Config...ketUnit(3pm)

📦

version 0.260.1 · 6 versions

0.260.1 · ubuntu stonking (latest)
0.249.1 · ubuntu jammy
0.254.1 · ubuntu noble
0.252.2 · debian bookworm
0.258.1 · ubuntu resolute
0.257.2 · debian trixie, ubuntu questing

so the header on this one reads Config...ketUnit(3pm) over on the left, User Contributed Perl Documentation on the right, and then Config...ketUnit(3pm) again, because Perl docs love a lil encore 💅

✨ NAME ✨

Config::Model::models::Systemd::Section::SocketUnit — it's the Configuration class for Systemd::Section::SocketUnit. no cap, that's the whole name, it's giving very-many-colons but we move 💖

🌸 DESCRIPTION 🌸

These are Configuration classes used by Config::Model. that's it. that's the vibe. ✨

🎀 Elements 🎀

💜 Description

A brief, meaningful, human-readable text identifying the unit, bestie. systemd (and any suitable UIs out there) might use this as a user-visible label for the unit, so this string should identify the unit rather than just describe it — yes, even though the name of the field is literally "Description", okay? 😭 It also should not just repeat the unit name. Good examples that ate: "Apache HTTP Server" or "Postfix Mail Server". Bad examples, do not do this: "high-performance lightweight HTTP server" (way too generic, giving nothing) or "Apache" (meaningless for people who don't know the Apache HTTP server project, plus it duplicates the unit name 🙈).

systemd may use this string as a noun in status messages — like "Starting Description...", "Started Description.", "Reached target Description.", "Failed to start Description." — so it should be capitalized, and it should not be a full sentence, or a phrase with a verb conjugated in the present continuous, or end in a full stop. Bad examples include "exiting the container", "updating the database once per day.", or "OpenSSH server second instance daemon". 💀

Optional. Type uniline.

📚 Documentation

A space-separated list of URIs referencing documentation for this unit or its configuration. Accepted are only URIs of the types "http://", "https://", "file:", "info:", "man:". For more information about the syntax of these URIs, see uri(7). 📖

The URIs should be listed in order of relevance, starting with the most relevant. It is a good idea to first reference documentation that explains what the unit's purpose is, followed by how it is configured, followed by any other related documentation. Obsessed with a well-ordered list, honestly. 💅

This option may be specified more than once, in which case the specified list of URIs is merged. If the empty string is assigned to this option, the list is reset and all prior assignments will have no effect. Optional. Type list of uniline.

💖 Wants

Configures (weak) requirement dependencies on other units. This option may be specified more than once, or multiple space-separated units may be specified in one option — in which case dependencies for all listed names will be created. Dependencies of this type may also be configured outside of the unit configuration file by adding a symlink to a .wants/ directory accompanying the unit file. For details, see above.

Units listed in this option will be started if the configuring unit is. However, if the listed units fail to start or cannot be added to the transaction, this has no impact on the validity of the transaction as a whole, and this unit will still be started. This is the recommended way to hook the start-up of one unit to the start-up of another unit. ✨

Note that requirement dependencies do not influence the order in which services are started or stopped. That has to be configured independently with the "After" or "Before" options. If unit "foo.service" pulls in unit "bar.service" as configured with "Wants" and no ordering is configured with "After" or "Before", then both units will be started simultaneously and without any delay between them if "foo.service" is activated. 😳

Optional. Type list of uniline.

🔥 Requires

Similar to "Wants", but declares a stronger requirement dependency. Dependencies of this type may also be configured by adding a symlink to a .requires/ directory accompanying the unit file.

If this unit gets activated, the units listed will be activated as well. If one of the other units fails to activate, and an ordering dependency "After" on the failing unit is set, this unit will not be started. Besides, with or without specifying "After", this unit will be stopped (or restarted) if one of the other units is explicitly stopped (or restarted).

Often, it is a better choice to use "Wants" instead of "Requires" in order to achieve a system that is more robust when dealing with failing services. ngl, that's a whole life lesson. 🫶

Note that this dependency type does not imply that the other unit always has to be in active state when this unit is running. Specifically: failing condition checks (such as "ConditionPathExists", "ConditionPathIsSymbolicLink", … — see below) do not cause the start job of a unit with a "Requires" dependency on it to fail. Also, some unit types may deactivate on their own (for example, a service process may decide to exit cleanly, or a device may be unplugged by the user), which is not propagated to units having a "Requires" dependency. Use the "BindsTo" dependency type together with "After" to ensure that a unit may never be in active state without a specific other unit also in active state (see below).

Optional. Type list of uniline.

👑

💀 Requisite

Similar to "Requires". However, if the units listed here are not started already, they will not be started and the starting of this unit will fail immediately. "Requisite" does not imply an ordering dependency, even if both units are started in the same transaction. Hence this setting should usually be combined with "After", to ensure this unit is not started before the other unit. it's giving "no prerequisites, no entry" 🙈

When "Requisite=b.service" is used on "a.service", this dependency will show as "RequisiteOf=a.service" in property listing of "b.service". "RequisiteOf" dependency cannot be specified directly.

Optional. Type list of uniline.

🌈 BindsTo

Configures requirement dependencies, very similar in style to "Requires". However, this dependency type is stronger: in addition to the effects of "Requires", which already stops (or restarts) the configuring unit when a listed unit is explicitly stopped (or restarted), it also does so when a listed unit stops unexpectedly (which includes when it fails). 😭

Units can suddenly, unexpectedly enter inactive state for different reasons: the main process of a service unit might terminate on its own choice, the backing device of a device unit might be unplugged, or the mount point of a mount unit might be unmounted without involvement of the system and service manager. chaos, honestly.

When used in conjunction with "After" on the same unit the behaviour of "BindsTo" is even stronger. In this case, the unit bound to strictly has to be in active state for this unit to also be in active state. This not only means a unit bound to another unit that suddenly enters inactive state, but also one that is bound to another unit that gets skipped due to an unmet condition check (such as "ConditionPathExists", "ConditionPathIsSymbolicLink", … — see below) will be stopped, should it be running. Hence, in many cases it is best to combine "BindsTo" with "After". 💅

When "BindsTo=b.service" is used on "a.service", this dependency will show as "BoundBy=a.service" in property listing of "b.service". "BoundBy" dependency cannot be specified directly.

Optional. Type list of uniline.

🦋 PartOf

Configures dependencies similar to "Requires", but limited to stopping and restarting of units. When systemd stops or restarts the units listed here, the action is propagated to this unit. Note that this is a one-way dependency — changes to this unit do not affect the listed units. periodt. 💅

When "PartOf=b.service" is used on "a.service", this dependency will show as "ConsistsOf=a.service" in property listing of "b.service". "ConsistsOf" dependency cannot be specified directly.

Optional. Type list of uniline.

🌟 Upholds

Configures dependencies similar to "Wants", but as long as this unit is up, all units listed in "Upholds" are started whenever found to be inactive or failed, and no job is queued for them. While a "Wants" dependency on another unit has a one-time effect when this unit is started, a "Upholds" dependency on it has a continuous effect, constantly restarting the unit if necessary. Obsessed — it never stops showing up for you. 🫶

This is an alternative to the "Restart" setting of service units, to ensure they are kept running whatever happens. The restart happens without delay, and usual per-unit rate-limit applies.

When "Upholds=b.service" is used on "a.service", this dependency will show as "UpheldBy=a.service" in the property listing of "b.service".

Optional. Type uniline.

⚔️ Conflicts

A space-separated list of unit names. Configures negative requirement dependencies. If a unit has a "Conflicts" requirement on a set of other units, then starting it will stop all of them and starting any of them will stop it. it's giving enemies to enemies 😤

Note that this setting does not imply an ordering dependency, similarly to the "Wants" and "Requires" dependencies described above. This means that to ensure that the conflicting unit is stopped before the other unit is started, an "After" or "Before" dependency must be declared. It does not matter which of the two ordering dependencies is used, because stop jobs are always ordered before start jobs, see the discussion in "Before"/"After" below.

If unit A that conflicts with unit B is scheduled to be started at the same time as B, the transaction will either fail (in case both are required parts of the transaction) or be modified to be fixed (in case one or both jobs are not a required part of the transaction). In the latter case, the job that is not required will be removed, or in case both are not required, the unit that conflicts will be started and the unit that is conflicted is stopped. 💀

Optional. Type list of uniline.

⏳ Before

These two settings expect a space-separated list of unit names. They may be specified more than once, in which case dependencies for all listed names are created.

Those two settings configure ordering dependencies between units. If unit "foo.service" contains the setting "Before=bar.service" and both units are being started, "bar.service"'s start-up is delayed until "foo.service" has finished starting up. "After" is the inverse of "Before", i.e. while "Before" ensures that the configured unit is started before the listed unit begins starting up, "After" ensures the opposite, that the listed unit is fully started up before the configured unit is started.

bestie this is only part 1 of 8, do not close the tab, there's so much more coming 💖

When two units that have an ordering thing going on between them both get shut down, bestie, the start-up order gets flipped. 🔄 Like, the inverse. So if a unit is set up with After pointing at another one, the first one gets stopped before the second one when they're both going down.

Now here's the glow-up detail: if you've got two units with any ordering dependency between them, and one gets shut down while the other gets started up, the shutdown is always ordered before the start-up. Doesn't matter if the dependency is After or Before — nope, irrelevant here. Also doesn't matter which of the two is the one being shut down, as long as one is stopping and the other is starting; shutdown goes first in every single case. ✨

And if two units have no ordering dependency at all? They just get shut down or started up at the same time. No ordering happens. Periodt.

When exactly a unit is "done starting up" depends on the unit type — different vibes for different types. Most importantly 👑: for service units, start-up is considered complete (for the purposes of Before/After) when all its configured start-up commands have been invoked and they either failed or reported start-up success. Heads up, this includes ExecStartPost (or ExecStopPost for the shutdown case). 💅

Ok important caveat so you don't get confused: those settings are independent of and orthogonal to the requirement dependencies you set with Requires, Wants, Requisite, or BindsTo. A super common pattern is putting the same unit name in both After and Wants, in which case the listed unit gets started before the unit that has these options configured. 🫶

And one more thing, and this is a real one: Before dependencies on device units have no effect and are not supported. 🚫 Devices generally show up because of an external hotplug event, and systemd creates the matching device unit without delay. Optional. Type list of uniline.

After ✨

These two settings expect a space-separated list of unit names. You can specify them more than once, and if you do, dependencies get created for all the listed names. 🎀

So these two settings configure ordering dependencies between units. Say unit foo.service contains Before=bar.service and both units are being started — then bar.service's start-up is delayed until foo.service has finished starting up. After is literally the inverse of Before: while Before makes sure the configured unit starts before the listed unit even begins starting, After makes sure the listed unit is fully started up before the configured unit starts. 🔥

When two units with an ordering dependency between them are shut down, the inverse of the start-up order is applied. I.e. if a unit is configured with After on another unit, the former is stopped before the latter if both are shut down. Given two units with any ordering dependency between them, if one unit is shut down and the other is started up, the shutdown is ordered before the start-up. It does not matter if the ordering dependency is After or Before, in this case. It also does not matter which of the two is shut down, as long as one is shut down and the other is started up; the shutdown is ordered before the start-up in all cases. If two units have no ordering dependencies between them, they are shut down or started up simultaneously, and no ordering takes place. It depends on the unit type when precisely a unit has finished starting up. Most importantly, for service units start-up is considered completed for the purpose of Before/After when all its configured start-up commands have been invoked and they either failed or reported start-up success. Note that this includes ExecStartPost (or ExecStopPost for the shutdown case). 🌸

Note that those settings are independent of and orthogonal to the requirement dependencies as configured by Requires, Wants, Requisite, or BindsTo. It is a common pattern to include a unit name in both the After and Wants options, in which case the unit listed will be started before the unit that is configured with these options. 💜

Note that Before dependencies on device units have no effect and are not supported. Devices generally become available as a result of an external hotplug event, and systemd creates the corresponding device unit without delay. Optional. Type list of uniline.

OnFailure 💀

A space-separated list of one or more units that get activated when this unit enters the failed state. Optional. Type uniline.

OnSuccess 👑

A space-separated list of one or more units that get activated when this unit enters the inactive state. Optional. Type uniline.

PropagatesReloadTo 🦋

A space-separated list of one or more units to which reload requests from this unit shall be propagated to, or units from which reload requests shall be propagated to this unit, respectively. Issuing a reload request on a unit will automatically also enqueue reload requests on all units that are linked to it using these two settings. Optional. Type uniline.

ReloadPropagatedFrom 🦋

PropagatesStopTo 🛑

A space-separated list of one or more units to which stop requests from this unit shall be propagated to, or units from which stop requests shall be propagated to this unit, respectively. Issuing a stop request on a unit will automatically also enqueue stop requests on all units that are linked to it using these two settings. Optional. Type uniline.

StopPropagatedFrom 🛑

JoinsNamespaceOf 🧚

For units that start processes (like service units), this lists one or more other units whose network and/or temporary file namespace to join. If you set this on a unit — say a.service has JoinsNamespaceOf=b.service — then the inverse dependency (JoinsNamespaceOf=a.service for b.service) is implied. ✨

This only applies to unit types that support the PrivateNetwork, NetworkNamespacePath, PrivateIPC, IPCNamespacePath, and PrivateTmp directives (peep systemd.exec(5) for the details). If a unit that has this setting set gets started, its processes will see the same /tmp/, /var/tmp/, IPC namespace and network namespace as one listed unit that is started. And if multiple listed units are already started and they don't share their namespace, then it is not defined which namespace gets joined. 😭

Note that this setting only has an effect if PrivateNetwork/NetworkNamespacePath, PrivateIPC/IPCNamespacePath and/or PrivateTmp is enabled for both the unit that joins the namespace and the unit whose namespace is joined. Optional. Type uniline.

RequiresMountsFor 🌈

Takes a space-separated list of absolute paths. Automatically adds dependencies of type Requires and After for all mount units required to access the specified path.

Mount points marked with noauto are not mounted automatically through local-fs.target, but are still honored for the purposes of this option, i.e. they will be pulled in by this unit. Optional. Type uniline.

WantsMountsFor 🌈

Same as RequiresMountsFor, but adds dependencies of type Wants instead of Requires. Optional. Type uniline.

OnSuccessJobMode ⭐

Takes a value of fail, replace, replace-irreversibly, isolate, flush, ignore-dependencies or ignore-requirements. OnFailureJobMode defaults to replace, OnSuccessJobMode defaults to fail. Specifies how the units listed in OnSuccess/OnFailure will be enqueued. See systemctl(1)'s --job-mode= option for details on the possible values. If this is set to isolate, only a single unit may be listed in OnSuccess/OnFailure. Optional. Type uniline.

OnFailureJobMode ⭐

Note: OnFailureJobMode is migrated with $unit and with: - $unit => "- OnFailureIsolate"

IgnoreOnIsolate 🙈

Takes a boolean argument. If true, this unit will not be stopped when isolating another unit. Defaults to false for service, target, socket, timer, and path units, and true for slice, scope, device, swap, mount, and automount units. Optional. Type boolean.

StopWhenUnneeded 🍓

Takes a boolean argument. If true, this unit will be stopped when it is no longer used. Note that, in order to minimize the work to be executed, systemd will not stop units by default unless they are conflicting with other units, or the user explicitly requested their shut down. If this option is set, a unit will be automatically cleaned up if no other active unit requires it. Defaults to false. Optional. Type boolean.

upstream_default value :
    no

RefuseManualStart 💅

Takes a boolean argument. If true, this unit can only be activated or deactivated indirectly. In this case, explicit start-up or termination requested by the user is denied, however if it is started or stopped as a dependency of another unit, start-up or termination will succeed. This is mostly a safety feature to ensure that the user does not accidentally activate units that are not intended to be activated explicitly, and not accidentally deactivate units that are not intended to be deactivated. These options default to false. Optional. Type boolean.

RefuseManualStop 💅

AllowIsolate 💅

Takes a boolean argument. If "true", this unit may be used with the systemctl isolate command. Otherwise, this will be refused. It probably is a good idea to leave this disabled except for target units that shall be used similar to runlevels in SysV init systems, just as a precaution to avoid unusable system states. This option defaults to "false". Optional. Type boolean.

DefaultDependencies 🎀

Takes a boolean argument. If "yes", (the default), a few default dependencies will implicitly be created for the unit. The actual dependencies created depend on the unit type. For example, for service units, these dependencies ensure that the service is started only after basic system initialization is completed and is properly terminated on system shutdown. See the respective man pages for details. Generally, only services involved with early boot or late shutdown should set this option to "no". It is highly recommended to leave this option enabled for the majority of common units. If set to "no", this option does not disable all implicit dependencies, just non-essential ones. Optional. Type boolean.

SurviveFinalKillSignal 🦋

Takes a boolean argument. Defaults to "no". If "yes", processes belonging to this unit will not be sent the final "SIGTERM" and "SIGKILL" signals during the final phase of the system shutdown process. This functionality replaces the older mechanism that allowed a program to set "argv[0][0] = '@'" as described at systemd and Storage Daemons for the Root File System <https://systemd.io/ROOT_STORAGE_DAEMONS>, which however continues to be supported. Optional. Type boolean.

upstream_default value : no

CollectMode 🧚

Tweaks the "garbage collection" algorithm for this unit. Takes one of "inactive" or "inactive-or-failed". If set to "inactive" the unit will be unloaded if it is in the "inactive" state and is not referenced by clients, jobs or other units — however it is not unloaded if it is in the "failed" state. In "failed" mode, failed units are not unloaded until the user invoked systemctl reset-failed on them to reset the "failed" state, or an equivalent command. This behaviour is altered if this option is set to "inactive-or-failed": in this case, the unit is unloaded even if the unit is in a "failed" state, and thus an explicitly resetting of the "failed" state is not necessary. Note that if this mode is used unit results (such as exit codes, exit signals, consumed resources, …) are flushed out immediately after the unit completed, except for what is stored in the logging subsystem. Defaults to "inactive". Optional. Type enum. choice: 'inactive', 'inactive-or-failed'.

FailureActionExitStatus 💜

Controls the exit status to propagate back to an invoking container manager (in case of a system service) or service manager (in case of a user manager) when the "FailureAction"/"SuccessAction" are set to "exit" or "exit-force" and the action is triggered. By default, the exit status of the main process of the triggering unit (if this applies) is propagated. Takes a value in the range 0…255 or the empty string to request default behaviour. Optional. Type uniline.

SuccessActionExitStatus ✨

JobTimeoutSec ⏳

"JobTimeoutSec" specifies a timeout for the whole job that starts running when the job is queued. "JobRunningTimeoutSec" specifies a timeout that starts running when the queued job is actually started. If either limit is reached, the job will be cancelled, the unit however will not change state or even enter the "failed" mode.

Both settings take a time span with the default unit of seconds, but other units may be specified, see systemd.time(7). The default is "infinity" (job timeouts disabled), except for device units where "JobRunningTimeoutSec" defaults to "DefaultDeviceTimeoutSec".

Note: these timeouts are independent from any unit-specific timeouts (for example, the timeout set with "TimeoutStartSec" in service units). The job timeout has no effect on the unit itself. Or in other words: unit-specific timeouts are useful to abort unit state changes, and revert them. The job timeout set with this option however is useful to abort only the job waiting for the unit state to change.

Optional. Type uniline.

JobRunningTimeoutSec 🌸

Note: these timeouts are independent from any unit-specific timeouts (for example, the timeout set with "TimeoutStartSec" in service units). The job timeout has no effect on the unit itself. Or in other words: unit-specific timeouts are useful to abort unit state changes, and revert them. The job timeout set with this option however is useful to abort only the job waiting for the unit state to change.

Optional. Type uniline.

JobTimeoutAction 🔥

"JobTimeoutAction" optionally configures an additional action to take when the timeout is hit, see description of "JobTimeoutSec" and "JobRunningTimeoutSec" above. It takes the same values as "FailureAction"/"SuccessAction". Defaults to "none".

"JobTimeoutRebootArgument" configures an optional reboot string to pass to the reboot(2) system call. Optional. Type uniline.

JobTimeoutRebootArgument 💥

"JobTimeoutRebootArgument" configures an optional reboot string to pass to the reboot(2) system call. Optional. Type uniline.

StartLimitAction 🚨

Configure an additional action to take if the rate limit configured with "StartLimitIntervalSec" and "StartLimitBurst" is hit. Takes the same values as the "FailureAction"/"SuccessAction" settings. If "none" is set, hitting the rate limit will trigger no action except that the start will not be permitted. Defaults to "none". Optional. Type enum. choice: 'exit', 'exit-force', 'halt', 'halt-force', 'halt-immediate', 'kexec', 'kexec-force', 'none', 'poweroff', 'poweroff-force', 'poweroff-immediate', 'reboot', 'reboot-force', 'reboot-immediate', 'soft-reboot', 'soft-reboot-force'.

SourcePath 🍓

A path to a configuration file this unit has been generated from. This is primarily useful for implementation of generator tools that convert configuration from an external configuration file format into native unit files. This functionality should not be used in normal units. Optional. Type uniline.

ConditionArchitecture 🏗️

Check whether the system is running on a specific architecture. Takes one of "x86", "x86-64", "ppc", "ppc-le", "ppc64", "ppc64-le", "ia64", "parisc", "parisc64", "s390", "s390x", "sparc", "sparc64", "mips", "mips-le", "mips64", "mips64-le", "alpha", "arm", "arm-be", "arm64", "arm64-be", "sh", "sh64", "m68k", "tilegx", "cris", "arc", "arc-be", or "native".

Use systemd-analyze(1) for the complete list of known architectures.

The architecture is determined from the information returned by uname(2) and is thus subject to personality(2). Note that a "Personality" setting in the same unit file has no effect on this condition. A special architecture name "native" is mapped to the architecture the system manager itself is compiled for. The test may be negated by prepending an exclamation mark. Optional. Type list of enum.

ConditionFirmware 🖥️

Check whether the system's firmware is of a certain type. The following values are possible: Optional. Type list of uniline.

ConditionVirtualization 👾

Check whether the system is executed in a virtualized environment and optionally test whether it is a specific implementation. Takes either boolean value to check if being executed in any virtualized environment, or one of "vm" and "container" to test against a generic type of virtualization solution, or one of "qemu", "kvm", "amazon", "zvm", "vmware", "microsoft", "oracle", "powervm", "xen", "bochs", "uml", "bhyve", "qnx", "apple", "sre", "openvz", "lxc", "lxc-libvirt", "systemd-nspawn", "docker", "podman", "rkt", "wsl", "proot", "pouch", "acrn" to test against a specific implementation, or "private-users" to check whether we are running in a user namespace. See systemd-detect-virt(1) for a full list of known virtualization technologies and their identifiers. If multiple virtualization technologies are nested, only the innermost is considered. The test may be negated by prepending an exclamation mark. Optional. Type list of uniline.

ConditionHost 🏠

"ConditionHost" may be used to match against the hostname, machine ID, boot ID or product UUID of the host. This either takes a hostname string (optionally with shell style globs) which is tested against the locally set hostname as returned by gethostname(2), or a 128bit ID or UUID, formatted as string. The latter is compared against machine ID, boot ID and the firmware product UUID if there is any. See machine-id(5) for details about the machine ID. The test may be negated by prepending an exclamation mark. Optional. Type list of uniline.

ConditionKernelCommandLine 🐧

"ConditionKernelCommandLine" may be used to check whether a specific kernel command line option is set (or if prefixed with the exclamation mark — unset). The argument must either be a single word, or an assignment (i.e. two words, separated by "="). In the former case the kernel command line is searched for the word appearing as is, or as left hand side of an assignment. In the latter case, the exact assignment is looked for with right and left hand side matching. This operates on the kernel command line communicated to userspace via "/proc/cmdline", except when the service manager is invoked as payload of a container manager, in which case the command line of PID 1 is used instead (i.e. "/proc/1/cmdline"). Optional. Type list of uniline.

ConditionKernelVersion

so ConditionKernelVersion is your little "hey does this kernel even" checker 💅 it looks at the kernel version (the thing uname -r spits out) and asks: does it match this expression, or (if you slap a ! in front) does it not match. The argument has to be a list of (potentially quoted) expressions, bestie — a whole list, not just one.

Each expression starts with one of these operators:

= or != — for string comparisons
<, <=, ==, <>, >=, > — for version comparisons
$=, !$= — for a shell-style glob match

and if you're feeling lazy and don't specify an operator at all, $= is implied. no cap.

okay but real talk ⚠️ using the kernel version string to figure out what features a kernel supports is unreliable. why? because literally everyone backports drivers, features and fixes from newer upstream kernels into older distro kernels. so this check is inherently unportable and you should not use it for units that might land on different distributions. 🙈

Optional. Type list of uniline.

ConditionVersion

ConditionVersion is the glow-up version of the above ✨ it checks whether a software version matches an expression, or doesn't match if you prefix it with !. The first argument is the software whose version you're checking — right now kernel, systemd and glibc are supported. Omit that first argument and kernel is implied, easy.

The second argument must be a list of (potentially quoted) expressions. Each one starts with:

= or != — string comparisons
<, <=, ==, <>, >=, > — version comparisons
$=, !$= — shell-style glob match

No operator? $= is implied, again. 👑

Optional. Type list of uniline.

ConditionCredential

ConditionCredential checks whether a credential with the name you give was passed into the service manager 🎀 the details live in the System and Service Credentials docs at https://systemd.io/CREDENTIALS.

in services for the system service manager → conditionalize services based on system credentials passed in
in services for the per-user service manager → conditionalize services based on credentials passed into the unit@.service service instance belonging to the user

The argument must be a valid credential name. Optional. Type list of uniline.

ConditionEnvironment

ConditionEnvironment vibe checks whether a specific environment variable is set (or, prefixed with !, unset) in the service manager's environment block 🌸 the argument can be:

a single word — checks if the variable with that name is defined in the environment block
an assignment (name=value) — checks if the variable with that exact value is defined

and here's the important bit, bestie: it's the service manager's own environment block being checked. not any variables defined with Environment or EnvironmentFile, mkay? this is especially useful when the service manager is running inside a containerized environment, or as a per-user service manager, because then you can check for variables passed in by the enclosing container manager or PAM. iconic behavior.

Optional. Type list of uniline.

ConditionSecurity

ConditionSecurity checks whether the given security technology is enabled on the system 🔥 currently, the following values are recognized:

The test may be negated by prepending an exclamation mark. Optional. Type list of uniline.

ConditionCapability

checks whether the given capability exists in the capability bounding set of the service manager 💀 and no, it does not check whether the capability is actually available in the permitted or effective sets — peep capabilities(7) for the deets. you pass a capability name like CAP_MKNOD, and you can prefix it with an exclamation mark to negate the check. Optional. Type list of uniline.

ConditionACPower

checks whether the system has AC power, or is exclusively battery powered, at the moment the unit gets activated 🔌 takes a boolean argument:

true → condition holds only if at least one AC connector of the system is connected to a power source, or if no AC connectors are known
false → condition holds only if there is at least one AC connector known and all AC connectors are disconnected from a power source

Optional. Type list of uniline.

ConditionNeedsUpdate

takes one of /var/ or /etc/ as its argument, possibly prefixed with a ! to invert the condition 🦋 this one lets you conditionalize units on whether that directory needs an update, because /usr/'s modification time is newer than the stamp file .updated in the directory you named.

super useful for offline updates of the vendor OS resources in /usr/ that require updating /etc/ or /var/ on the next boot. and heads up: units using this condition should order themselves before systemd-update-done.service(8) so they definitely run before the stamp file's modification time gets reset (which is what signals a completed update).

If the systemd.condition_needs_update= option is specified on the kernel command line (it takes a boolean), it will override the result of this condition check and takes precedence over any file modification time checks. And if that kernel command line option is used, systemd-update-done.service won't have immediate effect on any following ConditionNeedsUpdate checks until the system reboots without the kernel command line option specified anymore.

📌 quick notes so this scheme actually works:

the timestamp of /usr/ should be explicitly updated after its contents are modified. the kernel automatically updates modification timestamps on a directory only when immediate children of a directory are modified — modifying nested files will not automatically update the mtime of /usr/.
if your update method includes a call to execute the appropriate post-update steps itself, it should not touch the timestamp of /usr/. in a typical distribution packaging scheme, packages do any required update steps as part of installation or upgrade, so package contents are immediately usable. ConditionNeedsUpdate should be used with other update mechanisms, where that kind of immediate update doesn't happen.

Optional. Type list of enum.

ConditionFirstBoot

takes a boolean argument, and it conditionalizes units on whether the system is booting up for the first time 🎀 roughly meaning /etc/ was unpopulated when the system started booting (for details, see "First Boot Semantics" in machine-id(5)). First Boot is considered finished — so this condition evaluates as false — after the manager has finished the startup phase.

use it to populate /etc/ on the first boot after a factory reset, or when a new system instance boots up for the very first time. ✨

no cap, the service manager itself does setup steps during First Boot: it initializes machine-id(5) and presets all units, enabling or disabling them according to the systemd.preset(5) settings. additional setup can be done via units with ConditionFirstBoot=yes.

for robustness, units with ConditionFirstBoot=yes should order themselves before first-boot-complete.target and pull in this passive target with Wants. that way, if the first boot gets aborted, those units get re-run during the next system startup. 🫶

If the systemd.condition_first_boot= option is specified on the kernel command line (taking a boolean), it will override the result of this condition check, taking precedence over /etc/machine-id existence checks. Optional. Type list of boolean.

ConditionPathExists

checks for the existence of a file 🍓 if the specified absolute path name doesn't exist, the condition fails. and if the absolute path name you pass to ConditionPathExists is prefixed with an exclamation mark (!), the test is negated — so the unit is only started if the path does not exist. Optional. Type list of uniline.

ConditionPathExistsGlob

ConditionPathExistsGlob is like ConditionPathExists, but it checks for the existence of at least one file or directory matching the specified globbing pattern 🌈 Optional. Type list of uniline.

ConditionPathIsDirectory

ConditionPathIsDirectory is like ConditionPathExists but it verifies that a certain path exists and is a directory 📁 Optional. Type list of uniline.

ConditionPathIsSymbolicLink

ConditionPathIsSymbolicLink is like ConditionPathExists but it verifies that a certain path exists and is a symbolic link 🔗 Optional. Type list of uniline.

ConditionPathIsMountPoint

ConditionPathIsMountPoint is like ConditionPathExists but it verifies that a certain path exists and is a mount point 💽 Optional. Type list of uniline.

ConditionPathIsReadWrite

ConditionPathIsReadWrite is like ConditionPathExists but it verifies that the underlying file system is readable and writable — i.e. not mounted read-only ✍️ Optional. Type list of uniline.

ConditionPathIsEncrypted

ConditionPathIsEncrypted is like ConditionPathExists but it verifies that the underlying file system's backing block device is encrypted using dm-crypt/LUKS 🔐

⚠️ read this twice, bestie:

this check does not cover ext4 per-directory encryption — it only detects block level encryption
if the specified path resides on a file system on top of a loopback block device, only encryption above the loopback device is detected. whether the file system backing the loopback block device is encrypted is not detected.

Optional. Type list of uniline.

ConditionPathIsSocket

ConditionPathIsSocket is like ConditionPathExists but it verifies that a certain path exists and is a socket 🧦 Optional. Type list of uniline.

ConditionDirectoryNotEmpty

ConditionDirectoryNotEmpty is like ConditionPathExists but it verifies that a certain path exists and is a non-empty directory 📂 Optional. Type list of uniline.

ConditionFileNotEmpty

ConditionFileNotEmpty is like ConditionPathExists but it verifies that a certain path exists and refers to a regular file with a non-zero size 📄 Optional. Type list of uniline.

ConditionFileIsExecutable

ConditionFileIsExecutable is like ConditionPathExists but it verifies that a certain path exists, is a regular file, and is marked executable ⚡ Optional. Type list of uniline.

ConditionUser

ConditionUser takes a numeric UID, a UNIX user name, or the special value @system 👑 it checks whether the service manager is running as the given user. the special value @system checks if the user id is within the system user range.

💀 psst — this option is not useful for system services, because the system manager exclusively runs as the root user, so the test result is just constant. RIP.

Optional. Type list of uniline.

ConditionGroup

Bestie, this is ConditionUser's sibling 💅 — same energy, different check. It verifies that the service manager's real or effective group, or any of its auxiliary groups, matches the group or GID you named. And no, this one does not support the special value @system. Periodt.