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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXIT STATUS | ENVIRONMENT | FILES | EXAMPLE | SEE ALSO | AUTHOR | COPYRIGHT | COLOPHON |
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OVS-CTL(8) Open vSwitch OVS-CTL(8)
ovs-ctl - OVS startup helper script
ovs-ctl --system-id=random|<uuid> [<options>] start
ovs-ctl stop
ovs-ctl --system-id=random|<uuid> [<options>] restart
ovs-ctl status
ovs-ctl version
ovs-ctl [<options>] load-kmod
ovs-ctl --system-id=random|<uuid> [<options>] force-reload-kmod
ovs-ctl [--protocol=<protocol>] [--sport=<sport>]
[--dport=<dport>] enable-protocol
ovs-ctl delete-transient-ports
ovs-ctl help | -h | --help
ovs-ctl --version
The ovs-ctl program starts, stops, and checks the status of Open
vSwitch daemons. It is not meant to be invoked directly by system
administrators but to be called internally by system startup
scripts.
Each ovs-ctl command is described separately below.
The start command
The start command starts Open vSwitch. It performs the following
tasks:
1. Loads the Open vSwitch kernel module. If this fails, and the
Linux bridge module is loaded but no bridges exist, it tries to
unload the bridge module and tries loading the Open vSwitch
kernel module again. (This is because the Open vSwitch kernel
module cannot coexist with the Linux bridge module before
2.6.37.)
The start command skips the following steps if ovsdb-server is
already running:
2. If the Open vSwitch database file does not exist, it creates
it. If the database does exist, but it has an obsolete
version, it upgrades it to the latest schema.
3. Starts ovsdb-server, unless the --no-ovsdb-server command
option is given.
4. Initializes a few values inside the database.
5. If the --delete-bridges option was used, deletes all of the
bridges from the database.
6. If the --delete-transient-ports option was used, deletes all
ports that have other_config:transient set to true.
The start command skips the following step if ovs-vswitchd is
already running, or if the --no-ovs-vswitchd command option is
given:
7. Starts ovs-vswitchd.
Options
Several command-line options influence the start command’s
behavior. Some form of the following option should ordinarily be
specified:
• --system-id=<uuid> or --system-id=random
This specifies a unique system identifier to store into
external-ids:system-id in the database’s Open_vSwitch table.
Remote managers that talk to the Open vSwitch database server
over network protocols use this value to identify and
distinguish Open vSwitch instances, so it should be unique (at
least) within OVS instances that will connect to a single
controller.
When random is specified, ovs-ctl will generate a random ID that
persists from one run to another (stored in a file). When
another string is specified ovs-ctl uses it literally.
The following options should be specified if the defaults are not
suitable:
• --system-type=<type> or --system-version=<version>
Sets the value to store in the system-type and system-version
columns, respectively, in the database’s Open_vSwitch table.
Remote managers may use these values too determine the kind of
system to which they are connected (primarily for display to
human administrators).
When not specified, ovs-ctl uses values from the optional
system-type.conf and system-version.conf files (see Files) or it
uses the lsb_release program, if present, to provide reasonable
defaults.
The following options are also likely to be useful:
• --external-id="<name>=<value>"
Sets external-ids:<name> to <value> in the database’s
Open_vSwitch table. Specifying this option multiple times adds
multiple key-value pairs.
• --delete-bridges
Ordinarily Open vSwitch bridges persist from one system boot to
the next, as long as the database is preserved. Some
environments instead expect to re-create all of the bridges and
other configuration state on every boot. This option supports
that, by deleting all Open vSwitch bridges after starting
ovsdb-server but before starting ovs-vswitchd.
• --delete-transient-ports
Deletes all ports that have other_config:transient set to true.
This is important on certain environments where some ports are
going to be recreated after reboot, but other ports need to be
persisted in the database.
• --ovs-user=user[:group]
Ordinarily Open vSwitch daemons are started as the user invoking
the ovs-ctl command. Some system administrators would prefer to
have the various daemons spawn as different users in their
environments. This option allows passing the --user option to
the ovsdb-server and ovs-vswitchd daemons, allowing them to
change their privilege levels.
The following options are less important:
• --no-monitor
By default ovs-ctl passes --monitor to ovs-vswitchd and
ovsdb-server, requesting that it spawn a process monitor which
will restart the daemon if it crashes. This option suppresses
that behavior.
• --daemon-cwd=<directory>
Specifies the current working directory that the OVS daemons
should run from. The default is / (the root directory) if this
option is not specified. (This option is useful because most
systems create core files in a process’s current working
directory and because a file system that is in use as a
process’s current working directory cannot be unmounted.)
• --no-force-corefiles
By default, ovs-ctl enables core dumps for the OVS daemons.
This option disables that behavior.
• --no-mlockall
By default ovs-ctl passes --mlockall to ovs-vswitchd, requesting
that it lock all of its virtual memory on page fault (on
allocation, when running on Linux kernel 4.4 and older),
preventing it from being paged to disk. This option suppresses
that behavior.
• --no-self-confinement
Disable self-confinement for ovs-vswitchd and ovsdb-server
daemons. This flag may be used when, for example, OpenFlow
controller creates its Unix Domain Socket outside OVS run
directory and OVS needs to connect to it. It is better to stick
with the default behavior and not to use this flag, unless:
• You have Open vSwitch running under SELinux or AppArmor
Mandatory Access Control that would prevent OVS from messing
with sockets outside ordinary OVS directories.
• You believe that relying on protocol handshakes (e.g.
OpenFlow) is enough to prevent OVS to adversely interact with
other daemons running on your system.
• You don’t have much worries of remote OVSDB exploits in the
first place, because, perhaps, OVSDB manager is running on the
same host as OVS and share similar attack vectors.
• --oom-score=<score>
Sets the Linux Out-Of-Memory (OOM) killer score for the OVS
daemon after it’s been started.
• --ulimit-core=<LIMIT>
Sets ulimit core file size for the OVS daemon after it’s been
started.
• --ovsdb-server-priority=<niceness> or
--ovs-vswitchd-priority=<niceness>
Sets the nice(1) level used for each daemon. All of them
default to -10.
• --ovsdb-server-wrapper=<wrapper> or
--ovs-vswitchd-wrapper=<wrapper>
Configures the specified daemon to run under <wrapper>, which is
one of the following:
• valgrind: Run the daemon under valgrind(1), if it is
installed, logging to <daemon>.valgrind.log.<pid> in the log
directory.
• strace: Run the daemon under strace(1), if it is installed,
logging to <daemon>.strace.log.<pid> in the log directory.
• glibc: Enable GNU C library features designed to find memory
errors.
By default, no wrapper is used.
Each of the wrappers can expose bugs in Open vSwitch that lead
to incorrect operation, including crashes. The valgrind and
strace wrappers greatly slow daemon operations so they should
not be used in production. They also produce voluminous logs
that can quickly fill small disk partitions. The glibc wrapper
is less resource-intensive but still somewhat slows the daemons.
The following options control file locations. They should only be
used if the default locations cannot be used. See FILES, below,
for more information.
• --db-file=<file>
Overrides the file name for the OVS database.
• --db-sock=<socket>
Overrides the file name for the Unix domain socket used to
connect to ovsdb-server.
• --db-schema=<schema>
Overrides the file name for the OVS database schema.
• --extra-dbs=<file>
Adds <file> as an extra database for ovsdb-server to serve out.
Multiple space-separated file names may also be specified.
<file> should begin with /; if it does not, then it will be
taken as relative to <dbdir>.
The stop command
The stop command stops the ovs-vswitchd and ovsdb-server daemons.
It does not unload the Open vSwitch kernel modules. It can take
the same --no-ovsdb-server and --no-ovs-vswitchd options as that
of the start command.
This command does nothing and finishes successfully if the OVS
daemons aren’t running.
The restart command
The restart command performs a stop followed by a start command.
The command can take the same options as that of the start
command. In addition, it saves and restores OpenFlow flows for
each individual bridge.
The status command
The status command checks whether the OVS daemons ovs-vswitchd and
ovsdb-server are running and prints messages with that
information. It exits with status 0 if the daemons are running, 1
otherwise.
The version command
The version command runs ovsdb-server --version and ovs-vswitchd
--version.
The force-reload-kmod command
The force-reload-kmod command allows upgrading the Open vSwitch
kernel module without rebooting. It performs the following tasks:
1. Gets a list of OVS “internal” interfaces, that is, network
devices implemented by Open vSwitch. The most common examples
of these are bridge “local ports”.
2. Saves the OpenFlow flows of each bridge.
3. Stops the Open vSwitch daemons, as if by a call to ovs-ctl
stop.
4. Saves the kernel configuration state of the OVS internal
interfaces listed in step 1, including IP and IPv6 addresses
and routing table entries.
5. Unloads the Open vSwitch kernel module (including the bridge
compatibility module if it is loaded).
6. Starts OVS back up, as if by a call to ovs-ctl start. This
reloads the kernel module, restarts the OVS daemons and finally
restores the saved OpenFlow flows.
7. Restores the kernel configuration state that was saved in step
4.
8. Checks for daemons that may need to be restarted because they
have packet sockets that are listening on old instances of Open
vSwitch kernel interfaces and, if it finds any, prints a
warning on stdout. DHCP is a common example: if the ISC DHCP
client is running on an OVS internal interface, then it will
have to be restarted after completing the above procedure. (It
would be nice if ovs-ctl could restart daemons automatically,
but the details are far too specific to a particular
distribution and installation.)
force-kmod-reload internally stops and starts OVS, so it accepts
all of the options accepted by the start command except for the
--no-ovs-vswitchd option.
The load-kmod command
The load-kmod command loads the openvswitch kernel modules if they
are not already loaded. This operation also occurs as part of the
start command. The motivation for providing the load-kmod command
is to allow errors when loading modules to be handled separately
from other errors that may occur when running the start command.
By default the load-kmod command attempts to load the openvswitch
kernel module.
The enable-protocol command
The enable-protocol command checks for rules related to a
specified protocol in the system’s iptables(8) configuration. If
there are no rules specifically related to that protocol, then it
inserts a rule to accept the specified protocol.
More specifically:
• If iptables is not installed or not enabled, this command does
nothing, assuming that lack of filtering means that the protocol
is enabled.
• If the INPUT chain has a rule that matches the specified
protocol, then this command does nothing, assuming that whatever
rule is installed reflects the system administrator’s decisions.
• Otherwise, this command installs a rule that accepts traffic of
the specified protocol.
This command normally completes successfully, even if it does
nothing. Only the failure of an attempt to insert a rule normally
causes it to return an exit code other than 0.
The following options control the protocol to be enabled:
• --protocol=<protocol>
The name of the IP protocol to be enabled, such as gre or tcp.
The default is gre.
• --sport=<sport> or --dport=<dport>
TCP or UDP source or destination port to match. These are
optional and allowed only with --protocol=tcp or --protocol=udp.
The delete-transient-ports command
Deletes all ports that have the other_config:transient value set
to true.
The help command
Prints a usage message and exits successfully.
In addition to the options listed for each command above, these
options control the behavior of several ovs-ctl commands.
By default, ovs-ctl controls the ovsdb-server and ovs-vswitchd
daemons. The following options restrict that control to exclude
one or the other:
• --no-ovsdb-server
Specifies that the ovs-ctl commands start, stop, and restart
should not modify the running status of ovsdb-server.
• --no-ovs-vswitchd
Specifies that the ovs-ctl commands start, stop, and restart
should not modify the running status of ovs-vswitchd. It is an
error to include this option with the force-reload-kmod command.
ovs-ctl exits with status 0 on success and nonzero on failure.
The start command is considered to succeed if OVS is already
started; the stop command is considered to succeed if OVS is
already stopped.
The following environment variables affect ovs-ctl:
• PATH
ovs-ctl does not hardcode the location of any of the programs
that it runs. ovs-ctl will add the <sbindir> and <bindir> that
were specified at configure time to PATH, if they are not
already present.
• OVS_LOGDIR, OVS_RUNDIR, OVS_DBDIR, OVS_SYSCONFDIR,
OVS_PKGDATADIR, OVS_BINDIR, OVS_SBINDIR
Setting one of these variables in the environment overrides the
respective configure option, both for ovs-ctl itself and for the
other Open vSwitch programs that it runs.
ovs-ctl uses the following files:
• ovs-lib
Shell function library used internally by ovs-ctl. It must be
installed in the same directory as ovs-ctl.
• <logdir>/<daemon>.log
Per-daemon logfiles.
• <rundir>/<daemon>.pid
Per-daemon pidfiles to track whether a daemon is running and
with what process ID.
• <pkgdatadir>/vswitch.ovsschema
The OVS database schema used to initialize the database (use
--db-schema to override this location).
• <dbdir>/conf.db
The OVS database (use --db-file to override this location).
• <rundir>/openvswitch/db.sock
The Unix domain socket used for local communication with
ovsdb-server (use --db-sock to override this location).
• <sysconfdir>/openvswitch/system-id.conf
The persistent system UUID created and read by
--system-id=random.
• <sysconfdir>/openvswitch/system-type.conf and
<sysconfdir>/openvswitch/system-version.conf
The system-type and system-version values stored in the
database’s Open_vSwitch table when not specified as a
command-line option.
The file debian/openvswitch-switch.init in the Open vSwitch source
distribution is a good example of how to use ovs-ctl.
README.rst, ovsdb-server(8), ovs-vswitchd(8).
The Open vSwitch Development Community
2016-2024, The Open vSwitch Development Community
This page is part of the Open vSwitch (a distributed virtual
multilayer switch) project. Information about the project can be
found at ⟨http://openvswitch.org/⟩. If you have a bug report for
this manual page, send it to bugs@openvswitch.org. This page was
obtained from the project's upstream Git repository
⟨https://github.com/openvswitch/ovs.git⟩ on 2025-08-11. (At that
time, the date of the most recent commit that was found in the
repository was 2025-07-31.) If you discover any rendering
problems in this HTML version of the page, or you believe there is
a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
man-pages@man7.org
3.6.90 Aug 09, 2025 OVS-CTL(8)
Pages that refer to this page: ovs-kmod-ctl(8), ovs-vswitchd(8)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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