt.example.org,dnssearch=example.org

domainname=domain — sets the client domain name that the built-in DHCP server reports. 🍓
tftp=dir — with the user mode network stack, this activates a built-in TFTP server and exposes the files in dir as its root. Your guest's TFTP client must be in binary mode (that's the bin command in the Unix TFTP client, iykyk). This server is read-only — it has no command for writing files, and QEMU will not write to this directory. periodt. 🔒
tftp-server-name=name — in the BOOTP reply, this broadcasts name as the "TFTP server name" (RFC2132 option 66). Handy for telling the guest to load boot files or configs from a different server than the host address. 🌈
bootfile=file — with the user mode network stack, this broadcasts file as the BOOTP filename. Pair it with tftp and you can network boot a guest straight from a local directory. main character energy fr fr. 👑

Example (using pxelinux):

qemu-system-x86_64 -hda linux.img -boot n -device e1000,netdev=n1 \
    -netdev user,id=n1,tftp=/path/to/tftp/files,bootfile=/pxelinux.0

smb=dir[,smbserver=addr] — with the user mode network stack, this fires up a built-in SMB server so Windows OSes can transparently reach the host files in dir. You can pin the SMB server's IP to addr; default is the 4th IP in the guest network, aka x.x.x.4. 🫶

In the guest Windows OS, you gotta add this line:

10.0.2.4 smbserver

into the file C:\WINDOWS\LMHOSTS (for Windows 9x/Me) or C:\WINNT\SYSTEM32\DRIVERS\ETC\LMHOSTS (Windows NT/2000).

Then dir is reachable at \\smbserver\qemu. 🎉

Lowkey important: a SAMBA server must be installed on the host OS.

hostfwd=[tcp|udp|unix]:[[hostaddr]:hostport|hostpath]-[guestaddr]:guestport — redirects incoming TCP, UDP, or UNIX connections hitting the host port hostport over to guest IP guestaddr on guest port guestport. If you don't specify guestaddr, it defaults to x.x.x.15 (the default first address the built-in DHCP server hands out). Specify hostaddr and you can bind the rule to a specific host interface. No connection type set? TCP it is. You can pass this option multiple times. ✨

For example, to redirect a host X11 connection from screen 1 to guest screen 0:

# on the host
qemu-system-x86_64 -nic user,hostfwd=tcp:127.0.0.1:6001-:6000
# this host xterm should open in the guest X11 server
xterm -display :1

To redirect telnet connections from host port 5555 to the telnet port on the guest:

# on the host
qemu-system-x86_64 -nic user,hostfwd=tcp::5555-:23
telnet localhost 5555

Then when you run telnet localhost 5555 on the host, boom — you're connected to the guest telnet server. 💖

To redirect host unix socket /tmp/vm to guest tcp socket 23:

# on the host
qemu-system-x86_64 -nic user,hostfwd=unix:/tmp/vm-:23

guestfwd=[tcp]:server:port-dev;
guestfwd=[tcp]:server:port-cmd:command — forwards guest TCP connections to the IP server on port port, sending them to the character device dev or to a program run by cmd:command (which gets spawned fresh for each connection). You can give this option multiple times. 🧚

Option A: use a chardev directly and have that one used for QEMU's whole lifetime, like so:

# open 10.10.1.1:4321 on bootup, connect 10.0.2.100:1234 to it whenever
# the guest accesses it
qemu-system-x86_64 -nic user,guestfwd=tcp:10.0.2.100:1234-<tcp:10.10.1.1:4321>

Option B: run a command on every single TCP connection the guest makes, so QEMU acts kinda like an inetd process for that virtual server:

# call "netcat 10.10.1.1 4321" on every TCP connection to 10.0.2.100:1234
# and connect the TCP stream to its stdin/stdout
qemu-system-x86_64 -nic  'user,id=n1,guestfwd=tcp:10.0.2.100:1234-cmd:netcat 10.10.1.1 4321'

OPTIONS (cont.) — the netdev era 🕸️

`-netdev` 🛠️

tap,id=id[,fd=h][,ifname=name][,script=file][,downscript=dfile][,br=bridge][,helper=helper] — configures a host TAP network backend with ID id. 🫧

It uses the network script file file to set it up and the network script dfile to tear it down. Don't give a name? The OS just auto-provides one, no stress. The default network configure script is /etc/qemu-ifup and the default network deconfigure script is /etc/qemu-ifdown. Wanna skip scripts entirely? Use script=no or downscript=no to disable script execution. 💅

If you're running QEMU as an unprivileged user, use the network helper to configure the TAP interface and attach it to the bridge. The default network helper executable is /usr/lib/qemu/qemu-bridge-helper and the default bridge device is br0. 🌉

fd=h lets you specify the handle of an already-opened host TAP interface.

Examples:

#launch a QEMU instance with the default network script
qemu-system-x86_64 linux.img -nic tap

#launch a QEMU instance with two NICs, each one connected
#to a TAP device
qemu-system-x86_64 linux.img \
        -netdev tap,id=nd0,ifname=tap0 -device e1000,netdev=nd0 \
        -netdev tap,id=nd1,ifname=tap1 -device rtl8139,netdev=nd1

#launch a QEMU instance with the default network helper to
#connect a TAP device to bridge br0
qemu-system-x86_64 linux.img -device virtio-net-pci,netdev=n1 \
        -netdev tap,id=n1,"helper=/usr/lib/qemu/qemu-bridge-helper"

bridge,id=id[,br=bridge][,helper=helper] — connects a host TAP network interface to a host bridge device. 🌉

It uses the network helper helper to configure the TAP interface and attach it to the bridge. The default network helper executable is /usr/lib/qemu/qemu-bridge-helper and the default bridge device is br0. ✨

Examples:

#launch a QEMU instance with the default network helper to
#connect a TAP device to bridge br0
qemu-system-x86_64 linux.img -netdev bridge,id=n1 -device virtio-net,netdev=n1

#launch a QEMU instance with the default network helper to
#connect a TAP device to bridge qemubr0
qemu-system-x86_64 linux.img -netdev bridge,br=qemubr0,id=n1 -device virtio-net,netdev=n1

socket,id=id[,fd=h][,listen=[host]:port][,connect=host:port] — this host network backend links the guest's network to another QEMU virtual machine over a TCP socket connection. If you pass listen, QEMU chills and waits for incoming connections on port (host is optional). Use connect to hook up to another QEMU instance that's using the listen option. And fd=h specifies an already-opened TCP socket. 🔥

Example:

# launch a first QEMU instance
qemu-system-x86_64 linux.img \
                 -device e1000,netdev=n1,mac=52:54:00:12:34:56 \
                 -netdev socket,id=n1,listen=:1234
# connect the network of this instance to the network of the first instance
qemu-system-x86_64 linux.img \
                 -device e1000,netdev=n2,mac=52:54:00:12:34:57 \
                 -netdev socket,id=n2,connect=127.0.0.1:1234

socket,id=id[,fd=h][,mcast=maddr:port[,localaddr=addr]] — configures a socket host network backend to share the guest's network traffic with other QEMU virtual machines using a UDP multicast socket — effectively building a bus for every QEMU sharing the same multicast address maddr and port. 💀 NOTES:
1. Several QEMUs can run on different hosts and share the same bus (assuming the multicast setup on those hosts is correct).
2. mcast support is compatible with User Mode Linux (argument ethN=mcast), see <http://user-mode-linux.sf.net>.
3. Use fd=h to specify an already-opened UDP multicast socket.

Example:

okay so bestie, here's how the multicast mcast thing actually looks in the wild — three whole QEMU instances vibing on the same "bus", all sharing one multicast address like a group chat 💬

# launch one QEMU instance
qemu-system-x86_64 linux.img \
                 -device e1000,netdev=n1,mac=52:54:00:12:34:56 \
                 -netdev socket,id=n1,mcast=230.0.0.1:1234
# launch another QEMU instance on same "bus"
qemu-system-x86_64 linux.img \
                 -device e1000,netdev=n2,mac=52:54:00:12:34:57 \
                 -netdev socket,id=n2,mcast=230.0.0.1:1234
# launch yet another QEMU instance on same "bus"
qemu-system-x86_64 linux.img \
                 -device e1000,netdev=n3,mac=52:54:00:12:34:58 \
                 -netdev socket,id=n3,mcast=230.0.0.1:1234

Example (User Mode Linux compat.):

# launch QEMU instance (note mcast address selected is UML's default)
qemu-system-x86_64 linux.img \
                 -device e1000,netdev=n1,mac=52:54:00:12:34:56 \
                 -netdev socket,id=n1,mcast=239.192.168.1:1102
# launch UML
/path/to/linux ubd0=/path/to/root_fs eth0=mcast

Example (send packets from host's 1.2.3.4):

qemu-system-x86_64 linux.img \
                 -device e1000,netdev=n1,mac=52:54:00:12:34:56 \
                 -netdev socket,id=n1,mcast=239.192.168.1:1102,localaddr=1.2.3.4

-netdev stream,id=str[,server=on|off],addr.type=inet,addr.host=host,addr.port=port[,to=maxport][,numeric=on|off][,keep-alive=on|off][,mptcp=on|off][,addr.ipv4=on|off][,addr.ipv6=on|off][,reconnect-ms=milliseconds] — set up a network backend that connects to another QEMU virtual machine (or a proxy, bestie, we don't judge) over a TCP/IP socket ✨
- server=on|off — if on, you're creating a server socket (so you're the host of the party 🎉)
- addr.host=host,addr.port=port — the socket address you listen on (when server=on) or connect to (when server=off)
- to=maxport — if present, this is range of possible addresses, with port between port and maxport.
- numeric=on|off — if on, host and port are guaranteed to be numeric; otherwise a name resolution should be attempted (default: off)
- keep-alive=on|off — enable keep-alive when connecting to this socket. Not supported for passive sockets.
- mptcp=on|off — enable multipath TCP (fancy, we love her 💅)
- ipv4=on|off — whether to accept IPv4 addresses, default to try both IPv4 and IPv6
- ipv6=on|off — whether to accept IPv6 addresses, default to try both IPv4 and IPv6
- reconnect-ms=milliseconds — for a client socket, if a socket is disconnected, then attempt a reconnect after the given number of milliseconds. Setting this to zero disables this function. (default: 0)

Example (two guests connected using a TCP/IP socket):

# first VM
qemu-system-x86_64 linux.img \
              -device virtio-net,netdev=net0,mac=52:54:00:12:34:56 \
              -netdev stream,id=net0,server=on,addr.type=inet,addr.host=localhost,addr.port=1234
# second VM
qemu-system-x86_64 linux.img \
              -device virtio-net,netdev=net0,mac=52:54:00:12:34:57 \
              -netdev stream,id=net0,server=off,addr.type=inet,addr.host=localhost,addr.port=1234,reconnect-ms=5000

-netdev stream,id=str[,server=on|off],addr.type=unix,addr.path=path[,abstract=on|off][,tight=on|off][,reconnect-ms=milliseconds] — set up a network backend that connects to another QEMU virtual machine or a proxy using a stream oriented unix domain socket 🦋
- server=on|off — if on create a server socket
- addr.path=path — filesystem path to use
- abstract=on|off — if on, this is a Linux abstract socket address.
- tight=on|off — if false, pad an abstract socket address with enough null bytes to make it fill struct sockaddr_un member sun_path.
- reconnect-ms=milliseconds — for a client socket, if a socket is disconnected, then attempt a reconnect after the given number of milliseconds. Setting this to zero disables this function. (default: 0)

Example (using passt as a replacement of -netdev user):

# start passt server as a non privileged user
passt
UNIX domain socket bound at /tmp/passt_1.socket
# start QEMU to connect to passt
qemu-system-x86_64 linux.img \
              -device virtio-net,netdev=net0 \
              -netdev stream,id=net0,server=off,addr.type=unix,addr.path=/tmp/passt_1.socket

Example (two guests connected using a stream oriented unix domain socket):

# first VM
qemu-system-x86_64 linux.img \
              -device virtio-net,netdev=net0,mac=52:54:00:12:34:56 \
              netdev stream,id=net0,server=on,addr.type=unix,addr.path=/tmp/qemu0
# second VM
qemu-system-x86_64 linux.img \
              -device virtio-net,netdev=net0,mac=52:54:00:12:34:57 \
              -netdev stream,id=net0,server=off,addr.type=unix,addr.path=/tmp/qemu0,reconnect-ms=5000

-netdev stream,id=str[,server=on|off],addr.type=fd,addr.str=file-descriptor[,reconnect-ms=milliseconds] — set up a network backend that connects to another QEMU virtual machine or a proxy using a stream oriented socket file descriptor 🍓
- server=on|off — if on create a server socket
- addr.str=file-descriptor — file descriptor number to use as a socket
- reconnect-ms=milliseconds — for a client socket, if a socket is disconnected, then attempt a reconnect after the given number of milliseconds. Setting this to zero disables this function. (default: 0)
-netdev dgram,id=str,remote.type=inet,remote.host=maddr,remote.port=port[,local.type=inet,local.host=addr] — set up a network backend that connects to a multicast address 📡
- remote.host=maddr,remote.port=port — multicast address
- local.host=addr — specify the host address to send packets from

Example:

# launch one QEMU instance
qemu-system-x86_64 linux.img \
              -device virtio-net,netdev=net0,mac=52:54:00:12:34:56 \
              -netdev dgram,id=net0,remote.type=inet,remote.host=224.0.0.1,remote.port=1234
# launch another QEMU instance on same "bus"
qemu-system-x86_64 linux.img \
              -device virtio-net,netdev=net0,mac=52:54:00:12:34:57 \
              -netdev dgram,id=net0,remote.type=inet,remote.host=224.0.0.1,remote.port=1234
# launch yet another QEMU instance on same "bus"
qemu-system-x86_64 linux.img \
              -device virtio-net,netdev=net0,mac=52:54:00:12:34:58 \
              -netdev dgram,id=net0,remote.type=inet,remote.host=224.0.0.1,remote.port=1234

-netdev dgram,id=str,remote.type=inet,remote.host=maddr,remote.port=port[,local.type=fd,local.str=file-descriptor] — set up a network backend that connects to a multicast address using a UDP socket file descriptor ✨
- remote.host=maddr,remote.port=port — multicast address
- local.str=file-descriptor — File descriptor to use to send packets
-netdev dgram,id=str,local.type=inet,local.host=addr,local.port=port[,remote.type=inet,remote.host=addr,remote.port=port] — set up a network backend to connect to another QEMU virtual machine or a proxy using a datagram oriented unix domain socket. (yes bestie it says unix domain socket, we're just relaying the lore, no cap 😭)
- local.host=addr,local.port=port — IP address to use to send the packets from
- remote.host=addr,remote.port=port — Destination IP address

Example (two guests connected using an UDP/IP socket):

# first VM
qemu-system-x86_64 linux.img \
              -device virtio-net,netdev=net0,mac=52:54:00:12:34:56 \
              -netdev dgram,id=net0,local.type=inet,local.host=localhost,local.port=1234,remote.type=inet,remote.host=localhost,remote.port=1235
# second VM
qemu-system-x86_64 linux.img \
              -device virtio-net,netdev=net0,mac=52:54:00:12:34:56 \
              -netdev dgram,id=net0,local.type=inet,local.host=localhost,local.port=1235,remote.type=inet,remote.host=localhost,remote.port=1234

-netdev dgram,id=str,local.type=unix,local.path=path[,remote.type=unix,remote.path=path] — set up a network backend to connect to another QEMU virtual machine or a proxy using a datagram oriented unix socket 🧚
- local.path=path — filesystem path to use to bind the socket
- remote.path=path — filesystem path to use as a destination (see sendto(2))

Example (two guests connected using an UDP/UNIX socket):

# first VM
qemu-system-x86_64 linux.img \
              -device virtio-net,netdev=net0,mac=52:54:00:12:34:56 \
              -netdev dgram,id=net0,local.type=unix,local.path=/tmp/qemu0,remote.type=unix,remote.path=/tmp/qemu1
# second VM
qemu-system-x86_64 linux.img \
              -device virtio-net,netdev=net0,mac=52:54:00:12:34:57 \
              -netdev dgram,id=net0,local.type=unix,local.path=/tmp/qemu1,remote.type=unix,remote.path=/tmp/qemu0

-netdev dgram,id=str,local.type=fd,local.str=file-descriptor — set up a network backend to connect to another QEMU virtual machine or a proxy using a datagram oriented socket file descriptor 💚
- local.str=file-descriptor — File descriptor to use to send packets
-netdev l2tpv3,id=id,src=srcaddr,dst=dstaddr[,srcport=srcport][,dstport=dstport],txsession=txsession[,rxsession=rxsession][,ipv6=on|off][,udp=on|off][,cookie64=on|off][,counter=on|off][,pincounter=on|off][,txcookie=txcookie][,rxcookie=rxcookie][,offset=offset] — set up an L2TPv3 pseudowire host network backend. L2TPv3 (RFC3931) is a popular protocol to transport Ethernet (and other Layer 2) data frames between two systems. It is present in routers, firewalls and the Linux kernel (from version 3.3 onwards). 👑

This transport lets a VM talk directly to another VM, a router, or a firewall. Directly directly. No middleman. 💅

src=srcaddr — where you're coming from. Mandatory, bestie, you can't skip it.
dst=dstaddr — where you're headed. Also mandatory. Periodt.
udp=on — flip on udp encapsulation (the default is ip, jsyk).
srcport=srcport — the source udp port.
dstport=dstport — the destination udp port.
ipv6=on — force v6. Otherwise it just defaults to v4, no drama.
rxcookie=rxcookie; txcookie=txcookie — cookies are a weak form of security in the l2tpv3 spec. Their whole job is basically stopping you from misconfiguring stuff. Default is 32 bit.
cookie64=on — make the cookie 64 bit instead of the default 32.
counter=off — forces a 'cut-down' L2TPv3 with no counter, exactly like draft-mkonstan-l2tpext-keyed-ipv6-tunnel-00.
pincounter=on — works around broken counter handling in the peer. Also lowkey helps on networks with packet reorder.
offset=offset — adds an extra offset between header and data.

Okay so say you wanna attach a VM running on host 4.3.2.1 via L2TPv3 to the bridge br-lan on the remote Linux host 1.2.3.4. Iconic. Here's the whole thing:

# Setup tunnel on linux host using raw ip as encapsulation
# on 1.2.3.4
ip l2tp add tunnel remote 4.3.2.1 local 1.2.3.4 tunnel_id 1 peer_tunnel_id 1 \
    encap udp udp_sport 16384 udp_dport 16384
ip l2tp add session tunnel_id 1 name vmtunnel0 session_id \
    0xFFFFFFFF peer_session_id 0xFFFFFFFF
ifconfig vmtunnel0 mtu 1500
ifconfig vmtunnel0 up
brctl addif br-lan vmtunnel0

# on 4.3.2.1
# launch QEMU instance - if your network has reorder or is very lossy add ,pincounter

qemu-system-x86_64 linux.img -device e1000,netdev=n1 \
    -netdev l2tpv3,id=n1,src=4.2.3.1,dst=1.2.3.4,udp=on,srcport=16384,dstport=16384,rxsession=0xffffffff,txsession=0xffffffff,counter=on

-netdev vde

vde,id=id[,sock=socketpath][,port=n][,group=groupname][,mode=octalmode]

Set up a VDE backend to connect to PORT n of a vde switch that's running on the host and listening for incoming connections on socketpath. Wanna change the default ownership and permissions for the communication port? Use GROUP groupname and MODE octalmode. 🫶

Heads up: this option is only available if QEMU was compiled with vde support enabled. No vde build, no vde vibes.

Example, because examples are the moment:

# launch vde switch
vde_switch -F -sock /tmp/myswitch
# launch QEMU instance
qemu-system-x86_64 linux.img -nic vde,sock=/tmp/myswitch

-netdev af-xdp

af-xdp,id=str,ifname=name[,mode=native|skb][,force-copy=on|off][,queues=n][,start-queue=m][,inhibit=on|off][,sock-fds=x:y:...:z][,map-path=/path/to/socket/map][,map-start-index=i]

This one configures the AF_XDP backend to connect to a network interface 'name' using an AF_XDP socket. You can force a specific program attach mode for a default XDP program with 'mode'; it defaults to best-effort, where the likely most performant mode gets used. Number of queues 'n' should generally match the number of queues in the interface — defaults to 1. And traffic arriving on non-configured device queues will not be delivered to the network backend. So like, be aware.

# set number of queues to 4
ethtool -L eth0 combined 4
# launch QEMU instance
qemu-system-x86_64 linux.img -device virtio-net-pci,netdev=n1 \
    -netdev af-xdp,id=n1,ifname=eth0,queues=4

The 'start-queue' option can be specified if a particular range of queues [m, m + n] should be in use. For example, this may be necessary to use certain NICs in native mode. The kernel lets the driver create a separate set of XDP queues on top of the regular ones, and only these queues can be used for AF_XDP sockets. NICs that work this way may also need an additional traffic redirection with ethtool to those special queues.

# set number of queues to 1
ethtool -L eth0 combined 1
# redirect all the traffic to the second queue (id: 1)
# note: drivers may require non-empty key/mask pair.
ethtool -N eth0 flow-type ether \
    dst 00:00:00:00:00:00 m FF:FF:FF:FF:FF:FE action 1
ethtool -N eth0 flow-type ether \
    dst 00:00:00:00:00:01 m FF:FF:FF:FF:FF:FE action 1
# launch QEMU instance
qemu-system-x86_64 linux.img -device virtio-net-pci,netdev=n1 \
    -netdev af-xdp,id=n1,ifname=eth0,queues=1,start-queue=1

The XDP program can also be loaded externally. In that case the 'inhibit' option should be set to 'on'. Either 'sock-fds' or 'map-path' can be used with 'inhibit' enabled. 'sock-fds' can be provided with file descriptors for already open but not bound XDP sockets that were already added to a socket map for the corresponding queues. One socket per queue.

qemu-system-x86_64 linux.img -device virtio-net-pci,netdev=n1 \
    -netdev af-xdp,id=n1,ifname=eth0,queues=3,inhibit=on,sock-fds=15:16:17

When the 'inhibit' option is set to 'on' and used together with 'map-path', it's expected that the XDP program with the socket map is already loaded on the networking device and that the map is pinned into the BPF file system. The path to the pinned map then gets passed to QEMU, which creates the file descriptors and inserts them into the existing socket map. Chef's kiss. 👑

qemu-system-x86_64 linux.img -device virtio-net-pci,netdev=n1 \
    -netdev af-xdp,id=n1,ifname=eth0,queues=2,inhibit=on,map-path=/sys/fs/bpf/xsks_map

Also, 'map-start-index' can be used to specify the start offset for insertion into the socket map.

And the combination of 'map-path' and 'sock-fds' together is not supported. Pick one, bestie. 🙈

-netdev vhost-user

-netdev vhost-user,chardev=id[,vhostforce=on|off][,queues=n]

Establish a vhost-user netdev, backed by a chardev id. That chardev should be a unix domain socket backed one. The vhost-user uses a specifically defined protocol to pass vhost ioctl replacement messages to an application on the other end of the socket. On non-MSIX guests, the feature can be forced with vhostforce. And use 'queues=n' to specify the number of queues to be created for multiqueue vhost-user.

Example:

qemu -m 512 -object memory-backend-file,id=mem,size=512M,mem-path=/hugetlbfs,share=on \
     -numa node,memdev=mem \
     -chardev socket,id=chr0,path=/path/to/socket \
     -netdev type=vhost-user,id=net0,chardev=chr0 \
     -device virtio-net-pci,netdev=net0

-netdev vhost-vdpa

-netdev vhost-vdpa[,vhostdev=/path/to/dev][,vhostfd=h]

Establish a vhost-vdpa netdev.

A vDPA device is a device that uses a datapath which complies with the virtio specifications with a vendor specific control path. vDPA devices can be both physically located on the hardware or emulated by software. The range, honestly. 💜

-netdev hubport

-netdev hubport,id=id,hubid=hubid[,netdev=nd]

Create a hub port on the emulated hub with ID hubid.

The hubport netdev lets you connect a NIC to a QEMU emulated hub instead of a single netdev. Or, alternatively, you can also connect the hubport to another netdev with ID nd by using the netdev=nd option. Two options, both slay.

-net nic

-net nic[,netdev=nd][,macaddr=mac][,model=type]
[,name=name][,addr=addr][,vectors=v]

The legacy option to configure or create an on-board (or machine default) Network Interface Card (NIC) and connect it either to the emulated hub with ID 0 (aka the default hub), or to the netdev nd. If model is omitted, then the default NIC model associated with the machine type is used.

Note: the default NIC model may change in future QEMU releases, so it is highly recommended to always specify a model. Like, always. No cap.

Optionally, the MAC address can be changed to mac, the device address set to addr (PCI cards only), and a name can be assigned for use in monitor commands. Also optionally, for PCI cards, you can specify the number v of MSI-X vectors that the card should have — this option currently only affects virtio cards; set v = 0 to disable MSI-X. If no -net option is specified, a single NIC is created. QEMU can emulate several different models of network card. Use -net nic,model=help for a list of available devices for your target. 💖

-net user|passt|tap|bridge|socket|l2tpv3|vde

-net user|passt|tap|bridge|socket|l2tpv3|vde[,...][,name=name]

Configure a host network backend (with the options corresponding to the same -netdev option) and connect it to the emulated hub 0 (the default hub). Use name to specify the name of the hub port.

🎀 Character device options 🎀

The general form of a character device option is:

-chardev backend,id=id[,mux=on|off][,options]

Backend is one of: null, socket, udp, msmouse, hub, vc, ringbuf, file, pipe, console, serial, pty, stdio, braille, parallel, spicevmc, spiceport. The specific backend will determine the applicable options.

Use -chardev help to print all available chardev backend types. ✨

All devices must have an id, which can be any string up to 127 characters long. It's used to uniquely identify this device in other command line directives.

A character device may be used in multiplexing mode by multiple front-ends. Specify mux=on to enable this mode. A multiplexer is a "1:N" device, and here the "1" end is your specified chardev backend, and the "N" end is the various parts of QEMU that can talk to a chardev. If you create a chardev with id=myid and mux=on, QEMU will create a multiplexer with your specified ID, and you can then configure multiple front ends to use that chardev ID for their input/output. Up to four different front ends can be connected to a single multiplexed chardev. (Without multiplexing enabled, a chardev can only be used by a single front end.) For instance you could use this to allow a single stdio chardev to be used by two serial ports and the QEMU monitor:

-chardev stdio,mux=on,id=char0 \
-mon chardev=char0,mode=readline \
-serial chardev:char0 \
-serial chardev:char0

Okay so you can absolutely have more than one multiplexer in a system configuration, bestie — like fr, you could have a TCP port multiplexed between UART 0 and UART 1, and stdio multiplexed between the QEMU monitor and a parallel port:

 -chardev stdio,mux=on,id=char0 \
 -mon chardev=char0,mode=readline \
 -parallel chardev:char0 \
 -chardev tcp,...,mux=on,id=char1 \
 -serial chardev:char1 \
 -serial chardev:char1

When you're using a multiplexed character device, some escape sequences get interpreted in the input. See the chapter about Keys in the character backend multiplexer <#keys-in-the-character-backend-multiplexer> in the System Emulation Users Guide for more details. 🧚

Also heads up: some other command line options may implicitly create multiplexed character backends. Like, -serial mon:stdio creates a multiplexed stdio backend connected to the serial port and the QEMU monitor, and -nographic also multiplexes the console and the monitor to stdio. Sneaky little icons. 💅

If you need to aggregate data in the opposite direction (where one QEMU frontend interface receives input and output from multiple backend chardev devices), please refer to the paragraph below regarding chardev hub aggregator device configuration.

Every backend supports the logfile option, which supplies the path to a file to record all data transmitted via the backend. The logappend option controls whether the log file will be truncated or appended to when opened.

The available backends are:

🕳️ `-chardev null,id=id`

A literal void device. This one will not emit any data, and will drop any data it receives. The null backend does not take any options. It's giving "I'm just here for the vibes and also I eat everything you give me." 💀

🧦 `-chardev socket,id=id[,TCP options or unix options][,server=on|off][,wait=on|off][,telnet=on|off][,websocket=on|off][,reconnect-ms=milliseconds][,tls-creds=id][,tls-authz=id]`

Create a two-way stream socket, which can be either a TCP or a unix socket. A unix socket will be created if path is specified.

Behaviour is undefined if TCP options are specified for a unix socket. Not "undefined" like cute-undefined, like actually don't. 🙈

server=on|off specifies that the socket shall be a listening socket.

wait=on|off specifies that QEMU should not block waiting for a client to connect to a listening socket.

telnet=on|off specifies that traffic on the socket should interpret telnet escape sequences.

websocket=on|off specifies that the socket uses WebSocket protocol for communication.

reconnect-ms sets the timeout for reconnecting on non-server sockets when the remote end goes away. qemu will delay this many milliseconds and then attempt to reconnect. Zero disables reconnecting, and is the default.

tls-creds requests enablement of the TLS protocol for encryption, and specifies the id of the TLS credentials to use for the handshake. The credentials must be previously created with the -object tls-creds argument.

tls-auth provides the ID of the QAuthZ authorization object against which the client's x509 distinguished name will be validated. This object is only resolved at time of use, so can be deleted and recreated on the fly while the chardev server is active. If missing, it will default to denying access. Deny by default, periodt.

TCP and unix socket options are given below:

🐟 TCP options

port=port[,host=host][,to=to][,ipv4=on|off][,ipv6=on|off][,nodelay=on|off]

host for a listening socket specifies the local address to be bound. For a connecting socket species the remote host to connect to. host is optional for listening sockets. If not specified it defaults to 0.0.0.0.
port for a listening socket specifies the local port to be bound. For a connecting socket specifies the port on the remote host to connect to. port can be given as either a port number or a service name. port is required.
to is only relevant to listening sockets. If it is specified, and port cannot be bound, QEMU will attempt to bind to subsequent ports up to and including to until it succeeds. to must be specified as a port number.
ipv4=on|off and ipv6=on|off specify that either IPv4 or IPv6 must be used. If neither is specified the socket may use either protocol.
nodelay=on|off disables the Nagle algorithm.

🐚 unix options

path=path[,abstract=on|off][,tight=on|off]

path specifies the local path of the unix socket. path is required.
abstract=on|off specifies the use of the abstract socket namespace, rather than the filesystem. Optional, defaults to false.
tight=on|off sets the socket length of abstract sockets to their minimum, rather than the full sun_path length. Optional, defaults to true.

📡 `-chardev udp,id=id[,host=host],port=port[,localaddr=localaddr][,localport=localport][,ipv4=on|off][,ipv6=on|off]`

Sends all traffic from the guest to a remote host over UDP. Classic "fire and forget" energy, honestly.

host specifies the remote host to connect to. If not specified it defaults to localhost.
port specifies the port on the remote host to connect to. port is required.
localaddr specifies the local address to bind to. If not specified it defaults to 0.0.0.0.
localport specifies the local port to bind to. If not specified any available local port will be used.
ipv4=on|off and ipv6=on|off specify that either IPv4 or IPv6 must be used. If neither is specified the device may use either protocol.

🐭 `-chardev msmouse,id=id`

Forward QEMU's emulated msmouse events to the guest. msmouse does not take any options. Just a little mouse guy, no config, no notes. 🐁

🛞 `-chardev hub,id=id,chardevs.0=id[,chardevs.N=id]`

Explicitly create chardev backend hub device with the possibility to aggregate input from multiple backend devices and forward it to a single frontend device. Additionally, hub device takes the output from the frontend device and sends it back to all the connected backend devices. This allows for seamless interaction between different backend devices and a single frontend interface. Aggregation supported for up to 4 chardev devices. (Since 10.0)

For example, the following is a use case of 2 backend devices: virtual console vc0 and a pseudo TTY pty0 connected to a single virtio hvc console frontend device with a hub hub0 help. Virtual console renders text to an image, which can be shared over the VNC protocol. In turn, pty backend provides bidirectional communication to the virtio hvc console over the pseudo TTY file. The example configuration can be as follows:

 -chardev pty,path=/tmp/pty,id=pty0 \
 -chardev vc,id=vc0 \
 -chardev hub,id=hub0,chardevs.0=pty0,chardevs.1=vc0 \
 -device virtconsole,chardev=hub0 \
 -vnc 0.0.0.0:0

Once QEMU starts VNC client and any TTY emulator can be used to control a single hvc console:

 # Start TTY emulator
 tio /tmp/pty

 # Start VNC client and switch to virtual console Ctrl-Alt-2
 vncviewer :0

Several frontend devices is not supported. Stacking of multiplexers and hub devices is not supported as well. So no hub-ception, sorry bestie. 😭

🖥️ `-chardev vc,id=id[[,width=width][,height=height]][[,cols=cols][,rows=rows]]`

Connect to a QEMU text console. vc may optionally be given a specific size.

width and height specify the width and height respectively of the console, in pixels.
cols and rows specify that the console be sized to fit a text console with the given dimensions.

💍 `-chardev ringbuf,id=id[,size=size]`

Create a ring buffer with fixed size size. size must be a power of two and defaults to 64K. Powers of two only, it's giving "we have rules here." ✨

📄 `-chardev file,id=id,path=path[,input-path=input-path]`

Log all traffic received from the guest to a file.

path specifies the path of the file to be opened. This file will be created if it does not already exist, and overwritten if it does. path is required.
If input-path is specified, this is the path of a second file which will be used for input. If input-path is not specified, no input will be available from the chardev.

Note that input-path is not supported on Windows hosts.

🚰 `-chardev pipe,id=id,path=path`

Create a two-way connection to the guest. The behaviour differs slightly between Windows hosts and other hosts:

On Windows, a single duplex pipe will be created at \\.pipe\path.
On other hosts, 2 pipes will be created called path.in and path.out. Data written to path.in will be received by the guest. Data written by the guest can be read from path.out. QEMU will not create these fifos, and requires them to be present.

path forms part of the pipe path as described above. path is required.

🪟 `-chardev console,id=id`

Send traffic from the guest to QEMU's standard output. console does not take any options.

console is only available on Windows hosts.

🔌 `-chardev serial,id=id,path=path`

Send traffic from the guest to a serial device on the host.

On Unix hosts serial will actually accept any tty device, not only serial lines. Lowkey flexible of it.

path specifies the name of the serial device to open.

🎀 `-chardev pty,id=id[,path=path]`

Create a new pseudo-terminal on the host and connect to it.

pty is not available on Windows hosts.

If path is specified, QEMU will create a symbolic link at that location which points to the new PTY device.

This avoids having to make QMP or HMP monitor queries to find out what the new PTY device path is. Convenient, iconic, no notes. 💅

Note that while QEMU will remove the symlink when it exits gracefully, it will not do so in case of crashes or on certain startup errors. It is recommended that the user checks and removes the symlink after QEMU terminates to account for this. So like, do a little cleanup sweep, bestie. 🧹

🫶 `-chardev stdio,id=id[,signal=on|off]`

Connect to standard input and standard output of the QEMU process.

okay so signal controls whether signals are enabled on the terminal, and bestie that includes exiting QEMU with the key sequence Control-c. 💅 This option is enabled by default — use signal=off to disable it. periodt.

-chardev braille,id=id — connects you to a local BrlAPI server. 🦋 braille takes no options at all, it's that low-maintenance.
-chardev parallel,id=id,path=path — connect to a local parallel port.

parallel is only available on Linux, FreeBSD and DragonFlyBSD hosts. no cap.

path specifies the path to the parallel port device. path is required. 🙈

-chardev spicevmc,id=id,debug=debug,name=name — spicevmc is only available when spice support is built in, fyi.
- debug — debug level for spicevmc
- name — name of the spice channel to connect to

Connect to a spice virtual machine channel, such as vdiport. ✨

-chardev spiceport,id=id,debug=debug,name=name — spiceport is also only available when spice support is built in.
- debug — debug level for spicevmc
- name — name of the spice port to connect to

Connect to a spice port, which lets a Spice client handle the traffic identified by a name (preferably a fqdn). 👑

🎀 TPM device options 🎀

The general form of a TPM device option is:

-tpmdev backend,id=id[,options]

The specific backend type will determine the applicable options. The -tpmdev option creates the TPM backend, and it requires a -device option that specifies the TPM frontend interface model. 🫶

Use -tpmdev help to print all available TPM backend types.

The available backends are:

-tpmdev passthrough,id=id,path=path,cancel-path=cancel-path — (Linux-host only) enable access to the host's TPM using the passthrough driver.
- path — specifies the path to the host's TPM device, i.e., on a Linux host this would be /dev/tpm0. path is optional and by default /dev/tpm0 is used.
- cancel-path — specifies the path to the host TPM device's sysfs entry allowing for cancellation of an ongoing TPM command. cancel-path is optional and by default QEMU will search for the sysfs entry to use.

Some notes about using the host's TPM with the passthrough driver: 💀

The TPM device accessed by the passthrough driver must not be used by any other application on the host.
Since the host's firmware (BIOS/UEFI) has already initialized the TPM, the VM's firmware (BIOS/UEFI) will not be able to initialize the TPM again and may therefore not show a TPM-specific menu that would otherwise allow the user to configure the TPM, e.g., allow the user to enable/disable or activate/deactivate the TPM. Further, if TPM ownership is released from within a VM then the host's TPM will get disabled and deactivated. To enable and activate the TPM again afterwards, the host has to be rebooted and the user is required to enter the firmware's menu to enable and activate the TPM. If the TPM is left disabled and/or deactivated most TPM commands will fail.

To create a passthrough TPM use the following two options:

-tpmdev passthrough,id=tpm0 -device tpm-tis,tpmdev=tpm0

Note that the -tpmdev id is tpm0 and is referenced by tpmdev=tpm0 in the device option.

-tpmdev emulator,id=id,chardev=dev — (Linux-host only) enable access to a TPM emulator using Unix domain socket based chardev backend.

chardev specifies the unique ID of a character device backend that provides connection to the software TPM server.

To create a TPM emulator backend device with chardev socket backend:

-chardev socket,id=chrtpm,path=/tmp/swtpm-sock -tpmdev emulator,id=tpm0,chardev=chrtpm -device tpm-tis,tpmdev=tpm0

🌈 Boot Image or Kernel specific 🌈

There are broadly 4 ways you can boot a system with QEMU:

specify a firmware and let it control finding a kernel
specify a firmware and pass a hint to the kernel to boot
direct kernel image boot
manually load files into the guest's address space

The third method is useful for quickly testing kernels but as there is no firmware to pass configuration information to the kernel the hardware must either be probeable, the kernel built for the exact configuration or passed some configuration data (e.g. a DTB blob) which tells the kernel what drivers it needs. This exact details are often hardware specific.

The final method is the most generic way of loading images into the guest address space and used mostly for bare metal type development where the reset vectors of the processor are taken into account.

For x86 machines and some other architectures -bios will generally do the right thing with whatever it is given. For other machines the more strict -pflash option needs an image that is sized for the flash device for the given machine type.

Please see the QEMU System Emulator Targets <#system-targets-ref> section of the manual for more detailed documentation.

-bios file — set the filename for the BIOS.
-pflash file — use file as a parallel flash image.

The kernel options were designed to work with Linux kernels although other things (like hypervisors) can be packaged up as a kernel executable image. The exact format of a executable image is usually architecture specific.

The way in which the kernel is started (what address it is loaded at, what if any information is passed to it via CPU registers, the state of the hardware when it is started, and so on) is also architecture specific. Typically it follows the specification laid down by the Linux kernel for how kernels for that architecture must be started.

-kernel bzImage — use bzImage as kernel image. The kernel can be either a Linux kernel or in multiboot format.
-shim shim.efi — use shim.efi to boot the kernel
-append cmdline — use cmdline as kernel command line
-initrd file — use file as initial ram disk.
-initrd "file1 arg=foo,file2" — this syntax is only available with multiboot. Use file1 and file2 as modules and pass arg=foo as parameter to the first module. Commas can be provided in module parameters by doubling them on the command line to escape them:
-initrd "bzImage earlyprintk=xen,,keep root=/dev/xvda1,initrd.img" — Multiboot only. Use bzImage as the first module with earlyprintk=xen,keep root=/dev/xvda1 as its command line, and initrd.img as the second module.
-dtb file — use file as a device tree binary (dtb) image and pass it to the kernel on boot.

Finally you can also manually load images directly into the address space of the guest. This is most useful for developers who already know the layout of their guest and take care to ensure something sane will happen when the reset vector executes.

The generic loader can be invoked by using the loader device:

-device loader,addr=<addr>,data=<data>,data-len=<data-len>[,data-be=<data-be>][,cpu-num=<cpu-num>]

there is also the guest loader which operates in a similar way but tweaks the DTB so a hypervisor loaded via -kernel can find where the guest image is:

-device guest-loader,addr=<addr>[,kernel=<path>,[bootargs=<arguments>]][,initrd=<path>]

💅 Debug/Expert options 💅

-compat [deprecated-input=@var{input-policy}][,deprecated-output=@var{output-policy}] — set policy for handling deprecated management interfaces (experimental):
- deprecated-input=accept (default) — accept deprecated commands and arguments
- deprecated-input=reject — reject deprecated commands and arguments
- deprecated-input=crash — crash on deprecated commands and arguments
- deprecated-output=accept (default) — emit deprecated command results and events
- deprecated-output=hide — suppress deprecated command results and events

Limitation: covers only syntactic aspects of QMP.

-compat [unstable-input=@var{input-policy}][,unstable-output=@var{output-policy}] — set policy for handling unstable management interfaces (experimental):
- unstable-input=accept (default) — accept unstable commands and arguments
- unstable-input=reject — reject unstable commands and arguments
- unstable-input=crash — crash on unstable commands and arguments
- unstable-output=accept (default) — emit unstable command results and events
- unstable-output=hide — suppress unstable command results and events

Limitation: covers only syntactic aspects of QMP.

-fw_cfg [name=]name,file=file — add named fw_cfg entry with contents from file file. If the filename contains comma, you must double it (for instance, "file=my,,file" to use file "my,file").
-fw_cfg [name=]name,string=str — add named fw_cfg entry with contents from string str. If the string contains comma, you must double it (for instance, "string=my,,string" to use file "my,string").

The terminating NUL character of the contents of str will not be included as part of the fw_cfg item data. To insert contents with embedded NUL characters, you have to use the file parameter.

The fw_cfg entries are passed by QEMU through to the guest.

Example:

-fw_cfg name=opt/com.mycompany/blob,file=./my_blob.bin

creates an fw_cfg entry named opt/com.mycompany/blob with contents from ./my_blob.bin.

-serial dev — redirect the virtual serial port to host character device dev. The default device is vc in graphical mode and stdio in non graphical mode. 🎀

This option can be used several times to simulate multiple serial ports.

You can use -serial none to suppress the creation of default serial devices.

Available character devices are:

vc[:WxH] — Virtual console. Optionally, a width and height can be given in pixel with

vc:800x600

It is also possible to specify width or height in characters:

vc:80Cx24C

pty[:path] — [Linux only] Pseudo TTY (a new PTY is automatically allocated).

If path is specified, QEMU will create a symbolic link at that location which points to the new PTY device.

This avoids having to make QMP or HMP monitor queries to find out what the new PTY device path is.

okay so real talk bestie 💖 QEMU will clean up that symlink when it exits gracefully — but it will not do it if it crashes, or on certain startup errors. So pls do the responsible thing: after QEMU terminates, check the symlink and remove it yourself, okay? it's giving "trust but verify" ✨

none — literally no device gets allocated. 🚫 Heads up though: on machine types that emulate systems where a serial device is always present in real hardware, this can end up being the same as the null option — the serial device is still there, but all its output gets yeeted into the void. For boards where the number of serial ports is genuinely variable, this actually suppresses creating the device at all.
null — the guest sees the UART / serial device as present in the machine 👀 but all output is discarded and there's no input. Conceptually it's the same energy as redirecting output to /dev/null.
chardev:id — use a named character device that you defined with the -chardev option.
/dev/XXX — [Linux only 🐧] use a host tty, e.g. /dev/ttyS0. The host serial port parameters get set according to the emulated ones.
/dev/parportN — [Linux only, parallel port only 🐧] use host parallel port N. Right now the SPP and EPP parallel port features can be used.
file:filename — write output to filename. No character can be read. 📝
stdio — [Unix only] standard input/output.
pipe:filename — name pipe filename.
COMn — [Windows only 🪟] use host serial port n.
udp:[remote_host]:remote_port[@[src_ip]:src_port] — this one implements UDP Net Console 📡. When remote_host or src_ip aren't specified they default to 0.0.0.0. And if you don't set a src_port, a random port is automatically chosen.

If you just want a simple readonly console, you can use netcat or nc — start QEMU with -serial udp::4555 and nc like nc -u -l -p 4555. Any time QEMU writes something to that port it'll show up in the netconsole session. 💅

If you plan to send characters back via netconsole, or you're gonna stop and start QEMU a whole bunch of times, you should have QEMU use the same source port every time, by doing something like -serial udp::4555@:4556. Another approach is a patched version of netcat that can listen on a TCP port and send/receive characters via udp. If you've got a patched netcat that activates telnet remote echo and single char transfer, then you can use the following options to set up a netcat redirector so telnet on port 5555 can reach the QEMU port.

QEMU Options:

-serial udp::4555@:4556

netcat options:

-u -P 4555 -L 0.0.0.0:4556 -t -p 5555 -I -T

telnet options:

localhost 5555

tcp:[host]:port[,server=on|off][,wait=on|off][,nodelay=on|off][,reconnect-ms=milliseconds] — the TCP Net Console has two modes of operation, bestie 🔀. It can send the serial I/O to a location, or wait for a connection from a location. By default the TCP Net Console is sent to host at the port. If you use the server=on option, QEMU will wait for a client socket application to connect to the port before continuing — unless the wait=on|off option was specified. The nodelay=on|off option disables the Nagle buffering algorithm. The reconnect-ms option only applies if server=no is set; if the connection goes down it'll attempt to reconnect at the given interval. If host is omitted, 0.0.0.0 is assumed. Only one TCP connection at a time is accepted. And you can use telnet=on to connect to the corresponding character device.

Example to send tcp console to 192.168.0.2 port 4444

-serial <tcp:192.168.0.2:4444>

Example to listen and wait on port 4444 for connection

-serial <tcp::4444,server=on>

Example to not wait and listen on ip 192.168.0.100 port 4444

-serial <tcp:192.168.0.100:4444,server=on,wait=off>

telnet:host:port[,server=on|off][,wait=on|off][,nodelay=on|off] — the telnet protocol gets used instead of raw tcp sockets 🧚. The options work exactly the same as if you'd specified -serial tcp. The difference? The port acts like a telnet server or client, using telnet option negotiation. This also lets you send the MAGIC_SYSRQ sequence, if you're using a telnet that supports sending the break sequence. Typically in unix telnet you do it with Control-] and then type "send break" followed by pressing the enter key.
websocket:host:port,server=on[,wait=on|off][,nodelay=on|off] — the WebSocket protocol gets used instead of a raw tcp socket 🌐. The port acts as a WebSocket server. Client mode is not supported.
unix:path[,server=on|off][,wait=on|off][,reconnect-ms=milliseconds] — a unix domain socket is used instead of a tcp socket 🔌. The option works the same as if you'd specified -serial tcp, except the unix domain socket path is used for connections.
mon:dev_string — this is a special option that lets the monitor be multiplexed onto another serial port 👑. You access the monitor with the key sequence Control-a and then pressing c. dev_string should be any one of the serial devices listed above. An example of multiplexing the monitor onto a telnet server listening on port 4444 would be:

-serial mon:telnet::4444,server=on,wait=off

And when the monitor is multiplexed to stdio this way, Ctrl+C will not terminate QEMU anymore — instead it gets passed to the guest. 😭

braille — Braille device. This uses BrlAPI to display the braille output on a real or fake device. 🫶
msmouse — three button serial mouse. Configure the guest to use the Microsoft protocol. 🖱️
-parallel dev — redirect the virtual parallel port to host device dev (same devices as the serial port, bestie). On Linux hosts, /dev/parportN can be used to use hardware devices connected on the corresponding host parallel port. 🐧

This option can be used several times to simulate up to 3 parallel ports.

Use -parallel none to disable all parallel ports.

-monitor dev — redirect the monitor to host device dev (again, same devices as the serial port). The default device is vc in graphical mode and stdio in non graphical mode. Use -monitor none to disable the default monitor. 👀
-qmp dev — like -monitor but it opens in 'control' mode 🎛️. For example, to make QMP available on localhost port 4444:

-qmp tcp:localhost:4444,server=on,wait=off

Not all options are configurable via this syntax — for maximum flexibility use the -mon option and an accompanying -chardev.

-qmp-pretty dev — like -qmp but it uses pretty JSON formatting ✨.
-mon [chardev=]name[,mode=readline|control][,pretty[=on|off]] — set up a monitor connected to the chardev name. QEMU supports two monitors: the Human Monitor Protocol (HMP, for human interaction 💬) and the QEMU Monitor Protocol (QMP, a JSON RPC-style protocol 🤖). The default is HMP; mode=control selects QMP instead. pretty is only valid when mode=control, and it turns on JSON pretty printing to make human reading and debugging easier.

For example:

-chardev socket,id=mon1,host=localhost,port=4444,server=on,wait=off \
-mon chardev=mon1,mode=control,pretty=on

...enables the QMP monitor on localhost port 4444 with pretty-printing. slay 💅

-debugcon dev — redirect the debug console to host device dev (you guessed it: same devices as the serial port). The debug console is an I/O port which is typically port 0xe9; writing to that I/O port sends output to this device. The default device is vc in graphical mode and stdio in non graphical mode. 🐛
-pidfile file — store the QEMU process PID in file. Super useful if you launch QEMU from a script. 📌
--preconfig — pause QEMU for interactive configuration before the machine is created, which lets you query and configure properties that will affect machine initialization ⏸️. Use the QMP command 'x-exit-preconfig' to exit the preconfig state and move to the next state (i.e. run guest if -S isn't used, or pause the second time if -S is used). This option is experimental. 🧪
-S — do not start the CPU at startup (you must type 'c' in the monitor). 😴
-overcommit mem-lock=on|off|on-fault
-overcommit cpu-pm=on|off — run qemu with hints about host resource overcommit. The default is to assume that the host overcommits all resources.

Locking qemu and guest memory can be enabled via mem-lock=on or mem-lock=on-fault (disabled by default). This works when host memory is not overcommitted, and it reduces the worst-case latency for the guest. The on-fault option is better for reducing the memory footprint since it makes allocations lazy — but the pages still get locked in place once faulted by the guest or QEMU. Note that the two options are mutually exclusive. ⚠️

The guest's ability to manage the power state of host cpus (which increases latency for other processes on the same host cpu, but decreases latency for the guest) can be enabled via cpu-pm=on (disabled by default). This works best when the host CPU is not overcommitted. When it's used, host estimates of CPU cycle and power utilization will be incorrect, because they don't take guest idle time into account. 💀

-gdb dev — bestie, this one lets gdb connect to QEMU on device dev (peep the GDB usage <#gdb-usage> chapter in the System Emulation Users Guide for the full lore). Heads up tho: this does not pause QEMU's execution. If you want QEMU to hold off starting the guest until you've connected with gdb and hit continue, you gotta ALSO pass the -S option. Two options, one vibe. 💅

The most usual setup is just listening on a local TCP socket, like:

-gdb tcp::3117

but fr fr you can use other backends too — UDP, pseudo TTY, even stdio are all totally reasonable use cases. A stdio connection lets you start QEMU from inside gdb and make the connection through a pipe, like this:

(gdb) target remote | exec qemu-system-x86_64 -gdb stdio ...

-s — shorthand for -gdb tcp::1234, i.e. it opens a gdbserver on TCP port 1234 (again, see the GDB usage <#gdb-usage> chapter in the System Emulation Users Guide). ✨
-d item1[,...] — turns on logging for the items you list. Run -d help and it'll hand you the full menu of log items. 👑
-D logfile — sends the log to logfile instead of to stderr. 📝
-dfilter range1[,...] — filters the debug output down to only what's relevant to a range of target addresses. The filter spec can be start+size, start-size or start..end, where start, end and size are the addresses and sizes you need. Like, for example:

-dfilter 0x8000..0x8fff,0xffffffc000080000+0x200,0xffffffc000060000-0x1000

That'll dump output for any code in the 0x1000-sized block starting at 0x8000, plus the 0x200-sized block starting at 0xffffffc000080000, plus another 0x1000-sized block starting at 0xffffffc00005f000. Math queen behavior honestly. 🧮

-seed number — forces the guest to use a deterministic pseudo-random number generator, seeded with number. Important tho: this does not affect crypto routines within the host. Different thing entirely, okurrr.
-L path — sets the directory for the BIOS, VGA BIOS and keymaps. 🗂️

Wanna see all the data directories? Just run -L help.

-enable-kvm — enables KVM full virtualization support. Only available if KVM support was enabled when compiling, so if it's not showing up that's why bestie.
-xen-domid id — specifies the xen guest domain id (XEN only).
-xen-attach — attaches to an existing xen domain. libxl will use this when starting QEMU (XEN only). It also restricts the set of available xen operations to the specified domain id (XEN only).
-no-reboot — exits instead of rebooting. Simple as. 💀
-no-shutdown — don't exit QEMU when the guest shuts down, just stop the emulation instead. This is lowkey so useful — it lets you, for instance, switch to the monitor and commit changes to the disk image.
-action event=action — the action parameter exists to modify QEMU's default behavior when certain guest events happen. It's a generic way to specify the same behaviors that get modified by the -no-reboot and -no-shutdown parameters. So like, the glow-up version. ✨

Examples:

-action panic=none -action reboot=shutdown,shutdown=pause -device i6300esb -action watchdog=pause

-loadvm file — starts right away with a saved state (this is loadvm in the monitor).
-daemonize — daemonizes the QEMU process after initialization. QEMU won't detach from standard IO until it's ready to receive connections on any of its devices. This is such a handy way for external programs to launch QEMU without having to deal with initialization race conditions. 🫶
-option-rom file — loads the contents of file as an option ROM. Great for loading things like EtherBoot.
-rtc [base=utc|localtime|datetime][,clock=host|rt|vm][,driftfix=none|slew] — okay so here's the tea. ☕

Set base to utc or localtime to let the RTC start at the current UTC or local time respectively. localtime is required for a correct date in MS-DOS or Windows. Wanna start at a specific point in time? Give it datetime in the format 2006-06-17T16:01:21 or 2006-06-17. The default base is UTC.

By default the RTC is driven by the host system time. This lets you use the RTC as an accurate reference clock inside the guest — especially if the host time is smoothly following an accurate external reference clock, e.g. via NTP. If you want to isolate the guest time from the host, set clock to rt instead, which gives you a host monotonic clock if the host supports it. To even prevent the RTC from progressing during suspension, set clock to vm (virtual clock). 'clock=vm' is recommended especially in icount mode so you preserve determinism — but note that in icount mode the speed of the virtual clock is variable and can in general differ from the host clock. 🙈

Enable driftfix (i386 targets only) if you're dealing with time drift problems, specifically with Windows' ACPI HAL. This option will try to figure out how many timer interrupts weren't processed by the Windows guest and will re-inject them. Fixing what the guest fumbled, iconic.

-icount [shift=N|auto][,align=on|off][,sleep=on|off][,rr=record|replay,rrfile=filename[,rrsnapshot=snapshot]] — enables the virtual instruction counter. The virtual cpu will execute one instruction every 2^N ns of virtual time. If auto is specified then the virtual cpu speed gets automatically adjusted to keep virtual time within a few seconds of real time. 🕰️

Note that while this option can give you deterministic behavior, it does not provide cycle-accurate emulation. Modern CPUs contain superscalar out-of-order cores with complex cache hierarchies. The number of instructions executed often has little or no correlation with actual performance. Fr fr.

When the virtual cpu is sleeping, virtual time advances at default speed unless sleep=off is specified. With sleep=off, the virtual time jumps to the next timer deadline instantly whenever the virtual cpu goes into sleep mode, and won't advance if no timer is enabled. This behavior gives deterministic execution times from the guest's point of view. The default if icount is enabled is sleep=on. And heads up: sleep=off cannot be used together with either shift=auto or align=on. Pick your fighter.

align=on activates the delay algorithm, which tries to synchronise the host clock and the virtual clock. The goal is to have a guest running at the real frequency imposed by the shift option. Whenever the guest clock is behind the host clock and align=on is specified, we print a message to the user to inform about the delay. Currently this option doesn't work when shift is auto. Note: the sync algorithm will work for those shift values for which the guest clock runs ahead of the host clock. Typically this happens when the shift value is high (how high depends on the host machine). The default if icount is enabled is align=off.

When the rr option is specified, deterministic record/replay is enabled. The rrfile= option must also be provided to specify the path to the replay log. In record mode, data is written to this file; in replay mode it's read back. If the rrsnapshot option is given, then it specifies a VM snapshot name. In record mode, a new VM snapshot with the given name is created at the start of execution recording. In replay mode, this option specifies the snapshot name used to load the initial VM state. 🎬

-watchdog-action action — the action controls what QEMU does when the watchdog timer expires. The default is reset (forcefully reset the guest). Other possible actions are: shutdown (attempt to gracefully shutdown the guest), poweroff (forcefully poweroff the guest), inject-nmi (inject a NMI into the guest), pause (pause the guest), debug (print a debug message and continue), or none (do nothing).

Okay real talk: the shutdown action requires that the guest responds to ACPI signals, which it may not be able to do in the sort of situations where the watchdog would have expired — and thus -watchdog-action shutdown is not recommended for production use. You've been warned bestie. 🚨

Examples:

-device i6300esb -watchdog-action pause

-echr numeric_ascii_value — changes the escape character used for switching to the monitor when using monitor and serial sharing. The default is 0x01 when using the -nographic option. 0x01 is equal to pressing Control-a. You can select a different character from the ascii control keys, where 1 through 26 map to Control-a through Control-z. For instance, you could use either of the following to change the escape character to Control-t. 🎀

-echr 0x14; -echr 20

The -incoming option specifies the migration channel for an incoming migration. It may be used multiple times to specify multiple migration channel types. The channel type is specified in <channel>, or is 'main' for all other forms of -incoming. If multiple -incoming options are specified for a channel type, the last one takes precedence. Last one wins, periodt. 👑

-incoming tcp:[host]:port[,to=maxport][,ipv4=on|off][,ipv6=on|off]
-incoming rdma:host:port[,ipv4=on|off][,ipv6=on|off] — prepares for incoming migration, listening on a given tcp port.
-incoming unix:socketpath — prepares for incoming migration, listening on a given unix socket.
-incoming fd:fd — accepts incoming migration from a given file descriptor.
-incoming file:filename[,offset=offset] — accepts incoming migration from a given file starting at offset. offset allows the common size suffixes, or a 0x prefix, but not both. Choose one, babe.
-incoming exec:cmdline — accepts incoming migration as an output from a specified external command.
-incoming <channel> — accepts incoming migration on the migration channel. For the syntax of <channel>, see the QAPI documentation of MigrationChannel. Examples:

-incoming '{"channel-type": "main",
            "addr": { "transport": "socket",
                      "type": "unix",
                      "path": "my.sock" }}'

-incoming main,addr.transport=socket,addr.type=unix,addr.path=my.sock

-incoming defer — waits for the URI to be specified via migrate_incoming. The monitor can be used to change settings (such as migration parameters) prior to issuing the migrate_incoming, so the migration can begin. Chill and wait for your moment. 🦋
-only-migratable — migratable devices only, bestie, that's the vibe. Devices will not be allowed to enter an unmigratable state. periodt.
-nodefaults — no default devices for you, girl. Normally QEMU sets the default devices like serial port, parallel port, virtual console, monitor device, VGA adapter, floppy and CD-ROM drive and others. The -nodefaults option will disable all those default devices. it's giving minimalist era 💅
-prom-env variable=value — set an OpenBIOS nvram variable to the given value (PPC, SPARC only, iykyk).

qemu-system-sparc -prom-env 'auto-boot?=false' \
 -prom-env 'boot-device=sd(0,2,0):d' -prom-env 'boot-args=linux single'

qemu-system-ppc -prom-env 'auto-boot?=false' \
 -prom-env 'boot-device=hd:2,\yaboot' \
 -prom-env 'boot-args=conf=hd:2,\yaboot.conf'

-semihosting — turn on Semihosting mode (ARM, M68K, Xtensa, MIPS, RISC-V only). 🦋

⚠️ ok so real talk: this allows guest direct access to the host filesystem, so should only be used with a trusted guest OS. like, trusted trusted. no randos.

See the -semihosting-config option documentation for further information about the facilities this enables.

-semihosting-config [enable=on|off][,target=native|gdb|auto][,chardev=id][,userspace=on|off][,arg=str[,...]] — enable and configure Semihosting (ARM, M68K, Xtensa, MIPS, RISC-V only).

⚠️ same warning as above bestie: this allows guest direct access to the host filesystem, so should only be used with a trusted guest OS. 💀

target=native|gdb|auto — defines where the semihosting calls will be addressed: to QEMU (native) or to GDB (gdb). The default is auto, which means gdb during debug sessions and native otherwise. she's flexible like that ✨
chardev=str1 — send the output to a chardev backend output for native or auto output when not in gdb.
userspace=on|off — allows code running in guest userspace to access the semihosting interface. The default is that only privileged guest code can make semihosting calls. Note that setting userspace=on should only be used if all guest code is trusted (for example, in bare-metal test case code). 🙈
arg=str1,arg=str2,... — lets you pass input arguments, and can be used multiple times to build up a list. The old-style -kernel/-append method of passing a command line is still supported for backward compatibility. If both the --semihosting-config arg and the -kernel/-append are specified, the former is passed to semihosting as it always takes precedence. main character energy, obviously 👑

-sandbox arg[,obsolete=string][,elevateprivileges=string][,spawn=string][,resourcecontrol=string] — enable Seccomp mode 2 system call filter. 'on' will enable syscall filtering and 'off' will disable it. The default is 'off'.
- obsolete=string — enable Obsolete system calls.
- elevateprivileges=string — disable set*uid|gid system calls.
- spawn=string — disable *fork and execve.
- resourcecontrol=string — disable process affinity and schedular priority.
-readconfig file — read device configuration from file. This approach is useful when you want to spawn a QEMU process with so many command line options but you don't want to exceed the command line character limit. she said "my options are too long for you" 😭
-no-user-config — the -no-user-config option makes QEMU not load any of the user-provided config files on sysconfdir.
-trace [[enable=]pattern][,events=file][,file=file] — specify tracing options. detective mode 🔍
- [enable=]PATTERN — immediately enable events matching PATTERN (either event name or a globbing pattern). This option is only available if QEMU has been compiled with the simple, log or ftrace tracing backend. To specify multiple events or patterns, specify the -trace option multiple times.

Use -trace help to print a list of names of trace points.

events=FILE — immediately enable events listed in FILE. The file must contain one event name (as listed in the trace-events-all file) per line; globbing patterns are accepted too. This option is only available if QEMU has been compiled with the simple, log or ftrace tracing backend.
file=FILE — log output traces to FILE. This option is only available if QEMU has been compiled with the simple tracing backend.

-plugin file=file[,argname=argvalue] — load a plugin. 🧚
- file=file — load the given plugin from a shared library file.
- argname=argvalue — argument passed to the plugin. (Can be given multiple times.)
-run-with [async-teardown=on|off][,chroot=dir][,exit-with-parent=on|off][,user=username|uid:gid] — set QEMU process lifecycle options. 🌈
- async-teardown=on enables asynchronous teardown. A new process called "cleanup/<QEMU_PID>" will be created at startup sharing the address space with the main QEMU process, using clone. It will wait for the main QEMU process to terminate completely, and then exit. This allows QEMU to terminate very quickly even if the guest was huge, leaving the teardown of the address space to the cleanup process. Since the cleanup process shares the same cgroups as the main QEMU process, accounting is performed correctly. This only works if the cleanup process is not forcefully killed with SIGKILL before the main QEMU process has terminated completely.
- chroot=dir can be used for doing a chroot to the specified directory immediately before starting the guest execution. This is especially useful in combination with user=....
- exit-with-parent=on causes QEMU to exit if the parent process of QEMU exits. This can be used when QEMU runs a captive appliance, where the lifetime of the appliance is scoped to the parent process. In case the parent process crashes, QEMU is still cleaned up. This only works on Linux, FreeBSD and macOS platforms. 🫶
- user=username or user=uid:gid can be used to drop root privileges before starting guest execution. QEMU will use the setuid and setgid system calls to switch to the specified identity. Note that the user=username syntax will also apply the full set of supplementary groups for the user, whereas the user=uid:gid will use only the gid group.
-msg [timestamp[=on|off]][,guest-name[=on|off]] — control error message format. ✨
- timestamp=on|off — prefix messages with a timestamp. Default is off.
- guest-name=on|off — prefix messages with guest name but only if -name guest option is set, otherwise the option is ignored. Default is off.
-dump-vmstate file — dump json-encoded vmstate information for the current machine type to file in file.
-enable-sync-profile — enable synchronization profiling. get that data, girl 📊
-perfmap — generate a map file for Linux perf tools that will allow basic profiling information to be broken down into basic blocks.
-jitdump — generate a dump file for Linux perf tools that maps basic blocks to symbol names, line numbers and JITted code.

🌈 Generic object creation 🌈

-object typename[,prop1=value1,...] — create a new object of type typename setting properties in the order they are specified. Note that the 'id' property must be set. These objects are placed in the /objects path. 💖
- -object memory-backend-file,id=id,size=size,mem-path=dir,share=on|off,discard-data=on|off,merge=on|off,dump=on|off,prealloc=on|off,host-nodes=host-nodes,policy=default|preferred|bind|interleave,align=align,offset=offset,readonly=on|off,rom=on|off|auto — creates a memory file backend object, which can be used to back the guest RAM with huge pages.

The id parameter is a unique ID that will be used to reference this memory region in other parameters, e.g. -numa, -device nvdimm, etc.

The size option provides the size of the memory region, and accepts common suffixes, e.g. 500M.

The mem-path provides the path to either a shared memory or huge page filesystem mount.

The share boolean option determines whether the memory region is marked as private to QEMU, or shared. The latter allows a co-operating external process to access the QEMU memory region.

Setting share=on might affect the ability to configure NUMA bindings for the memory backend under some circumstances, see Documentation/vm/numa_memory_policy.txt on the Linux kernel source tree for additional details.

Setting the discard-data boolean option to on indicates that file contents can be destroyed when QEMU exits, to avoid unnecessarily flushing data to the backing file. Note that discard-data is only an optimization, and QEMU might not discard file contents if it aborts unexpectedly or is terminated using SIGKILL. 💀

The merge boolean option enables memory merge, also known as MADV_MERGEABLE, so that Kernel Samepage Merging will consider the pages for memory deduplication.

Setting the dump boolean option to off excludes the memory from core dumps. This feature is also known as MADV_DONTDUMP.

The prealloc boolean option enables memory preallocation.

The host-nodes option binds the memory range to a list of NUMA host nodes.

The policy option sets the NUMA policy to one of the following values:

default — default host policy
preferred — prefer the given host node list for allocation
bind — restrict memory allocation to the given host node list
interleave — interleave memory allocations across the given host node list

The align option sets the base address alignment for when QEMU does its mmap(2) thing on mem-path, and it takes the usual suffixes, like 2M 🎀. Some backends you point at with mem-path are picky and need a different alignment than the default QEMU uses — like the device DAX /dev/dax0.0 needs 2M alignment, not 4K. For those situations you just hand over the alignment you need with this option, and slay ✨.
The offset option sets the offset into the target file where the region starts. Use it to back multiple regions off one single file, iykyk 🫶.
The pmem option says whether the backing file you gave in mem-path lives in host persistent memory that's reachable through the SNIA NVM programming model (think Intel NVDIMM). Set pmem to on and QEMU does the necessary operations to guarantee its own writes to mem-path actually persist — like in vNVDIMM label emulation and live migration, bestie 💖. It also maps the backend-file with the MAP_SYNC flag, which keeps the file metadata in sync for mem-path even if the host crashes or loses power. Heads up though: MAP_SYNC needs support from both the host kernel (Linux kernel 4.15 and up) and the filesystem of mem-path mounted with the DAX option. No cap.
The readonly option says whether the backing file gets opened read-only or read-write. Read-write is the default, periodt.
The rom option says whether to create Read Only Memory (ROM) that the VM can't modify. Any write attempt to that ROM gets denied, fr fr. Most use cases actually want proper RAM instead of ROM, ngl. But some specific use cases, like R/O NVDIMMs, can benefit from ROM. Set it to on and you get ROM; set it to off and you get writable RAM; set it to auto (the default) and it uses the value of the readonly option. This option is mainly a lifesaver when you want writable RAM in configurations that would traditionally create ROM before the rom option even existed: VM templating, where you want to open a file readonly (readonly=on) and mark the memory private for QEMU (share=off). For that use case you need writable RAM instead of ROM, so you also want to set rom=off 👑.

Creates a memory backend object, which can be used to back the guest RAM 🧚. Memory backend objects give you way more control than the -m option that's traditionally used to define guest RAM. For a description of the options, go check out memory-backend-file, bestie 💜.

Creates an anonymous memory file backend object, which lets QEMU share the memory with an external process — like when you're using vhost-user, you know the vibe 💅. The memory is allocated with memfd plus optional sealing. (Linux only, sorry babes 🌸.)

The seal option creates a sealed-file, which blocks any further resizing of the memory. It's 'on' by default.
The hugetlb option says the file to be created lives in the hugetlbfs filesystem (since Linux 4.14). Used together with the hugetlb option, the hugetlbsize option sets the hugetlb page size on systems that support multiple hugetlb page sizes — and it must be a power of 2 value supported by the system, no exceptions 🔥.

In some versions of Linux, the hugetlb option is incompatible with the seal option (you need at least Linux 4.16 for them to coexist).

For a description of the other options, go peek at memory-backend-file.

The share boolean option is on by default with memfd ✨.

Creates a POSIX shared memory backend object, which lets QEMU share the memory with an external process — again, think vhost-user 🦋.

memory-backend-shm is a more portable and less featureful version of memory-backend-memfd. That means you can use it on any POSIX system, especially when memfd isn't supported. Iconic honestly.

For a description of the options, refer to memory-backend-file.

The share boolean option is on by default with shm. Setting it to off will cause a failure during allocation, because this backend simply doesn't support that — so don't try it 😭.

-object iommufd,id=id[,fd=fd]

Creates an iommufd backend which lets you control DMA mapping through the /dev/iommu device 🎀.

The id parameter is a unique ID that frontends (like vfio-pci of vdpa) will use to connect with the iommufd backend.
The fd parameter is an optional pre-opened file descriptor that comes from opening /dev/iommu. Usually the iommufd is shared across all subsystems, which brings you the benefit of centralized reference counting. Main character energy 👑.

-object rng-builtin,id=id

Creates a random number generator backend that gets entropy from QEMU builtin functions 🌈. The id parameter is a unique ID that'll be used to reference this entropy backend from the virtio-rng device. By default, the virtio-rng device uses this RNG backend. Obsessed with how easy that is 💖.

-object rng-random,id=id,filename=/dev/random

Creates a random number generator backend that gets entropy from a device on the host 🍓. The id parameter is a unique ID that'll be used to reference this entropy backend from the virtio-rng device. The filename parameter says which file to grab entropy from, and if you omit it, it defaults to /dev/urandom.

-object rng-egd,id=id,chardev=chardevid

Creates a random number generator backend that gets entropy from an external daemon running on the host ✨. The id parameter is a unique ID that'll be used to reference this entropy backend from the virtio-rng device. The chardev parameter is the unique ID of a character device backend that provides the connection to the RNG daemon.

-object tls-creds-anon,id=id,endpoint=endpoint,dir=/path/to/cred/dir,verify-peer=on|off

Creates a TLS anonymous credentials object, which can be used to provide TLS support on network backends 🔐💜. The id parameter is a unique ID that network backends will use to access the credentials. The endpoint is either server or client, depending on whether the QEMU network backend using the credentials is acting as a client or as a server. If verify-peer is enabled (which is the default) then once the handshake is done, the peer credentials get verified — though for anonymous credentials this is a total no-op, lowkey 😅.

The dir parameter tells QEMU where to find the credential files. For server endpoints, this directory may contain a file dh-params.pem that provides diffie-hellman parameters to use for the TLS server. If that file is missing, QEMU will generate a set of DH parameters at startup. Heads up bestie: that is a computationally expensive operation that consumes random pool entropy, so it's recommended you generate a persistent set of parameters upfront and save them 💀.

-object tls-creds-psk,id=id,endpoint=endpoint,dir=/path/to/keys/dir[,username=username]

Creates a TLS Pre-Shared Keys (PSK) credentials object, which can be used to provide TLS support on network backends 🎀. The id parameter is a unique ID that network backends will use to access the credentials. The endpoint is either server or client, depending on whether the QEMU network backend using the credentials is acting as a client or as a server. For clients only, username is the username that gets sent to the server. If you omit it, it defaults to "qemu".

The dir parameter tells QEMU where to find the keys file. It's called "dir/keys.psk" and it contains "username:key" pairs. The easiest way to create this file is with the GnuTLS psktool program, iykyk 🫶.

For server endpoints, dir may also contain a file dh-params.pem providing diffie-hellman parameters to use for the TLS server. If the file is missing, QEMU will generate a set of DH parameters at startup. Again, that's a computationally expensive operation that consumes random pool entropy, so it's recommended you generate a persistent set of parameters upfront and save them 🌸.

-object tls-creds-x509,id=id,endpoint=endpoint,dir=/path/to/cred/dir,priority=priority,verify-peer=on|off,passwordid=id

Creates a TLS anonymous credentials object, which can be used to provide TLS support on network backends 💖. The id parameter is a unique ID that network backends will use to access the credentials. The endpoint is either server or client, depending on whether the QEMU network backend using the credentials is acting as a client or as a server. If verify-peer is enabled (and yes, that's the default) then once the handshake is done, the peer credentials get verified. With x509 certificates, this implies that the clients must be given valid client certificates too — so like, actually do that, bestie 😭🔥.

Okay so the dir parameter is literally the vibe-check for where QEMU goes to find all your credential files, bestie. 📁✨

For server endpoints, this directory may contain a file called dh-params.pem, and that one's holding the diffie-hellman parameters you'd use for the TLS server. If that file's just… not there? QEMU will generate a whole set of DH parameters at startup. But heads up: that's a computationally expensive operation that eats random pool entropy for breakfast, so the recommendation is fr fr to generate a persistent set of parameters upfront and save them. Do it once, thank yourself later. 💅

For x509 certificate credentials, the directory is gonna have further files with the x509 certificates in them. Those certificates have to be stored in PEM format, and the filenames are, like, a whole lineup:

ca-cert.pem
ca-crl.pem (optional, no pressure)
server-cert.pem (servers only 🫶)
server-key.pem (servers only 🫶)
client-cert.pem (clients only 🫶)
client-key.pem (clients only 🫶)

For the server-key.pem and client-key.pem files — which, btw, contain sensitive private keys, so keep those close — it's possible to use an encrypted version by providing the passwordid parameter. That gives you the ID of a previously created secret object containing the password for decryption. 🔐

The priority parameter lets you override the global default priority that gnutls uses. When is that useful? Say a system administrator needs to use a weaker set of crypto priorities for QEMU without potentially forcing that weakness onto literally every other application — this is your girl. Or, flip side, if someone wants a stronger default for QEMU than for all other applications, they can do that through this parameter too. Its format is a gnutls priority string, as described at <https://gnutls.org/manual/html_node/Priority-Strings.html>. 📚

🌸 `-object tls-cipher-suites,id=id,priority=priority` 🌸

This creates a TLS cipher suites object, and it's the thing you use to control which TLS cipher/protocol algorithms applications are even permitted to use. Gatekeeping, but make it cryptography. 👑

The id parameter is a unique ID which frontends will use to access the ordered list of permitted TLS cipher suites from the host.

The priority parameter allows you to override the global default priority used by gnutls. Same deal as before: handy if a system administrator needs a weaker set of crypto priorities for QEMU without potentially forcing the weakness onto all applications, or conversely if someone wants a stronger default for QEMU than for all other applications — they can do this through this parameter. Its format is a gnutls priority string, described at <https://gnutls.org/manual/html_node/Priority-Strings.html>.

One iconic use of this object is controlling UEFI HTTPS Boot. The tls-cipher-suites object exposes the ordered list of permitted TLS cipher suites from the host side to the guest firmware, via fw_cfg. The list is represented as an array of IANA_TLS_CIPHER objects. The firmware then uses that IANA_TLS_CIPHER array for configuring guest-side TLS.

In the following example, the priority at which the host-side policy is retrieved is given by the priority property. And since QEMU uses GNUTLS, priority=@SYSTEM may be used to refer to /etc/crypto-policies/back-ends/gnutls.config.

# qemu-system-x86_64 \
    -object tls-cipher-suites,id=mysuite0,priority=@SYSTEM \
    -fw_cfg name=etc/edk2/https/ciphers,gen_id=mysuite0

🦋 `-object filter-buffer,id=id,netdev=netdevid,interval=t[,queue=all|rx|tx][,status=on|off][,position=head|tail|id=<id>][,insert=behind|before]` 🦋

Interval t can't be 0 — not even a little bit. This filter batches the packet delivery: all packets arriving in a given interval on netdev netdevid are delayed until the end of the interval. Interval is in microseconds. status is optional and indicates whether the netfilter is on (enabled) or off (disabled) — the default status for netfilter will be 'on'. ✨

queue all|rx|tx is an option that can be applied to any netfilter:

all: the filter is attached both to the receive and the transmit queue of the netdev (default).
rx: the filter is attached to the receive queue of the netdev, where it will receive packets sent to the netdev.
tx: the filter is attached to the transmit queue of the netdev, where it will receive packets sent by the netdev.

position head|tail|id=<id> is an option to specify where the filter should be inserted in the filter list. It can be applied to any netfilter.

head: the filter is inserted at the head of the filter list, before any existing filters.
tail: the filter is inserted at the tail of the filter list, behind any existing filters (default).
id=<id>: the filter is inserted before or behind the filter specified by <id> — see the insert option below.

insert behind|before is an option to specify where to insert the new filter relative to the one specified with position=id=<id>. It can be applied to any netfilter.

before: insert before the specified filter.
behind: insert behind the specified filter (default).

💖 `-object filter-mirror,id=id,netdev=netdevid,outdev=chardevid,queue=all|rx|tx[,vnet_hdr_support][,position=head|tail|id=<id>][,insert=behind|before]` 💖

filter-mirror on netdev netdevid mirrors net packets to chardev chardevid. And if it has the vnet_hdr_support flag, filter-mirror will mirror packets with vnet_hdr_len. 🪞

🎀 `-object filter-redirector,id=id,netdev=netdevid,indev=chardevid,outdev=chardevid,queue=all|rx|tx[,vnet_hdr_support][,position=head|tail|id=<id>][,insert=behind|before]` 🎀

filter-redirector on netdev netdevid redirects the filter's net packets to chardev chardevid, and redirects indev's packets to the filter. If it has the vnet_hdr_support flag, filter-redirector will redirect packets with vnet_hdr_len.

To create a filter-redirector we need to differ the outdev id from the indev id — the id can not be the same, okay? 🙅 We can just use indev or outdev, but at least one of indev or outdev needs to be specified.

🌈 `-object filter-rewriter,id=id,netdev=netdevid,queue=all|rx|tx,[vnet_hdr_support][,position=head|tail|id=<id>][,insert=behind|before]` 🌈

filter-rewriter is a part of the COLO project. It will rewrite tcp packets to secondary from primary to keep the secondary tcp connection, and rewrite tcp packets to primary from secondary so that the tcp packet can be handled by the client. If it has the vnet_hdr_support flag, we can parse packets with a vnet header. 🧚

usage: colo secondary:

-object filter-redirector,id=f1,netdev=hn0,queue=tx,indev=red0
-object filter-redirector,id=f2,netdev=hn0,queue=rx,outdev=red1
-object filter-rewriter,id=rew0,netdev=hn0,queue=all

🍓 `-object filter-dump,id=id,netdev=dev[,file=filename][,maxlen=len][,position=head|tail|id=<id>][,insert=behind|before]` 🍓

Dumps the network traffic on netdev dev to the file specified by filename. At most len bytes (64k by default) per packet are stored. The file format is libpcap, so it can be analyzed with tools such as tcpdump or Wireshark. 📼

👑 `-object colo-compare,id=id,primary_in=chardevid,secondary_in=chardevid,outdev=chardevid,iothread=id[,vnet_hdr_support][,notify_dev=id][,compare_timeout=@var{ms}][,expired_scan_cycle=@var{ms}][,max_queue_size=@var{size}]` 👑

colo-compare gets packets from primary_in chardevid and secondary_in, then compares whether the payload of the primary packet and the secondary packet are the same. If they're the same, it outputs the primary packet to out_dev; otherwise it notifies the COLO-framework to do a checkpoint and sends the primary packet to out_dev. To improve efficiency, we need to put the task of comparison in another iothread. If it has the vnet_hdr_support flag, colo-compare will send/recv packets with vnet_hdr_len.

The <compare_timeout=@var{ms>} determines the maximum time the colo-compare holds the packet. The <expired_scan_cycle=@var{ms>} sets the period of scanning expired primary node network packets. The <max_queue_size=@var{size>} sets the max compare queue size depending on the user environment. If a user wants to use Xen COLO, they need to add the notify_dev to notify the Xen colo-frame to do a checkpoint.

🫶 COLO-compare must be used with the help of filter-mirror, filter-redirector and filter-rewriter. No solo runs, bestie.

💜 KVM COLO 💜

primary:

-netdev tap,id=hn0,vhost=off
-device e1000,id=e0,netdev=hn0,mac=52:a4:00:12:78:66
-chardev socket,id=mirror0,host=3.3.3.3,port=9003,server=on,wait=off
-chardev socket,id=compare1,host=3.3.3.3,port=9004,server=on,wait=off
-chardev socket,id=compare0,host=3.3.3.3,port=9001,server=on,wait=off
-chardev socket,id=compare0-0,host=3.3.3.3,port=9001
-chardev socket,id=compare_out,host=3.3.3.3,port=9005,server=on,wait=off
-chardev socket,id=compare_out0,host=3.3.3.3,port=9005
-object iothread,id=iothread1
-object filter-mirror,id=m0,netdev=hn0,queue=tx,outdev=mirror0
-object filter-redirector,netdev=hn0,id=redire0,queue=rx,indev=compare_out
-object filter-redirector,netdev=hn0,id=redire1,queue=rx,outdev=compare0
-object colo-compare,id=comp0,primary_in=compare0-0,secondary_in=compare1,outdev=compare_out0,iothread=iothread1

so the tail end of that whole COLO situation — the secondary half — looks like this, bestie:

secondary:
-netdev tap,id=hn0,vhost=off
-device e1000,netdev=hn0,mac=52:a4:00:12:78:66
-chardev socket,id=red0,host=3.3.3.3,port=9003
-chardev socket,id=red1,host=3.3.3.3,port=9004
-object filter-redirector,id=f1,netdev=hn0,queue=tx,indev=red0
-object filter-redirector,id=f2,netdev=hn0,queue=rx,outdev=red1

and now the Xen COLO version, because of course there's a Xen version 💅

Xen COLO

primary:

-netdev tap,id=hn0,vhost=off
-device e1000,id=e0,netdev=hn0,mac=52:a4:00:12:78:66
-chardev socket,id=mirror0,host=3.3.3.3,port=9003,server=on,wait=off
-chardev socket,id=compare1,host=3.3.3.3,port=9004,server=on,wait=off
-chardev socket,id=compare0,host=3.3.3.3,port=9001,server=on,wait=off
-chardev socket,id=compare0-0,host=3.3.3.3,port=9001
-chardev socket,id=compare_out,host=3.3.3.3,port=9005,server=on,wait=off
-chardev socket,id=compare_out0,host=3.3.3.3,port=9005
-chardev socket,id=notify_way,host=3.3.3.3,port=9009,server=on,wait=off
-object filter-mirror,id=m0,netdev=hn0,queue=tx,outdev=mirror0
-object filter-redirector,netdev=hn0,id=redire0,queue=rx,indev=compare_out
-object filter-redirector,netdev=hn0,id=redire1,queue=rx,outdev=compare0
-object iothread,id=iothread1
-object colo-compare,id=comp0,primary_in=compare0-0,secondary_in=compare1,outdev=compare_out0,notify_dev=notify_way,iothread=iothread1

secondary:

-netdev tap,id=hn0,vhost=off
-device e1000,netdev=hn0,mac=52:a4:00:12:78:66
-chardev socket,id=red0,host=3.3.3.3,port=9003
-chardev socket,id=red1,host=3.3.3.3,port=9004
-object filter-redirector,id=f1,netdev=hn0,queue=tx,indev=red0
-object filter-redirector,id=f2,netdev=hn0,queue=rx,outdev=red1

ngl, if you wanna know the deets of that command line above, go read the colo-compare git log. that's the source of truth, no cap 📜

-object cryptodev-backend-builtin,id=id[,queues=queues] — spins up a cryptodev backend that runs crypto operations straight from the QEMU cipher APIs. the id is a unique ID you'll use to point at this backend from the virtio-crypto device. queues is optional and says how many queues the cryptodev backend has — default is 1.

# qemu-system-x86_64 \
  [...] \
      -object cryptodev-backend-builtin,id=cryptodev0 \
      -device virtio-crypto-pci,id=crypto0,cryptodev=cryptodev0 \
  [...]

-object cryptodev-vhost-user,id=id,chardev=chardevid[,queues=queues] — makes a vhost-user cryptodev backend, backed by a chardev called chardevid. same deal: id is a unique ID you reference from the virtio-crypto device. the chardev has to be a unix domain socket backed one. vhost-user uses a specifically defined protocol to pass vhost ioctl replacement messages over to an application sitting on the other end of the socket. queues is optional and sets the queue number of the cryptodev backend for multiqueue vhost-user — default is 1 again.

# qemu-system-x86_64 \
  [...] \
      -chardev socket,id=chardev0,path=/path/to/socket \
      -object cryptodev-vhost-user,id=cryptodev0,chardev=chardev0 \
      -device virtio-crypto-pci,id=crypto0,cryptodev=cryptodev0 \
  [...]

-object secret,id=id,data=string,format=raw|base64[,keyid=secretid,iv=string]
-object secret,id=id,file=filename,format=raw|base64[,keyid=secretid,iv=string] — defines a secret for holding a password, an encryption key, or honestly any sensitive data you've got. you can hand the sensitive data over directly with the data parameter, or indirectly with the file parameter. heads up bestie: using data is insecure unless the sensitive data is encrypted. 🚨

the sensitive data can come in raw format (that's the default) or base64. when it's encoded as JSON, the raw format only supports valid UTF-8 characters, so base64 is the recommended move for sending binary data. QEMU will convert from whichever format you gave it into the format it needs internally. e.g. an RBD password can be handed over in raw format, even though it'll be base64 encoded when it gets passed along to the RBD server. ✨

for extra protection, you can encrypt the data tied to a secret using the AES-256-CBC cipher. you know encryption's on when you supply the keyid and iv parameters. keyid gives the ID of a previously defined secret holding the AES-256 decryption key — that key should be 32-bytes long and base64 encoded. iv gives the random initialization vector used to encrypt this particular secret, and it should be a base64 encrypted string of the 16-byte IV.

the simplest (and, again, insecure) usage is just handing the secret over inline:

# qemu-system-x86_64 -object secret,id=sec0,data=letmein,format=raw

the simplest secure usage is to provide the secret through a file:

# printf "letmein" > mypasswd.txt
# QEMU_SYSTEM_MACRO -object secret,id=sec0,file=mypasswd.txt,format=raw

for even greater security, use AES-256-CBC. to illustrate, think about the openssl command line tool, which can encrypt the data. note that when you're encrypting, the plaintext must be padded to the cipher block size (32 bytes) using the standard PKCS#5/6 compatible padding algorithm.

first, a master key needs to be created in base64 encoding:

# openssl rand -base64 32 > key.b64
# KEY=$(base64 -d key.b64 | hexdump  -v -e '/1 "%02X"')

each secret you want to encrypt needs its own random initialization vector generated. these do not need to be kept secret 🔓

# openssl rand -base64 16 > iv.b64
# IV=$(base64 -d iv.b64 | hexdump  -v -e '/1 "%02X"')

now the secret to be defined can be encrypted — here we're telling openssl to base64 encode the result, but it could be left as raw bytes if you want:

# SECRET=$(printf "letmein" |
           openssl enc -aes-256-cbc -a -K $KEY -iv $IV)

when you launch QEMU, create a master secret pointing at key.b64 and say that's what should decrypt the user password. then pass the contents of iv.b64 to the second secret:

# qemu-system-x86_64 \
    -object secret,id=secmaster0,format=base64,file=key.b64 \
    -object secret,id=sec0,keyid=secmaster0,format=base64,\
        data=$SECRET,iv=$(<iv.b64)

-object sev-guest,id=id,cbitpos=cbitpos,reduced-phys-bits=val,[sev-device=string,policy=policy,handle=handle,dh-cert-file=file,session-file=file,kernel-hashes=on|off] — creates a Secure Encrypted Virtualization (SEV) guest object, which you can use to get guest memory encryption support on AMD processors. 👑

when memory encryption is on, one of the physical address bits (aka the C-bit) gets used to mark whether a memory page is protected. cbitpos supplies the C-bit position. that position is Host-family dependent, so you have to hand over this value. on EPYC, the value should be 47.

when memory encryption is on, we lose certain bits in the physical address space. reduced-phys-bits supplies the number of bits we lose there. just like the C-bit, this value is Host-family dependent. on EPYC, a guest loses a maximum of 1 bit, so the value should be 1.

sev-device gives the device file to use for talking to the SEV firmware running inside the AMD Secure Processor. the default device is '/dev/sev'. if the hardware supports memory encryption, then the /dev/sev devices get created by the CCP driver.

policy supplies the guest policy to be enforced by the SEV firmware, restricting what configuration and operational commands the hypervisor can perform on this guest. the policy should be provided by the guest owner, and it's bound to the guest — it cannot be changed for the whole lifetime of the guest. default is 0.

if the guest policy allows sharing the key with another SEV guest, then handle can be used to supply the handle of the guest you're sharing the key from.

dh-cert-file and session-file supply the guest owner's Public Diffie-Hillman key defined in the SEV spec. the PDH and session parameters get used for establishing a cryptographic session with the guest owner to negotiate the keys used for attestation. the file must be encoded in base64.

kernel-hashes adds the hashes of the given kernel/initrd/cmdline to a designated guest firmware page for measured Linux boot with -kernel. the default is off. (Since 6.2)

e.g. to launch a SEV guest:

# qemu-system-x86_64 \
    ...... \
    -object sev-guest,id=sev0,cbitpos=47,reduced-phys-bits=1 \
    -machine ...,memory-encryption=sev0 \
    .....

-object igvm-cfg,file=file — makes an IGVM config object, and what that does is set up the guest's initial state from a file that follows the Independent Guest Virtual Machine (IGVM) file format. 💖

Heads up bestie: rn this is only supported by -machine q35 and -machine pc. Like, that's it. That's the whole guest list.

The file parameter is where you point at the IGVM file you wanna load. Once you hand it over, that IGVM file gets used to populate the virtual machine's initial memory and, depending on the platform, it can also define the initial processor state, the memory map and parameters. So it's kinda doing a lot of heavy lifting. 💅

So here's the tea: the IGVM file is expected to contain the firmware for the virtual machine. Which means you cannot hand an igvm-cfg object over at the same time as any other way of specifying firmware — like the -bios parameter on x86 machines. Nope. Pick one. 🙈

e.g. to launch a machine providing the firmware in an IGVM file:

# qemu-system-x86_64 \
    ...... \
    -object igvm-cfg,id=igvm0,file=bios.igvm \
    -machine ...,igvm-cfg=igvm0 \
    .....

-object authz-simple,id=id,identity=string — makes an authorization object that will control access to network services. 🔐

The identity parameter is identifies the user and its format depends on the network service that authorization object is associated with. For authorizing based on TLS x509 certificates, the identity must be the x509 distinguished name. And careful, okay? You gotta take care to escape any commas in the distinguished name. Every single one. Don't skip it. 😭

An example authorization object to validate a x509 distinguished name would look like:

# qemu-system-x86_64 \
    ... \
    -object 'authz-simple,id=auth0,identity=CN=laptop.example.com,,O=Example Org,,L=London,,ST=London,,C=GB' \
    ...

Note the use of quotes due to the x509 distinguished name containing whitespace, and escaping of ','. See? I told you. 😌

-object authz-listfile,id=id,filename=path,refresh=on|off — makes an authorization object that will control access to network services. Same vibe, different flavor. ✨

The filename parameter is the fully qualified path to a file containing the access control list rules in JSON format.

An example set of rules that match against SASL usernames might look like:

{
  "rules": [
     { "match": "fred", "policy": "allow", "format": "exact" },
     { "match": "bob", "policy": "allow", "format": "exact" },
     { "match": "danb", "policy": "deny", "format": "glob" },
     { "match": "dan*", "policy": "allow", "format": "exact" },
  ],
  "policy": "deny"
}

When checking access the object will iterate over all the rules and the first rule to match will have its policy value returned as the result. If no rules match, then the default policy value is returned.

The rules can either be an exact string match, or they can use the simple UNIX glob pattern matching to allow wildcards to be used. 🦋

If refresh is set to true the file will be monitored and automatically reloaded whenever its content changes. Iconic, honestly.

As with the authz-simple object, the format of the identity strings being matched depends on the network service, but is usually a TLS x509 distinguished name, or a SASL username.

An example authorization object to validate a SASL username would look like:

# qemu-system-x86_64 \
    ... \
    -object authz-simple,id=auth0,filename=/etc/qemu/vnc-sasl.acl,refresh=on \
    ...

-object authz-pam,id=id,service=string — makes an authorization object that will control access to network services. Third one, we're collecting them like stickers. 🎀

The service parameter provides the name of a PAM service to use for authorization. It requires that a file /etc/pam.d/service exist to provide the configuration for the account subsystem. So like, it needs a buddy file or it's not happening.

An example authorization object to validate a TLS x509 distinguished name would look like:

# qemu-system-x86_64 \
    ... \
    -object authz-pam,id=auth0,service=qemu-vnc \
    ...

There would then be a corresponding config file for PAM at /etc/pam.d/qemu-vnc that contains:

account requisite  pam_listfile.so item=user sense=allow \
           file=/etc/qemu/vnc.allow

Finally the /etc/qemu/vnc.allow file would contain the list of x509 distinguished names that are permitted access:

CN=laptop.example.com,O=Example Home,L=London,ST=London,C=GB

-object iothread,id=id,poll-max-ns=poll-max-ns,poll-grow=poll-grow,poll-shrink=poll-shrink,aio-max-batch=aio-max-batch — Creates a dedicated event loop thread that devices can be assigned to. This is known as an IOThread. 🧵

By default device emulation happens in vCPU threads or the main event loop thread. This can become a scalability bottleneck. IOThreads allow device emulation and I/O to run on other host CPUs. So basically: main character energy for your I/O, off the main thread. 👑

The id parameter is a unique ID that will be used to reference this IOThread from -device ...,iothread=id. Multiple devices can be assigned to an IOThread. Note that not all devices support an iothread parameter. Read that again. Not all of them. 😬

The query-iothreads QMP command lists IOThreads and reports their thread IDs so that the user can configure host CPU pinning/affinity.

IOThreads use an adaptive polling algorithm to reduce event loop latency. Instead of entering a blocking system call to monitor file descriptors and then pay the cost of being woken up when an event occurs, the polling algorithm spins waiting for events for a short time. The algorithm's default parameters are suitable for many cases but can be adjusted based on knowledge of the workload and/or host device latency.

The poll-max-ns parameter is the maximum number of nanoseconds to busy wait for events. Polling can be disabled by setting this value to 0. 🚫

The poll-grow parameter is the multiplier used to increase the polling time when the algorithm detects it is missing events due to not polling long enough.

The poll-shrink parameter is the divisor used to decrease the polling time when the algorithm detects it is spending too long polling without encountering events.

The aio-max-batch parameter is the maximum number of requests in a batch for the AIO engine, 0 means that the engine will use its default.

The IOThread parameters can be modified at run-time using the qom-set command (where iothread1 is the IOThread's id):

(qemu) qom-set /objects/iothread1 poll-max-ns 100000

During the graphical emulation, you can use special key combinations from the following table to change modes. By default the modifier is Ctrl+Alt (used in the table below) which can be changed with -display suboption mod= where appropriate. For example, -display sdl, grab-mod=lshift-lctrl-lalt changes the modifier key to Ctrl+Alt+Shift, while -display sdl,grab-mod=rctrl changes it to the right Ctrl key. Keyboard shortcuts but make it fashion. 💅⌨️

🎀 Multiplexer Keys 🎀

okay so when you're in the graphics window, these key combos are your lil remote control 💖

Ctrl+Alt+f — toggle full screen. yes bestie, go big mode 🖥️✨
Ctrl+Alt++ — enlarge the screen, zoom zoom 🔍
Ctrl+Alt+- — shrink the screen, back it up 🫸
Ctrl+Alt+0 — restore the screen's un-scaled dimensions, i.e. snap it back to normal, no cap
Ctrl+Alt+n — switch to virtual console n. the standard console mappings are literally these:
- 1: Target system display 👑
- 2: Monitor 🌸
- 3: Serial port 🦋
Ctrl+Alt+g — toggle mouse and keyboard grab. it's giving "who gets to control the cursor" energy 💅

in the virtual consoles, you can use Ctrl+Up, Ctrl+Down, Ctrl+PageUp and Ctrl+PageDown to move in the back log 📜 (scroll back through history, iconic behaviour fr fr)

During emulation, if you are using a character backend multiplexer (which is the default if you are using -nographic) then several commands are available via an escape sequence. These key sequences all start with an escape character, which is Ctrl+a by default, but can be changed with -echr. The list below assumes you're using the default. ✨

🌈 Multiplexer Keys 🌈

Ctrl+a h — print this help, your own personal cheat sheet 🫶
Ctrl+a x — exit emulator. bye bestie 😭
Ctrl+a s — save disk data back to file (if -snapshot) 💾
Ctrl+a t — toggle console timestamps ⏰
Ctrl+a b — send break (magic sysrq in Linux) 🪄
Ctrl+a c — rotate between the frontends connected to the multiplexer (usually this switches between the monitor and the console) 🔄
Ctrl+a Ctrl+a — send the escape character to the frontend 💫

lowkey the Ctrl+a Ctrl+a one is the "escape the escape" move, and honestly? main character energy 🎀

📝 NOTES 📝

okay so bestie, plot twist incoming: it's not just regular file images for your emulated storage devices 💾 — QEMU can also vibe with networked resources like iSCSI devices. Those get specified with a special URL syntax. And that's on periodt. 💅

🔌 iSCSI

iSCSI support lets QEMU hit up iSCSI resources directly and use them as images for the guest storage. Both disk and cdrom images are supported, no cap. 🫶

Syntax for specifying iSCSI LUNs is

"iscsi://<target-ip>[:<port>]/<target-iqn>/<lun>"

By default qemu will use the iSCSI initiator-name 'iqn.2008-11.org.linux-kvm[:<name>]' but this can also be set from the command line or a configuration file.

Since version QEMU 2.4 it is possible to specify a iSCSI request timeout to detect stalled requests and force a reestablishment of the session. The timeout is specified in seconds. The default is 0 which means no timeout. Libiscsi 1.15.0 or greater is required for this feature.

Example (without authentication):

qemu-system-x86_64 -iscsi initiator-name=iqn.2001-04.com.example:my-initiator \
                 -cdrom iscsi://192.0.2.1/iqn.2001-04.com.example/2 \
                 -drive file=iscsi://192.0.2.1/iqn.2001-04.com.example/1

Example (CHAP username/password via URL):

qemu-system-x86_64 -drive file=iscsi:<//user%password@192.0.2.1/iqn.2001-04.com.example/1>

Example (CHAP username/password via environment variables):

LIBISCSI_CHAP_USERNAME="user" \
LIBISCSI_CHAP_PASSWORD="password" \
qemu-system-x86_64 -drive file=iscsi://192.0.2.1/iqn.2001-04.com.example/1

🌐 NBD

QEMU supports NBD (Network Block Devices) both using TCP protocol as well as Unix Domain Sockets. With TCP, the default port is 10809. ✨

Syntax for specifying a NBD device using TCP, in preferred URI form:

"nbd://<server-ip>[:<port>]/[<export>]"

Syntax for specifying a NBD device using Unix Domain Sockets; remember that '?' is a shell glob character and may need quoting:

"nbd+unix:///[<export>]?socket=<domain-socket>"

Older syntax that is also recognized:

"nbd:<server-ip>:<port>[:exportname=<export>]"

Syntax for specifying a NBD device using Unix Domain Sockets

"nbd:unix:<domain-socket>[:exportname=<export>]"

Example for TCP

qemu-system-x86_64 --drive file=nbd:192.0.2.1:30000

Example for Unix Domain Sockets

qemu-system-x86_64 --drive file=nbd:unix:/tmp/nbd-socket

🔐 SSH

QEMU supports SSH (Secure Shell) access to remote disks. iconic behavior honestly 🔥

Examples:

qemu-system-x86_64 -drive file=ssh:<//user@host/path/to/disk.img>
qemu-system-x86_64 -drive file.driver=ssh,file.user=user,file.host=host,file.port=22,file.path=/path/to/disk.img

Currently authentication must be done using ssh-agent. Other authentication methods may be supported in future.

🫙 GlusterFS

GlusterFS is a user space distributed file system. QEMU supports the use of GlusterFS volumes for hosting VM disk images using TCP and Unix Domain Sockets transport protocols.

Syntax for specifying a VM disk image on GlusterFS volume is

URI:
gluster[+type]://[host[:port]]/volume/path[?socket=...][,debug=N][,logfile=...]

JSON:
'json:{"driver":"qcow2","file":{"driver":"gluster","volume":"testvol","path":"a.img","debug":N,"logfile":"...",
                                 "server":[{"type":"tcp","host":"...","port":"..."},
                                           {"type":"unix","socket":"..."}]}}'

Example

URI:
qemu-system-x86_64 --drive file=gluster://192.0.2.1/testvol/a.img,
                               file.debug=9,file.logfile=/var/log/qemu-gluster.log

JSON:
qemu-system-x86_64 'json:{"driver":"qcow2",
                          "file":{"driver":"gluster",
                                   "volume":"testvol","path":"a.img",
                                   "debug":9,"logfile":"/var/log/qemu-gluster.log",
                                   "server":[{"type":"tcp","host":"1.2.3.4","port":24007},
                                             {"type":"unix","socket":"/var/run/glusterd.socket"}]}}'
qemu-system-x86_64 -drive driver=qcow2,file.driver=gluster,file.volume=testvol,file.path=/path/a.img,
                                      file.debug=9,file.logfile=/var/log/qemu-gluster.log,
                                      file.server.0.type=tcp,file.server.0.host=1.2.3.4,file.server.0.port=24007,
                                      file.server.1.type=unix,file.server.1.socket=/var/run/glusterd.socket

🌍 HTTP/HTTPS/FTP/FTPS

QEMU supports read-only access to files accessed over http(s) and ftp(s). 👑

Syntax using a single filename:

<protocol>://[<username>[:<password>]@]<host>/<path>

where:

protocol — 'http', 'https', 'ftp', or 'ftps'.
username — Optional username for authentication to the remote server.
password — Optional password for authentication to the remote server.
host — Address of the remote server.
path — Path on the remote server, including any query string.

The following options are also supported:

url — The full URL when passing options to the driver explicitly.
readahead — The amount of data to read ahead with each range request to the remote server. This value may optionally have the suffix 'T', 'G', 'M', 'K', 'k' or 'b'. If it does not have a suffix, it will be assumed to be in bytes. The value must be a multiple of 512 bytes. It defaults to 256k.
sslverify — Whether to verify the remote server's certificate when connecting over SSL. It can have the value 'on' or 'off'. It defaults to 'on'.
cookie — Send this cookie (it can also be a list of cookies separated by ';') with each outgoing request. Only supported when using protocols such as HTTP which support cookies, otherwise ignored.
timeout — Set the timeout in seconds of the CURL connection. This timeout is the time that CURL waits for a response from the remote server to get the size of the image to be downloaded. If not set, the default timeout of 5 seconds is used.

Note that when passing options to qemu explicitly, driver is the value of <protocol>.

Example: boot from a remote Fedora 20 live ISO image

qemu-system-x86_64 --drive media=cdrom,file=https://archives.fedoraproject.org/pub/archive/fedora/linux/releases/20/Live/x86_64/Fedora-Live-Desktop-x86_64-20-1.iso,readonly

qemu-system-x86_64 --drive media=cdrom,file.driver=http,file.url=http://archives.fedoraproject.org/pub/fedora/linux/releases/20/Live/x86_64/Fedora-Live-Desktop-x86_64-20-1.iso,readonly

Example: boot from a remote Fedora 20 cloud image using a local overlay for writes, copy-on-read, and a readahead of 64k

qemu-img create -f qcow2 -o backing_file='json:{"file.driver":"http",, "file.url":"<http://archives.fedoraproject.org/pub/archive/fedora/linux/releases/20/Images/x86_64/Fedora-x86_64-20-20131211.1-sda.qcow2>",, "file.readahead":"64k"}' /tmp/Fedora-x86_64-20-20131211.1-sda.qcow2

qemu-system-x86_64 -drive file=/tmp/Fedora-x86_64-20-20131211.1-sda.qcow2,copy-on-read=on

Example: boot from an image stored on a VMware vSphere server with a self-signed certificate using a local overlay for writes, a readahead of 64k and a timeout of 10 seconds.

qemu-img create -f qcow2 -o backing_file='json:{"file.driver":"https",, "file.url":"<https://user:password@vsphere.example.com/folder/test/test-flat.vmdk?dcPath=Datacenter&dsName=datastore1>",, "file.sslverify":"off",, "file.readahead":"64k",, "file.timeout":10}' /tmp/test.qcow2

qemu-system-x86_64 -drive file=/tmp/test.qcow2

👀 SEE ALSO 👀

The HTML documentation of QEMU for more precise information and Linux user mode emulator invocation.

✍️ Author ✍️

Fabrice Bellard

📜 Copyright 📜

2025, The QEMU Project Developers

and that's a wrap bestie!! 💖 this was QEMU 10.2.1, dated Mar 27, 2026, and you ate the whole page. go forth and virtualize slayfully ✨💅🎀🦋 no cap, ily, bye!! 🫶

📦 where this page comes from

ubuntu resolute: qemu-system-x86 1:10.2.1+ds-1ubuntu3
ubuntu resolute: qemu-system-x86-hwe 1:10.2.1+ds-1ubuntu4
💖 girlified by deepseek-ai/DeepSeek-V4.1-Flash on 2026-10-13: a language model's rewrite of the original, under its terms

QEMU(1)

✨ NAME ✨

🦋 SYNOPSIS 🦋

🌸 DESCRIPTION 🌸

🎀 Machine-specific options 🎀

✨ OPTIONS ✨

🌈 Standard options 🌈

🌸 -add-fd fd=fd,set=set[,opaque=opaque] 🌸

✨ -set group.id.arg=value ✨

💖 -global driver.prop=value 💖

💖 -global driver=driver,property=property,value=value 💖

🦋 -boot 🦋

💜 -m [size=]megs[,slots=n,maxmem=size] 💜

🎧 AUDIO STUFF (still -audio-adjacent, iykyk) 🎧

🔌 DEVICES 🔌

🔌 -device ipmi-bmc-extern,id=id,chardev=id[,slave_addr=val] 🔌

🎀 -device isa-ipmi-kcs,bmc=id[,ioport=val][,irq=val] 🎀

💜 -device isa-ipmi-bt,bmc=id[,ioport=val][,irq=val] 💜

⭐ -device pci-ipmi-kcs,bmc=id` ⭐

🌸 -device pci-ipmi-bt,bmc=id` 🌸

👑 -device intel-iommu[,option=...] 👑

🦋 -device virtio-iommu-pci[,option=...] 🦋

💖 -device arm-smmuv3,primary-bus=id` 💖

🌈 -device amd-iommu[,option=...] 🌈

💅 -name name` 💅

🌟 -uuid uuid` 🌟

🍓 Block device options 🍓

💾 -fda file` 💾

💾 -fdb file` 💾

💜 -hda file` 💜

💜 -hdb file` 💜

💜 -hdc file` 💜

💜 -hdd file` 💜

🎀 -cdrom file` 🎀

⭐ -blockdev option[,option[,option[,...]]] ⭐

🌸 Driver-specific options for file 🌸

✨ Driver-specific options for raw ✨

👑 Driver-specific options for qcow2 👑

🦋 Driver-specific options for other drivers 🦋

🔥 -drive option[,option[,option[,...]]] 🔥

🌸 -mtdblock file 🌸

🎀 -sd file 🎀

🦋 -snapshot 🦋

✨ -fsdev ✨

-device virtio-9p-type,fsdev=id,mount_tag=mount_tag 💖

-virtfs local,path=path,mount_tag=mount_tag,security_model=security_model[,writeout=writeout][,readonly=on][,fmode=fmode][,dmode=dmode][,multidevs=multidevs]

-virtfs synth,mount_tag=mount_tag

✨ USB convenience options ✨

-usb

-usbdevice devname

🌸 Display options 🌸

-display type

-nographic</p> 🙈

-spice option[,option[,...]] 🌶️

-vga type 🎨

-full-screen 🖥️✨

🌈 i386 target only 🌈

🌐 Network options 🌐

OPTIONS (cont.) — the netdev era 🕸️

-netdev 🛠️

-netdev vde

-netdev af-xdp

-netdev vhost-user

-netdev vhost-vdpa

-netdev hubport

-net nic

-net user|passt|tap|bridge|socket|l2tpv3|vde

🎀 Character device options 🎀

🕳️ -chardev null,id=id

🧦 -chardev socket,id=id[,TCP options or unix options][,server=on|off][,wait=on|off][,telnet=on|off][,websocket=on|off][,reconnect-ms=milliseconds][,tls-creds=id][,tls-authz=id]

🐟 TCP options

🐚 unix options

📡 -chardev udp,id=id[,host=host],port=port[,localaddr=localaddr][,localport=localport][,ipv4=on|off][,ipv6=on|off]

🐭 -chardev msmouse,id=id

🛞 -chardev hub,id=id,chardevs.0=id[,chardevs.N=id]

🖥️ -chardev vc,id=id[[,width=width][,height=height]][[,cols=cols][,rows=rows]]

💍 -chardev ringbuf,id=id[,size=size]

📄 -chardev file,id=id,path=path[,input-path=input-path]

🚰 -chardev pipe,id=id,path=path

🪟 -chardev console,id=id

🌸 `-add-fd fd=fd,set=set[,opaque=opaque]` 🌸

✨ `-set group.id.arg=value` ✨

💖 `-global driver.prop=value` 💖

💖 `-global driver=driver,property=property,value=value` 💖

🦋 `-boot` 🦋

💜 `-m [size=]megs[,slots=n,maxmem=size]` 💜

🎧 AUDIO STUFF (still `-audio`-adjacent, iykyk) 🎧

🔌 `-device ipmi-bmc-extern,id=`id`,chardev=`id`[,slave_addr=`val`]` 🔌

🎀 `-device isa-ipmi-kcs,bmc=`id`[,ioport=`val`][,irq=`val`]` 🎀

💜 `-device isa-ipmi-bt,bmc=`id`[,ioport=`val`][,irq=`val`]` 💜

⭐ `-device pci-ipmi-kcs,bmc=`id` ⭐

🌸 `-device pci-ipmi-bt,bmc=`id` 🌸

👑 `-device intel-iommu[,option=...]` 👑

🦋 `-device virtio-iommu-pci[,option=...]` 🦋

💖 `-device arm-smmuv3,primary-bus=`id` 💖

🌈 `-device amd-iommu[,option=...]` 🌈

💅 `-name` name` 💅

🌟 `-uuid` uuid` 🌟

💾 `-fda` file` 💾

💾 `-fdb` file` 💾

💜 `-hda` file` 💜

💜 `-hdb` file` 💜

💜 `-hdc` file` 💜

💜 `-hdd` file` 💜

🎀 `-cdrom` file` 🎀

⭐ `-blockdev` option`[,`option`[,`option`[,...]]]` ⭐

🌸 Driver-specific options for `file` 🌸

✨ Driver-specific options for `raw` ✨

👑 Driver-specific options for `qcow2` 👑

🔥 `-drive option[,option[,option[,...]]]` 🔥

🌸 `-mtdblock` file 🌸

🎀 `-sd` file 🎀

🦋 `-snapshot` 🦋

✨ `-fsdev` ✨

`-device virtio-9p-type,fsdev=id,mount_tag=mount_tag` 💖

`-virtfs local,path=path,mount_tag=mount_tag,security_model=security_model[,writeout=writeout][,readonly=on][,fmode=fmode][,dmode=dmode][,multidevs=multidevs]`

`-virtfs synth,mount_tag=mount_tag`

`-usb`

`-usbdevice devname`

`-display type`

`-netdev` 🛠️

🕳️ `-chardev null,id=id`

🧦 `-chardev socket,id=id[,TCP options or unix options][,server=on|off][,wait=on|off][,telnet=on|off][,websocket=on|off][,reconnect-ms=milliseconds][,tls-creds=id][,tls-authz=id]`

📡 `-chardev udp,id=id[,host=host],port=port[,localaddr=localaddr][,localport=localport][,ipv4=on|off][,ipv6=on|off]`

🐭 `-chardev msmouse,id=id`

🛞 `-chardev hub,id=id,chardevs.0=id[,chardevs.N=id]`

🖥️ `-chardev vc,id=id[[,width=width][,height=height]][[,cols=cols][,rows=rows]]`

💍 `-chardev ringbuf,id=id[,size=size]`

📄 `-chardev file,id=id,path=path[,input-path=input-path]`

🚰 `-chardev pipe,id=id,path=path`

🪟 `-chardev console,id=id`

🔌 `-chardev serial,id=id,path=path`

🎀 `-chardev pty,id=id[,path=path]`

🫶 `-chardev stdio,id=id[,signal=on|off]`

🌸 `-object tls-cipher-suites,id=id,priority=priority` 🌸

🦋 `-object filter-buffer,id=id,netdev=netdevid,interval=t[,queue=all|rx|tx][,status=on|off][,position=head|tail|id=<id>][,insert=behind|before]` 🦋

💖 `-object filter-mirror,id=id,netdev=netdevid,outdev=chardevid,queue=all|rx|tx[,vnet_hdr_support][,position=head|tail|id=<id>][,insert=behind|before]` 💖

🎀 `-object filter-redirector,id=id,netdev=netdevid,indev=chardevid,outdev=chardevid,queue=all|rx|tx[,vnet_hdr_support][,position=head|tail|id=<id>][,insert=behind|before]` 🎀

🌈 `-object filter-rewriter,id=id,netdev=netdevid,queue=all|rx|tx,[vnet_hdr_support][,position=head|tail|id=<id>][,insert=behind|before]` 🌈

🍓 `-object filter-dump,id=id,netdev=dev[,file=filename][,maxlen=len][,position=head|tail|id=<id>][,insert=behind|before]` 🍓

👑 `-object colo-compare,id=id,primary_in=chardevid,secondary_in=chardevid,outdev=chardevid,iothread=id[,vnet_hdr_support][,notify_dev=id][,compare_timeout=@var{ms}][,expired_scan_cycle=@var{ms}][,max_queue_size=@var{size}]` 👑