ovn-northd(8)

📦
version 26.09.0 · 16 versions
, in fedora 44

NAME 👑

okay so this is the manual page for ovn-northd, the Open Virtual Network central control daemon. 💅

SYNOPSIS 🌈

ovn-northd [options]

DESCRIPTION 💖

ovn-northd is a centralized daemon, like the main character, responsible for translating the high-level OVN configuration into logical configuration consumable by daemons such as ovn-controller. It translates the logical network configuration in terms of conventional network concepts, taken from the OVN Northbound Database (see ovn-nb(5)), into logical datapath flows in the OVN Southbound Database (see ovn-sb(5)) below it. Periodt. ✨

OPTIONS ✨

  • --ovnnb-db=database — The OVSDB database containing the OVN Northbound Database. If the OVN_NB_DB environment variable is set, its value is used as the default. Otherwise, the default is unix:/ovnnb_db.sock. 💖
  • --ovnsb-db=database — The OVSDB database containing the OVN Southbound Database. If the OVN_SB_DB environment variable is set, its value is used as the default. Otherwise, the default is unix:/ovnsb_db.sock. 💖
  • --dry-run — Causes ovn-northd to start paused. In the paused state, ovn-northd does not apply any changes to the databases, although it continues to monitor them. For more information, see the pause command, under Runtime Management Commands below. 🛑
  • --n-threads=N — In certain situations, it may be desirable to enable parallelization on a system to decrease latency (at the potential cost of increasing CPU usage). This option will cause ovn-northd to use N threads when building logical flows, when N is within [2-256]. If N is 1, parallelization is disabled (default behavior). If N is less than 1, then N is set to 1, parallelization is disabled and a warning is logged. If N is more than 256, then N is set to 256, parallelization is enabled (with 256 threads) and a warning is logged. 🧵
  • --dump-inc-proc-graph[=node] — Dump the incremental processing engine graph representation in DOT format to stdout at startup and then exit. If node is specified, only the subgraph rooted at that engine node is printed. 📈

database in the above options must be an OVSDB active or passive connection method, as described in ovsdb(7).

Daemon Options 🎀

  • --pidfile[=pidfile] — Causes a file (by default, program.pid) to be created indicating the PID of the running process. If the pidfile argument is not specified, or if it does not begin with /, then it is created in .. If --pidfile is not specified, no pidfile is created. 📝
  • --overwrite-pidfile — By default, when --pidfile is specified and the specified pidfile already exists and is locked by a running process, the daemon refuses to start. Specify --overwrite-pidfile to cause it to instead overwrite the pidfile. When --pidfile is not specified, this option has no effect. 🔁
  • --detach — Runs this program as a background process. The process forks, and in the child it starts a new session, closes the standard file descriptors (which has the side effect of disabling logging to the console), and changes its current directory to the root (unless --no-chdir is specified). After the child completes its initialization, the parent exits. 👋
  • --monitor — Creates an additional process to monitor this program. If it dies due to a signal that indicates a programming error (SIGABRT, SIGALRM, SIGBUS, SIGFPE, SIGILL, SIGPIPE, SIGSEGV, SIGXCPU, or SIGXFSZ) then the monitor process starts a new copy of it. If the daemon dies or exits for another reason, the monitor process exits. This option is normally used with --detach, but it also functions without it. 👀
  • --no-chdir — By default, when --detach is specified, the daemon changes its current working directory to the root directory after it detaches. Otherwise, invoking the daemon from a carelessly chosen directory would prevent the administrator from unmounting the file system that holds that directory. Specifying --no-chdir suppresses this behavior, preventing the daemon from changing its current working directory. This may be useful for collecting core files, since it is common behavior to write core dumps into the current working directory and the root directory is not a good directory to use. This option has no effect when --detach is not specified. 📂
  • --no-self-confinement — By default this daemon will try to self-confine itself to work with files under well-known directories determined at build time. It is better to stick with this default behavior and not to use this flag unless some other Access Control is used to confine daemon. Note that in contrast to other access control implementations that are typically enforced from kernel-space (e.g. DAC or MAC), self-confinement is imposed from the user-space daemon itself and hence should not be considered as a full confinement strategy, but instead should be viewed as an additional layer of security. 🛡️
  • --user=user:group — Causes this program to run as a different user specified in user:group, thus dropping most of the root privileges. Short forms user and :group are also allowed, with current user or group assumed, respectively. Only daemons started by the root user accepts this argument. On Linux, daemons will be granted CAP_IPC_LOCK and CAP_NET_BIND_SERVICES before dropping root privileges. Daemons that interact with a datapath, such as ovs-vswitchd, will be granted three additional capabilities, namely CAP_NET_ADMIN, CAP_NET_BROADCAST and CAP_NET_RAW. The capability change will apply even if the new user is root. 👤

Logging Options 🧚

  • -v[spec], --verbose=[spec] — Sets logging levels. Without any spec, sets the log level for every module and destination to dbg. Otherwise, spec is a list of words separated by spaces or commas or colons, up to one from each category below:
    • A valid module name, as displayed by the vlog/list command on ovs-appctl(8), limits the log level change to the specified module.
    • syslog, console, or file, to limit the log level change to only to the system log, to the console, or to a file, respectively. (If --detach is specified, the daemon closes its standard file descriptors, so logging to the console will have no effect.)
    • off, emer, err, warn, info, or dbg, to control the log level. Messages of the given severity or higher will be logged, and messages of lower severity will be filtered out. off filters out all messages. See ovs-appctl(8) for a definition of each log level.

Case is not significant within spec.

Regardless of the log levels set for file, logging to a file will not take place unless --log-file is also specified (see below).

For compatibility with older versions of OVS, any is accepted as a word but has no effect.

  • -v, --verbose — Sets the maximum logging verbosity level, equivalent to --verbose=dbg. 🔥
  • -vPATTERN:destination:pattern, --verbose=PATTERN:destination:pattern — Sets the log pattern for destination to pattern. Refer to ovs-appctl(8) for a description of the valid syntax for pattern. 🎨
  • -vFACILITY:facility, --verbose=FACILITY:facility — Sets the RFC5424 facility of the log message. facility can be one of kern, user, mail, daemon, auth, syslog, lpr, news, uucp, clock, ftp, ntp, audit, alert, clock2, local0, local1, local2, local3, local4, local5, local6 or local7. If this option is not specified, daemon is used as the default for the local system syslog and local0 is used while sending a message to the target provided via the --syslog-target option. 🏷️
  • --log-file[=file] — Enables logging to a file. If file is specified, then it is used as the exact name for the log file. The default log file name used if file is omitted is /var/log/ovn/program.log. 📁
  • --syslog-target=host:port — Send syslog messages to UDP port on host, in addition to the system syslog. The host must be a numerical IP address, not a hostname. 📡
  • --syslog-method=method — Specify method as how syslog messages should be sent to syslog daemon. The following forms are supported:
    • libc, to use the libc syslog() function. Downside of using this options is that libc adds fixed prefix to every message before it is actually sent to the syslog daemon over /dev/log UNIX domain socket.
    • unix:file, to use a UNIX domain socket directly. It is possible to specify arbitrary message format with this option. However, rsyslogd 8.9 and older versions use hard coded parser function anyway that limits UNIX domain socket use. If you want to use arbitrary message format with older rsyslogd versions, then use UDP socket to localhost IP address instead.
    • udp:ip:port, to use a UDP socket. With this method it is possible to use arbitrary message format also with older rsyslogd. When sending syslog messages over UDP socket extra precaution needs to be taken into account, for example, syslog daemon needs to be configured to listen on the specified UDP port, accidental iptables rules could be interfering with local syslog traffic and there are some security considerations that apply to UDP sockets, but do not apply to UNIX domain sockets.
    • null, to discard all messages logged to syslog.

The default is taken from the OVS_SYSLOG_METHOD environment variable; if it is unset, the default is libc.

PKI Options 🔐

PKI configuration is required in order to use SSL/TLS for the connections to the Northbound and Southbound databases.

  • -p privkey.pem, --private-key=privkey.pem — Specifies a PEM file containing the private key used as identity for outgoing SSL/TLS connections. 🔑
  • -c cert.pem, --certificate=cert.pem — points at a PEM file holding a certificate that vouches for the private key you gave on -p or --private-key. That certificate must be signed by the certificate authority (CA) that the peer on your SSL/TLS connections is gonna use to verify it. no cap, it has to chain up properly or it's a no-go 💅
  • -C cacert.pem, --ca-cert=cacert.pem — points at a PEM file holding the CA certificate used to verify the certificates that SSL/TLS peers present to this program. (and yeah, this can be the same certificate that SSL/TLS peers use to verify the one you specified on -c or --certificate — or it can be a totally different one, it just depends on the PKI design you're running. iykyk.)
  • -C none, --ca-cert=none — turns OFF verification of the certificates presented by SSL/TLS peers. bestie. this is a security risk, fr fr, because it means certificates can't be verified as belonging to known trusted hosts. 🙈
  • --ssl-server-name=servername — sets the server name to use for TLS Server Name Indication (SNI). By default, the hostname from the connection string is what gets used for SNI. This option lets you override the SNI hostname, which is lowkey useful when you're connecting through proxies or service meshes where the connection endpoint is not the same as the server name you actually mean. ✨

✨ Other Options ✨

  • --unixctl=socket — sets the name of the control socket that the program listens on for runtime management commands (peep RUNTIME MANAGEMENT COMMANDS below, it's right there 👇). If socket does not begin with /, it is interpreted as relative to .. If --unixctl is not used at all, the default socket is /program.pid.ctl, where pid is the program's process ID.

Specifying none for socket disables the control socket feature entirely. poof, gone. 🫥

  • -h, --help — prints a brief help message to the console. quick lil snack of info. 🍓
  • -V, --version — prints version information to the console. 💜

💖 RUNTIME MANAGEMENT COMMANDS 💖

ovn-appctl can send commands to a running ovn-northd process. The currently supported commands are described below, and yes, they're all kinda iconic in their own way:

  • exit — causes ovn-northd to gracefully terminate. bye bestie, thanks for everything 🥹
  • pause — pauses ovn-northd. When it's paused, ovn-northd still receives changes from the Northbound and Southbound database changes as usual, but it does not send any updates. A paused ovn-northd also drops database locks, which allows any other non-paused instance of ovn-northd to take over. main character stepping aside so the understudy can shine 👑
  • resume — resumes the ovn-northd operation to process Northbound and Southbound database contents and generate logical flows. This will also instruct ovn-northd to aspire for the lock on SB DB. welcome back queen 🌸
  • is-paused — returns "true" if ovn-northd is currently paused, "false" otherwise. vibe check, paused edition.
  • status — prints this server's status. Status will be "active" if ovn-northd has acquired the OVSDB lock on SB DB, "standby" if it has not, or "paused" if this instance is paused.
  • sb-cluster-state-reset — reset southbound database cluster status when databases are destroyed and rebuilt.

If all databases in a clustered southbound database are removed from disk, then the stored index of all databases will be reset to zero. This will cause ovn-northd to be unable to read or write to the southbound database, because it will always detect the data as stale. In such a case, run this command so that ovn-northd will reset its local index so that it can interact with the southbound database again. it's giving "factory reset but just for the index" 😭

  • nb-cluster-state-reset — reset northbound database cluster status when databases are destroyed and rebuilt.

This performs the same task as sb-cluster-state-reset except for the northbound database client. same energy, different DB 💅

  • parallel-build/set-n-threads N — set the number of threads used for building logical flows. When N is within [2-256], parallelization is enabled. When N is 1, parallelization is disabled. When N is less than 1 or more than 256, an error is returned. If ovn-northd fails to start parallelization (e.g. fails to setup semaphores), parallelization is disabled and an error is returned. so basically: stay in your lane, [2-256] 🚦
  • parallel-build/get-n-threads — return the number of threads used for building logical flows. spill the number 🔢
  • nb-connection-status — prints whether the connection to the OVN Northbound database is currently connected or not.
  • sb-connection-status — prints whether the connection to the OVN Southbound database is currently connected or not.
  • debug/chassis-features-list — lists the chassis feature flags and their current values as determined by ovn-northd. These features reflect the capabilities reported by the connected chassis. it's like a little report card for every chassis 📋
  • inc-engine/show-stats — display ovn-northd engine counters. For each engine node the following counters have been added:
    • recompute
    • compute
    • abort
  • inc-engine/show-stats engine_node_name [counter_name] — display the ovn-northd engine counter(s) for the specified engine_node_name. counter_name is optional and can be one of recompute, compute or abort.
  • inc-engine/clear-stats — reset ovn-northd engine counters. clean slate era ✨
  • inc-engine/recompute — triggers a full recompute of the incremental processing engine on the next iteration. do-over, but make it on purpose 🎀
  • inc-engine/compute-log-timeout msecs — sets the timeout in milliseconds for logging engine compute events.
  • inc-engine/list-stopwatches [node] — lists the engine nodes and their change handler names. If node is specified, only the handlers for that engine node are listed.
  • inc-engine/enable-stopwatch [node] — enables the per-node and per-handler stopwatches in the incremental processing engine. If node is specified, only that node's stopwatches are enabled; otherwise all nodes are affected. While enabled, every engine node recompute and change handler invocation is timed and the results can be viewed with the stopwatch/show command. Stopwatches are disabled by default because they add measurable CPU overhead. so like, turn them on when you're investigating, not just for the aesthetic 🕰️
  • inc-engine/disable-stopwatch [node] — disables the per-node and per-handler stopwatches in the incremental processing engine. If node is specified, only that node's stopwatches are disabled; otherwise all nodes are affected. This is the default state.

👑 ACTIVE-STANDBY FOR HIGH AVAILABILITY 👑

You may run ovn-northd more than once in an OVN deployment. When connected to a standalone or clustered DB setup, OVN will automatically ensure that only one of them is active at a time. If multiple instances of ovn-northd are running and the active ovn-northd fails, one of the hot standby instances of ovn-northd will automatically take over. no awkward gap, no "who's driving", it just happens 🦋

Active-Standby with multiple OVN DB servers

You may run multiple OVN DB servers in an OVN deployment with:

  • OVN DB servers deployed in active/passive mode with one active and multiple passive ovsdb-servers.
  • ovn-northd also deployed on all these nodes, using unix ctl sockets to connect to the local OVN DB servers.

In such deployments, the ovn-northds on the passive nodes will process the DB changes and compute logical flows to be thrown out later, because write transactions are not allowed by the passive ovsdb-servers. It results in unnecessary CPU usage. 😩 doing all that work for nothing, tragic honestly.

With the help of runtime management command pause, you can pause ovn-northd on these nodes. When a passive node becomes master, you can use the runtime management command resume to resume the ovn-northd to process the DB changes. so: pause on the bench, resume when you get subbed in 🏆

🌈 LOGICAL FLOW TABLE STRUCTURE 🌈

For a detailed description of the logical flow tables that ovn-northd populates in the OVN_Southbound database — including logical switch and router datapath pipelines and drop sampling behavior — see ovn-logical-flows(7). go read it, it's the lore 📚

and that's a wrap on this page bestie 💖 it's from OVN 26.09.1, it's the ovn-northd page, section ovn-northd(8) — go forth and route, you've got this 🌟👑🦋

📦 where this page comes from