=======
ovs-ctl
=======

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 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.

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)``.
