Provided by: openvswitch-switch_3.2.2-0ubuntu0.23.10.1_amd64 
NAME
ovs-ctl - OVS startup helper script
SYNOPSIS
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
DESCRIPTION
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, 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.
• --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.
OPTIONS
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.
EXIT STATUS
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.
ENVIRONMENT
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.
FILES
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.
EXAMPLE
The file debian/openvswitch-switch.init in the Open vSwitch source distribution is a good
example of how to use ovs-ctl.
SEE ALSO
README.rst, ovsdb-server(8), ovs-vswitchd(8).
AUTHOR
The Open vSwitch Development Community
COPYRIGHT
2016-2024, The Open vSwitch Development Community