yet another problem with new overlay fs

[mirror_lxc.git] / doc / lxc.container.conf.sgml.in

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<!DOCTYPE refentry PUBLIC @docdtd@ [

<!ENTITY seealso SYSTEM "@builddir@/see_also.sgml">
]>

<refentry>

  <docinfo><date>@LXC_GENERATE_DATE@</date></docinfo>

  <refmeta>
    <refentrytitle>lxc.container.conf</refentrytitle>
    <manvolnum>5</manvolnum>
  </refmeta>

  <refnamediv>
    <refname>lxc.container.conf</refname>

    <refpurpose>
      LXC container configuration file
    </refpurpose>
  </refnamediv>

  <refsect1>
    <title>Description</title>

    <para>
      The linux containers (<command>lxc</command>) are always created
      before being used. This creation defines a set of system
      resources to be virtualized / isolated when a process is using
      the container. By default, the pids, sysv ipc and mount points
      are virtualized and isolated. The other system resources are
      shared across containers, until they are explicitly defined in
      the configuration file. For example, if there is no network
      configuration, the network will be shared between the creator of
      the container and the container itself, but if the network is
      specified, a new network stack is created for the container and
      the container can no longer use the network of its ancestor.
    </para>

    <para>
      The configuration file defines the different system resources to
      be assigned for the container. At present, the utsname, the
      network, the mount points, the root file system, the user namespace,
      and the control groups are supported.
    </para>

    <para>
      Each option in the configuration file has the form <command>key
      = value</command> fitting in one line. The '#' character means
      the line is a comment.
    </para>

    <refsect2>
      <title>Configuration</title>
      <para>
        In order to ease administration of multiple related containers, it
        is possible to have a container configuration file cause another
        file to be loaded.  For instance, network configuration
        can be defined in one common file which is included by multiple
        containers.  Then, if the containers are moved to another host,
        only one file may need to be updated.
      </para>

      <variablelist>
        <varlistentry>
          <term>
            <option>lxc.include</option>
          </term>
          <listitem>
            <para>
              Specify the file to be included.  The included file must be
              in the same valid lxc configuration file format.
            </para>
          </listitem>
        </varlistentry>
      </variablelist>
    </refsect2>

    <refsect2>
      <title>Architecture</title>
      <para>
        Allows one to set the architecture for the container. For example,
        set a 32bits architecture for a container running 32bits
        binaries on a 64bits host. This fixes the container scripts
        which rely on the architecture to do some work like
        downloading the packages.
      </para>

      <variablelist>
        <varlistentry>
          <term>
            <option>lxc.arch</option>
          </term>
          <listitem>
            <para>
              Specify the architecture for the container.
            </para>
            <para>
              Valid options are
              <option>x86</option>,
              <option>i686</option>,
              <option>x86_64</option>,
              <option>amd64</option>
            </para>
          </listitem>
        </varlistentry>
      </variablelist>

    </refsect2>

    <refsect2>
      <title>Hostname</title>
      <para>
        The utsname section defines the hostname to be set for the
        container. That means the container can set its own hostname
        without changing the one from the system. That makes the
        hostname private for the container.
      </para>
      <variablelist>
        <varlistentry>
          <term>
            <option>lxc.utsname</option>
          </term>
          <listitem>
            <para>
              specify the hostname for the container
            </para>
          </listitem>
        </varlistentry>
      </variablelist>
    </refsect2>

    <refsect2>
      <title>Halt signal</title>
      <para>
    Allows one to specify signal name or number, sent by lxc-stop to the
    container's init process to cleanly shutdown the container. Different
    init systems could use different signals to perform clean shutdown
    sequence. This option allows the signal to be specified in kill(1)
    fashion, e.g. SIGPWR, SIGRTMIN+14, SIGRTMAX-10 or plain number. The
    default signal is SIGPWR.
      </para>
      <variablelist>
    <varlistentry>
      <term>
        <option>lxc.haltsignal</option>
      </term>
      <listitem>
        <para>
          specify the signal used to halt the container
        </para>
      </listitem>
    </varlistentry>
      </variablelist>
    </refsect2>

    <refsect2>
      <title>Stop signal</title>
      <para>
    Allows one to specify signal name or number, sent by lxc-stop to forcibly
    shutdown the container. This option allows signal to be specified in
    kill(1) fashion, e.g. SIGKILL, SIGRTMIN+14, SIGRTMAX-10 or plain number.
    The default signal is SIGKILL.
      </para>
      <variablelist>
    <varlistentry>
      <term>
        <option>lxc.stopsignal</option>
      </term>
      <listitem>
        <para>
          specify the signal used to stop the container
        </para>
      </listitem>
    </varlistentry>
      </variablelist>
    </refsect2>

    <refsect2>
      <title>Init command</title>
      <para>
        Sets the command to use as the init system for the containers.

        This option is ignored when using lxc-execute.

        Defaults to: /sbin/init
      </para>
      <variablelist>
    <varlistentry>
      <term>
        <option>lxc.init_cmd</option>
      </term>
      <listitem>
        <para>
          Absolute path from container rootfs to the binary to use as init.
        </para>
      </listitem>
    </varlistentry>
      </variablelist>
    </refsect2>

    <refsect2>
      <title>Network</title>
      <para>
        The network section defines how the network is virtualized in
        the container. The network virtualization acts at layer
        two. In order to use the network virtualization, parameters
        must be specified to define the network interfaces of the
        container. Several virtual interfaces can be assigned and used
        in a container even if the system has only one physical
        network interface.
      </para>
      <variablelist>
        <varlistentry>
          <term>
            <option>lxc.network.type</option>
          </term>
          <listitem>
            <para>
              specify what kind of network virtualization to be used
              for the container. Each time
              a <option>lxc.network.type</option> field is found a new
              round of network configuration begins. In this way,
              several network virtualization types can be specified
              for the same container, as well as assigning several
              network interfaces for one container. The different
              virtualization types can be:
            </para>

            <para>
              <option>none:</option> will cause the container to share
              the host's network namespace.  This means the host
              network devices are usable in the container.  It also
              means that if both the container and host have upstart as
              init, 'halt' in a container (for instance) will shut down the
              host.
            </para>

            <para>
              <option>empty:</option> will create only the loopback
              interface.
            </para>

            <para>
              <option>veth:</option> a virtual ethernet pair
              device is created with one side assigned to the container
              and the other side attached to a bridge specified by
              the <option>lxc.network.link</option> option.
              If the bridge is not specified, then the veth pair device
              will be created but not attached to any bridge.
              Otherwise, the bridge has to be created on the system
              before starting the container.
              <command>lxc</command> won't handle any
              configuration outside of the container.
              By default, <command>lxc</command> chooses a name for the
              network device belonging to the outside of the
              container, but if you wish to handle
              this name yourselves, you can tell <command>lxc</command>
              to set a specific name with
              the <option>lxc.network.veth.pair</option> option (except for
              unprivileged containers where this option is ignored for security
              reasons).
            </para>

            <para>
              <option>vlan:</option> a vlan interface is linked with
              the interface specified by
              the <option>lxc.network.link</option> and assigned to
              the container. The vlan identifier is specified with the
              option <option>lxc.network.vlan.id</option>.
            </para>

            <para>
              <option>macvlan:</option> a macvlan interface is linked
              with the interface specified by
              the <option>lxc.network.link</option> and assigned to
              the container.
              <option>lxc.network.macvlan.mode</option> specifies the
              mode the macvlan will use to communicate between
              different macvlan on the same upper device. The accepted
              modes are <option>private</option>, the device never
              communicates with any other device on the same upper_dev (default),
              <option>vepa</option>, the new Virtual Ethernet Port
              Aggregator (VEPA) mode, it assumes that the adjacent
              bridge returns all frames where both source and
              destination are local to the macvlan port, i.e. the
              bridge is set up as a reflective relay.  Broadcast
              frames coming in from the upper_dev get flooded to all
              macvlan interfaces in VEPA mode, local frames are not
              delivered locally, or <option>bridge</option>, it
              provides the behavior of a simple bridge between
              different macvlan interfaces on the same port. Frames
              from one interface to another one get delivered directly
              and are not sent out externally. Broadcast frames get
              flooded to all other bridge ports and to the external
              interface, but when they come back from a reflective
              relay, we don't deliver them again.  Since we know all
              the MAC addresses, the macvlan bridge mode does not
              require learning or STP like the bridge module does.
            </para>

            <para>
              <option>phys:</option> an already existing interface
              specified by the <option>lxc.network.link</option> is
              assigned to the container.
            </para>
          </listitem>
          </varlistentry>

        <varlistentry>
          <term>
            <option>lxc.network.flags</option>
          </term>
          <listitem>
            <para>
              specify an action to do for the
              network.
            </para>

            <para><option>up:</option> activates the interface.
            </para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>
            <option>lxc.network.link</option>
          </term>
          <listitem>
            <para>
              specify the interface to be used for real network
              traffic.
            </para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>
            <option>lxc.network.mtu</option>
          </term>
          <listitem>
            <para>
              specify the maximum transfer unit for this interface.
            </para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>
            <option>lxc.network.name</option>
          </term>
          <listitem>
            <para>
              the interface name is dynamically allocated, but if
              another name is needed because the configuration files
              being used by the container use a generic name,
              eg. eth0, this option will rename the interface in the
              container.
            </para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>
            <option>lxc.network.hwaddr</option>
          </term>
          <listitem>
            <para>
              the interface mac address is dynamically allocated by
              default to the virtual interface, but in some cases,
              this is needed to resolve a mac address conflict or to
              always have the same link-local ipv6 address.
              Any "x" in address will be replaced by random value,
              this allows setting hwaddr templates.
            </para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>
            <option>lxc.network.ipv4</option>
          </term>
          <listitem>
            <para>
              specify the ipv4 address to assign to the virtualized
              interface. Several lines specify several ipv4 addresses.
              The address is in format x.y.z.t/m,
              eg. 192.168.1.123/24. The broadcast address should be
              specified on the same line, right after the ipv4
              address.
            </para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>
            <option>lxc.network.ipv4.gateway</option>
          </term>
          <listitem>
            <para>
              specify the ipv4 address to use as the gateway inside the
              container. The address is in format x.y.z.t, eg.
              192.168.1.123.

              Can also have the special value <option>auto</option>,
              which means to take the primary address from the bridge
              interface (as specified by the
              <option>lxc.network.link</option> option) and use that as
              the gateway. <option>auto</option> is only available when
              using the <option>veth</option> and
              <option>macvlan</option> network types.
            </para>
          </listitem>
        </varlistentry>


        <varlistentry>
          <term>
            <option>lxc.network.ipv6</option>
          </term>
          <listitem>
            <para>
              specify the ipv6 address to assign to the virtualized
              interface. Several lines specify several ipv6 addresses.
              The address is in format x::y/m,
              eg. 2003:db8:1:0:214:1234:fe0b:3596/64
            </para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>
            <option>lxc.network.ipv6.gateway</option>
          </term>
          <listitem>
            <para>
              specify the ipv6 address to use as the gateway inside the
              container. The address is in format x::y,
              eg. 2003:db8:1:0::1

              Can also have the special value <option>auto</option>,
              which means to take the primary address from the bridge
              interface (as specified by the
              <option>lxc.network.link</option> option) and use that as
              the gateway. <option>auto</option> is only available when
              using the <option>veth</option> and
              <option>macvlan</option> network types.
            </para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>
            <option>lxc.network.script.up</option>
          </term>
          <listitem>
            <para>
              add a configuration option to specify a script to be
              executed after creating and configuring the network used
              from the host side. The following arguments are passed
              to the script: container name and config section name
              (net) Additional arguments depend on the config section
              employing a script hook; the following are used by the
              network system: execution context (up), network type
              (empty/veth/macvlan/phys), Depending on the network
              type, other arguments may be passed:
              veth/macvlan/phys. And finally (host-sided) device name.
            </para>
            <para>
              Standard output from the script is logged at debug level.
              Standard error is not logged, but can be captured by the
              hook redirecting its standard error to standard output.
            </para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>
            <option>lxc.network.script.down</option>
          </term>
          <listitem>
            <para>
              add a configuration option to specify a script to be
              executed before destroying the network used from the
              host side. The following arguments are passed to the
              script: container name and config section name (net)
              Additional arguments depend on the config section
              employing a script hook; the following are used by the
              network system: execution context (down), network type
              (empty/veth/macvlan/phys), Depending on the network
              type, other arguments may be passed:
              veth/macvlan/phys. And finally (host-sided) device name.
            </para>
            <para>
              Standard output from the script is logged at debug level.
              Standard error is not logged, but can be captured by the
              hook redirecting its standard error to standard output.
            </para>
          </listitem>
        </varlistentry>
      </variablelist>
    </refsect2>

    <refsect2>
      <title>New pseudo tty instance (devpts)</title>
      <para>
        For stricter isolation the container can have its own private
        instance of the pseudo tty.
      </para>
      <variablelist>
        <varlistentry>
          <term>
            <option>lxc.pts</option>
          </term>
          <listitem>
            <para>
              If set, the container will have a new pseudo tty
              instance, making this private to it. The value specifies
              the maximum number of pseudo ttys allowed for a pts
              instance (this limitation is not implemented yet).
            </para>
          </listitem>
        </varlistentry>
      </variablelist>
    </refsect2>

    <refsect2>
      <title>Container system console</title>
      <para>
        If the container is configured with a root filesystem and the
        inittab file is setup to use the console, you may want to specify
        where the output of this console goes.
      </para>
      <variablelist>
        <varlistentry>
          <term>
            <option>lxc.console.logfile</option>
          </term>
          <listitem>
            <para>
              Specify a path to a file where the console output will
              be written.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>
            <option>lxc.console</option>
          </term>
          <listitem>
            <para>
              Specify a path to a device to which the console will be
              attached.  The keyword 'none' will simply disable the
              console.  This is dangerous once if have a rootfs with a
              console device file where the application can write, the
              messages will fall in the host.
            </para>
          </listitem>
        </varlistentry>
      </variablelist>
    </refsect2>

    <refsect2>
      <title>Console through the ttys</title>
      <para>
        This option is useful if the container is configured with a root
        filesystem and the inittab file is setup to launch a getty on the
        ttys. The option specifies the number of ttys to be available for
        the container. The number of gettys in the inittab file of the
        container should not be greater than the number of ttys        specified
        in this option, otherwise the excess getty sessions will die and
        respawn indefinitely giving annoying messages on the console or in
        <filename>/var/log/messages</filename>.
      </para>
      <variablelist>
        <varlistentry>
          <term>
            <option>lxc.tty</option>
          </term>
          <listitem>
            <para>
              Specify the number of tty to make available to the
              container.
            </para>
          </listitem>
        </varlistentry>
      </variablelist>
    </refsect2>

    <refsect2>
      <title>Console devices location</title>
      <para>
        LXC consoles are provided through Unix98 PTYs created on the
        host and bind-mounted over the expected devices in the container.
        By default, they are bind-mounted over <filename>/dev/console</filename>
        and <filename>/dev/ttyN</filename>.  This can prevent package upgrades
        in the guest.  Therefore you can specify a directory location (under
        <filename>/dev</filename> under which LXC will create the files and
        bind-mount over them.  These will then be symbolically linked to
        <filename>/dev/console</filename> and <filename>/dev/ttyN</filename>.
        A package upgrade can then succeed as it is able to remove and replace
        the symbolic links.
      </para>
      <variablelist>
        <varlistentry>
          <term>
            <option>lxc.devttydir</option>
          </term>
          <listitem>
            <para>
              Specify a directory under <filename>/dev</filename>
              under which to create the container console devices.
            </para>
          </listitem>
        </varlistentry>
      </variablelist>
    </refsect2>

    <refsect2>
      <title>/dev directory</title>
      <para>
        By default, lxc creates a few symbolic links (fd,stdin,stdout,stderr)
        in the container's <filename>/dev</filename> directory but does not
        automatically create device node entries. This allows the container's
        <filename>/dev</filename> to be set up as needed in the container
        rootfs.  If lxc.autodev is set to 1, then after mounting the container's
        rootfs LXC will mount a fresh tmpfs under <filename>/dev</filename>
        (limited to 100k) and fill in a minimal set of initial devices.
        This is generally required when starting a container containing
        a "systemd" based "init" but may be optional at other times.  Additional
        devices in the containers /dev directory may be created through the
        use of the <option>lxc.hook.autodev</option> hook.
      </para>
      <variablelist>
        <varlistentry>
          <term>
            <option>lxc.autodev</option>
          </term>
          <listitem>
            <para>
              Set this to 1 to have LXC mount and populate a minimal
              <filename>/dev</filename> when starting the container.
            </para>
          </listitem>
        </varlistentry>
      </variablelist>
    </refsect2>

    <refsect2>
      <title>Enable kmsg symlink</title>
      <para>
      Enable creating /dev/kmsg as symlink to /dev/console.  This defaults to 1.
      </para>
      <variablelist>
    <varlistentry>
      <term>
        <option>lxc.kmsg</option>
      </term>
      <listitem>
        <para>
          Set this to 0 to disable /dev/kmsg symlinking.
        </para>
      </listitem>
    </varlistentry>
      </variablelist>
    </refsect2>

    <refsect2>
      <title>Mount points</title>
      <para>
        The mount points section specifies the different places to be
        mounted. These mount points will be private to the container
        and won't be visible by the processes running outside of the
        container. This is useful to mount /etc, /var or /home for
        examples.
      </para>
      <variablelist>
        <varlistentry>
          <term>
            <option>lxc.mount</option>
          </term>
          <listitem>
            <para>
              specify a file location in
              the <filename>fstab</filename> format, containing the
              mount information.  The mount target location can and in
              most cases should be a relative path, which will become
              relative to the mounted container root.  For instance,
             </para>
<screen>
proc proc proc nodev,noexec,nosuid 0 0
</screen>
             <para>
              Will mount a proc filesystem under the container's /proc,
              regardless of where the root filesystem comes from.  This
              is resilient to block device backed filesystems as well as
              container cloning.
             </para>
             <para>
              Note that when mounting a filesystem from an
              image file or block device the third field (fs_vfstype)
              cannot be auto as with
              <citerefentry>
                <refentrytitle>mount</refentrytitle>
                <manvolnum>8</manvolnum>
              </citerefentry>
              but must be explicitly specified.
            </para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>
            <option>lxc.mount.entry</option>
          </term>
          <listitem>
            <para>
              specify a mount point corresponding to a line in the
              fstab format.
            </para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>
            <option>lxc.mount.auto</option>
          </term>
          <listitem>
            <para>
              specify which standard kernel file systems should be
              automatically mounted. This may dramatically simplify
              the configuration. The file systems are:
            </para>
            <itemizedlist>
              <listitem>
                <para>
                  <option>proc:mixed</option> (or <option>proc</option>):
                  mount <filename>/proc</filename> as read-write, but
                  remount <filename>/proc/sys</filename> and
                  <filename>/proc/sysrq-trigger</filename> read-only
                  for security / container isolation purposes.
                </para>
              </listitem>
              <listitem>
                <para>
                  <option>proc:rw</option>: mount
                  <filename>/proc</filename> as read-write
                </para>
              </listitem>
              <listitem>
                <para>
                  <option>sys:ro</option> (or <option>sys</option>):
                  mount <filename>/sys</filename> as read-only
                  for security / container isolation purposes.
                </para>
              </listitem>
              <listitem>
                <para>
                  <option>sys:rw</option>: mount
                  <filename>/sys</filename> as read-write
                </para>
              </listitem>
              <listitem>
                <para>
                  <option>cgroup:mixed</option>:
                  mount a tmpfs to <filename>/sys/fs/cgroup</filename>,
                  create directories for all hierarchies to which
                  the container is added, create subdirectories
                  there with the name of the cgroup, and bind-mount
                  the container's own cgroup into that directory.
                  The container will be able to write to its own
                  cgroup directory, but not the parents, since they
                  will be remounted read-only
                </para>
              </listitem>
              <listitem>
                <para>
                  <option>cgroup:ro</option>: similar to
                  <option>cgroup:mixed</option>, but everything will
                be mounted read-only.
                </para>
              </listitem>
              <listitem>
                <para>
                  <option>cgroup:rw</option>: similar to
                  <option>cgroup:mixed</option>, but everything will
                  be mounted read-write. Note that the paths leading
                  up to the container's own cgroup will be writable,
                  but will not be a cgroup filesystem but just part
                  of the tmpfs of <filename>/sys/fs/cgroup</filename>
                </para>
              </listitem>
              <listitem>
                <para>
                  <option>cgroup</option> (without specifier):
                  defaults to <option>cgroup:rw</option> if the
                  container retains the CAP_SYS_ADMIN capability,
                  <option>cgroup:mixed</option> otherwise.
                </para>
              </listitem>
              <listitem>
                <para>
                  <option>cgroup-full:mixed</option>:
                  mount a tmpfs to <filename>/sys/fs/cgroup</filename>,
                  create directories for all hierarchies to which
                  the container is added, bind-mount the hierarchies
                  from the host to the container and make everything
                  read-only except the container's own cgroup. Note
                  that compared to <option>cgroup</option>, where
                  all paths leading up to the container's own cgroup
                  are just simple directories in the underlying
                  tmpfs, here
                  <filename>/sys/fs/cgroup/$hierarchy</filename>
                  will contain the host's full cgroup hierarchy,
                  albeit read-only outside the container's own cgroup.
                  This may leak quite a bit of information into the
                  container.
                </para>
              </listitem>
              <listitem>
                <para>
                  <option>cgroup-full:ro</option>: similar to
                  <option>cgroup-full:mixed</option>, but everything
                  will be mounted read-only.
                </para>
              </listitem>
              <listitem>
                <para>
                  <option>cgroup-full:rw</option>: similar to
                  <option>cgroup-full:mixed</option>, but everything
                  will be mounted read-write. Note that in this case,
                  the container may escape its own cgroup. (Note also
                  that if the container has CAP_SYS_ADMIN support
                  and can mount the cgroup filesystem itself, it may
                  do so anyway.)
                </para>
              </listitem>
              <listitem>
                <para>
                  <option>cgroup-full</option> (without specifier):
                  defaults to <option>cgroup-full:rw</option> if the
                  container retains the CAP_SYS_ADMIN capability,
                  <option>cgroup-full:mixed</option> otherwise.
                </para>
              </listitem>
            </itemizedlist>
            <para>
              Note that if automatic mounting of the cgroup filesystem
              is enabled, the tmpfs under
              <filename>/sys/fs/cgroup</filename> will always be
              mounted read-write (but for the <option>:mixed</option>
              and <option>:ro</option> cases, the individual
              hierarchies,
              <filename>/sys/fs/cgroup/$hierarchy</filename>, will be
              read-only). This is in order to work around a quirk in
              Ubuntu's
              <citerefentry>
                <refentrytitle>mountall</refentrytitle>
                <manvolnum>8</manvolnum>
              </citerefentry>
              command that will cause containers to wait for user
              input at boot if
              <filename>/sys/fs/cgroup</filename> is mounted read-only
              and the container can't remount it read-write due to a
              lack of CAP_SYS_ADMIN.
            </para>
            <para>
              Examples:
            </para>
            <programlisting>
              lxc.mount.auto = proc sys cgroup
              lxc.mount.auto = proc:rw sys:rw cgroup-full:rw
            </programlisting>
          </listitem>
        </varlistentry>

      </variablelist>
    </refsect2>

    <refsect2>
      <title>Root file system</title>
      <para>
        The root file system of the container can be different than that
        of the host system.
      </para>
      <variablelist>
        <varlistentry>
          <term>
            <option>lxc.rootfs</option>
          </term>
          <listitem>
            <para>
              specify the root file system for the container. It can
              be an image file, a directory or a block device. If not
              specified, the container shares its root file system
              with the host.
            </para>
            <para>
          For directory or simple block-device backed containers,
          a pathname can be used.  If the rootfs is backed by a nbd
          device, then <filename>nbd:file:1</filename> specifies that
          <filename>file</filename> should be attached to a nbd device,
          and partition 1 should be mounted as the rootfs.
          <filename>nbd:file</filename> specifies that the nbd device
          itself should be mounted.  <filename>overlayfs:/lower:/upper</filename>
          specifies that the rootfs should be an overlay with <filename>/upper</filename>
          being mounted read-write over a read-only mount of <filename>/lower</filename>.
          <filename>aufs:/lower:/upper</filename> does the same using aufs in place
          of overlayfs. <filename>loop:/file</filename> tells lxc to attach
          <filename>/file</filename> to a loop device and mount the loop device.
            </para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>
            <option>lxc.rootfs.mount</option>
          </term>
          <listitem>
            <para>
              where to recursively bind <option>lxc.rootfs</option>
              before pivoting.  This is to ensure success of the
              <citerefentry>
                <refentrytitle><command>pivot_root</command></refentrytitle>
                <manvolnum>8</manvolnum>
              </citerefentry>
              syscall.  Any directory suffices, the default should
              generally work.
            </para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>
            <option>lxc.rootfs.options</option>
          </term>
          <listitem>
            <para>
              extra mount options to use when mounting the rootfs.
            </para>
          </listitem>
        </varlistentry>

      </variablelist>
    </refsect2>

    <refsect2>
      <title>Control group</title>
      <para>
        The control group section contains the configuration for the
        different subsystem. <command>lxc</command> does not check the
        correctness of the subsystem name. This has the disadvantage
        of not detecting configuration errors until the container is
        started, but has the advantage of permitting any future
        subsystem.
      </para>
      <variablelist>
        <varlistentry>
          <term>
            <option>lxc.cgroup.[subsystem name]</option>
          </term>
          <listitem>
            <para>
              specify the control group value to be set.  The
              subsystem name is the literal name of the control group
              subsystem.  The permitted names and the syntax of their
              values is not dictated by LXC, instead it depends on the
              features of the Linux kernel running at the time the
              container is started,
              eg. <option>lxc.cgroup.cpuset.cpus</option>
            </para>
          </listitem>
        </varlistentry>
      </variablelist>
    </refsect2>

    <refsect2>
      <title>Capabilities</title>
      <para>
        The capabilities can be dropped in the container if this one
        is run as root.
      </para>
      <variablelist>
        <varlistentry>
          <term>
            <option>lxc.cap.drop</option>
          </term>
          <listitem>
            <para>
              Specify the capability to be dropped in the container. A
              single line defining several capabilities with a space
              separation is allowed. The format is the lower case of
              the capability definition without the "CAP_" prefix,
              eg. CAP_SYS_MODULE should be specified as
              sys_module. See
              <citerefentry>
                <refentrytitle><command>capabilities</command></refentrytitle>
                <manvolnum>7</manvolnum>
              </citerefentry>,
            </para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>
            <option>lxc.cap.keep</option>
          </term>
          <listitem>
            <para>
              Specify the capability to be kept in the container. All other
              capabilities will be dropped. When a special value of "none" is
              encountered, lxc will clear any keep capabilities specified up
              to this point. A value of "none" alone can be used to drop all
              capabilities.
            </para>
          </listitem>
        </varlistentry>
      </variablelist>
    </refsect2>

    <refsect2>
      <title>Apparmor profile</title>
      <para>
        If lxc was compiled and installed with apparmor support, and the host
        system has apparmor enabled, then the apparmor profile under which the
        container should be run can be specified in the container
        configuration.  The default is <command>lxc-container-default</command>.
      </para>
      <variablelist>
        <varlistentry>
          <term>
            <option>lxc.aa_profile</option>
          </term>
          <listitem>
            <para>
              Specify the apparmor profile under which the container should
              be run.  To specify that the container should be unconfined,
              use
            </para>
              <programlisting>lxc.aa_profile = unconfined</programlisting>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>
            <option>lxc.aa_allow_incomplete</option>
          </term>
          <listitem>
            <para>
              Apparmor profiles are pathname based.  Therefore many file
              restrictions require mount restrictions to be effective against
              a determined attacker.  However, these mount restrictions are not
              yet implemented in the upstream kernel.  Without the mount
              restrictions, the apparmor profiles still protect against accidental
              damager.
            </para>
            <para>
              If this flag is 0 (default), then the container will not be
              started if the kernel lacks the apparmor mount features, so that a
              regression after a kernel upgrade will be detected.  To start the
              container under partial apparmor protection, set this flag to 1.
            </para>
          </listitem>
        </varlistentry>
      </variablelist>
    </refsect2>

    <refsect2>
      <title>SELinux context</title>
      <para>
        If lxc was compiled and installed with SELinux support, and the host
        system has SELinux enabled, then the SELinux context under which the
        container should be run can be specified in the container
        configuration.  The default is <command>unconfined_t</command>,
        which means that lxc will not attempt to change contexts.
        See @DATADIR@/lxc/selinux/lxc.te for an example policy and more
        information.
      </para>
      <variablelist>
        <varlistentry>
          <term>
            <option>lxc.se_context</option>
          </term>
          <listitem>
            <para>
              Specify the SELinux context under which the container should
              be run or <command>unconfined_t</command>. For example
            </para>
            <programlisting>lxc.se_context = system_u:system_r:lxc_t:s0:c22</programlisting>
          </listitem>
        </varlistentry>
      </variablelist>
    </refsect2>

    <refsect2>
      <title>Seccomp configuration</title>
      <para>
        A container can be started with a reduced set of available
        system calls by loading a seccomp profile at startup.  The
        seccomp configuration file must begin with a version number
        on the first line, a policy type on the second line, followed
        by the configuration.
      </para>
      <para>
        Versions 1 and 2 are currently supported.  In version 1, the
        policy is a simple whitelist.  The second line therefore must
        read "whitelist", with the rest of the file containing one (numeric)
        sycall number per line.  Each syscall number is whitelisted,
        while every unlisted number is blacklisted for use in the container
      </para>

      <para>
       In version 2, the policy may be blacklist or whitelist,
       supports per-rule and per-policy default actions, and supports
       per-architecture system call resolution from textual names.
      </para>
      <para>
       An example blacklist policy, in which all system calls are
       allowed except for mknod, which will simply do nothing and
       return 0 (success), looks like:
      </para>
<screen>
2
blacklist
mknod errno 0
</screen>
      <variablelist>
        <varlistentry>
          <term>
            <option>lxc.seccomp</option>
          </term>
          <listitem>
            <para>
              Specify a file containing the seccomp configuration to
              load before the container starts.
             </para>
          </listitem>
        </varlistentry>
      </variablelist>
    </refsect2>

    <refsect2>
      <title>UID mappings</title>
      <para>
        A container can be started in a private user namespace with
        user and group id mappings.  For instance, you can map userid
        0 in the container to userid 200000 on the host.  The root
        user in the container will be privileged in the container,
        but unprivileged on the host.  Normally a system container
        will want a range of ids, so you would map, for instance,
        user and group ids 0 through 20,000 in the container to the
        ids 200,000 through 220,000.
      </para>
      <variablelist>
        <varlistentry>
          <term>
            <option>lxc.id_map</option>
          </term>
          <listitem>
            <para>
              Four values must be provided.  First a character, either
              'u', or 'g', to specify whether user or group ids are
              being mapped.  Next is the first userid as seen in the
              user namespace of the container.  Next is the userid as
              seen on the host.  Finally, a range indicating the number
              of consecutive ids to map.
             </para>
          </listitem>
        </varlistentry>
      </variablelist>
    </refsect2>

    <refsect2>
      <title>Container hooks</title>
      <para>
        Container hooks are programs or scripts which can be executed
        at various times in a container's lifetime.
      </para>
      <para>
        When a container hook is executed, information is passed both
        as command line arguments and through environment variables.
        The arguments are:
        <itemizedlist>
          <listitem><para> Container name. </para></listitem>
          <listitem><para> Section (always 'lxc'). </para></listitem>
          <listitem><para> The hook type (i.e. 'clone' or 'pre-mount'). </para></listitem>
          <listitem><para> Additional arguments In the
          case of the clone hook, any extra arguments passed to
          lxc-clone will appear as further arguments to the hook. </para></listitem>
        </itemizedlist>
        The following environment variables are set:
        <itemizedlist>
          <listitem><para> LXC_NAME: is the container's name. </para></listitem>
          <listitem><para> LXC_ROOTFS_MOUNT: the path to the mounted root filesystem. </para></listitem>
          <listitem><para> LXC_CONFIG_FILE: the path to the container configuration file. </para></listitem>
          <listitem><para> LXC_SRC_NAME: in the case of the clone hook, this is the original container's name. </para></listitem>
          <listitem><para> LXC_ROOTFS_PATH: this is the lxc.rootfs entry for the container.  Note this is likely not where the mounted rootfs is to be found, use LXC_ROOTFS_MOUNT for that. </para></listitem>
        </itemizedlist>
      </para>
      <para>
        Standard output from the hooks is logged at debug level.
        Standard error is not logged, but can be captured by the
        hook redirecting its standard error to standard output.
      </para>
      <variablelist>
        <varlistentry>
          <term>
            <option>lxc.hook.pre-start</option>
          </term>
          <listitem>
            <para>
              A hook to be run in the host's namespace before the
              container ttys, consoles, or mounts are up.
            </para>
          </listitem>
        </varlistentry>
      </variablelist>
      <variablelist>
        <varlistentry>
          <term>
            <option>lxc.hook.pre-mount</option>
          </term>
          <listitem>
            <para>
              A hook to be run in the container's fs namespace but before
              the rootfs has been set up.  This allows for manipulation
              of the rootfs, i.e. to mount an encrypted filesystem.  Mounts
              done in this hook will not be reflected on the host (apart from
              mounts propagation), so they will be automatically cleaned up
              when the container shuts down.
            </para>
          </listitem>
        </varlistentry>
      </variablelist>
      <variablelist>
        <varlistentry>
          <term>
            <option>lxc.hook.mount</option>
          </term>
          <listitem>
            <para>
              A hook to be run in the container's namespace after
              mounting has been done, but before the pivot_root.
            </para>
          </listitem>
        </varlistentry>
      </variablelist>
      <variablelist>
        <varlistentry>
          <term>
            <option>lxc.hook.autodev</option>
          </term>
          <listitem>
            <para>
              A hook to be run in the container's namespace after
              mounting has been done and after any mount hooks have
              run, but before the pivot_root, if
              <option>lxc.autodev</option> == 1.
              The purpose of this hook is to assist in populating the
              /dev directory of the container when using the autodev
              option for systemd based containers.  The container's /dev
              directory is relative to the
              ${<option>LXC_ROOTFS_MOUNT</option>} environment
              variable available when the hook is run.
            </para>
          </listitem>
        </varlistentry>
      </variablelist>
      <variablelist>
        <varlistentry>
          <term>
            <option>lxc.hook.start</option>
          </term>
          <listitem>
            <para>
              A hook to be run in the container's namespace immediately
              before executing the container's init.  This requires the
              program to be available in the container.
            </para>
          </listitem>
        </varlistentry>
      </variablelist>
      <variablelist>
        <varlistentry>
          <term>
            <option>lxc.hook.post-stop</option>
          </term>
          <listitem>
            <para>
              A hook to be run in the host's namespace after the
              container has been shut down.
            </para>
          </listitem>
        </varlistentry>
      </variablelist>
      <variablelist>
        <varlistentry>
          <term>
            <option>lxc.hook.clone</option>
          </term>
          <listitem>
            <para>
              A hook to be run when the container is cloned to a new one.
              See <citerefentry><refentrytitle><command>lxc-clone</command></refentrytitle>
              <manvolnum>1</manvolnum></citerefentry> for more information.
            </para>
          </listitem>
        </varlistentry>
      </variablelist>
    </refsect2>

    <refsect2>
      <title>Container hooks Environment Variables</title>
      <para>
        A number of environment variables are made available to the startup
        hooks to provide configuration information and assist in the
        functioning of the hooks.  Not all variables are valid in all
        contexts.  In particular, all paths are relative to the host system
        and, as such, not valid during the <option>lxc.hook.start</option> hook.
      </para>
      <variablelist>
        <varlistentry>
          <term>
            <option>LXC_NAME</option>
          </term>
          <listitem>
            <para>
              The LXC name of the container.  Useful for logging messages
              in common log environments.  [<option>-n</option>]
            </para>
          </listitem>
        </varlistentry>
      </variablelist>
      <variablelist>
        <varlistentry>
          <term>
            <option>LXC_CONFIG_FILE</option>
          </term>
          <listitem>
            <para>
              Host relative path to the container configuration file.  This
              gives the container to reference the original, top level,
              configuration file for the container in order to locate any
              additional configuration information not otherwise made
              available.  [<option>-f</option>]
            </para>
          </listitem>
        </varlistentry>
      </variablelist>
      <variablelist>
        <varlistentry>
          <term>
            <option>LXC_CONSOLE</option>
          </term>
          <listitem>
            <para>
              The path to the console output of the container if not NULL.
              [<option>-c</option>] [<option>lxc.console</option>]
            </para>
          </listitem>
        </varlistentry>
      </variablelist>
      <variablelist>
        <varlistentry>
          <term>
            <option>LXC_CONSOLE_LOGPATH</option>
          </term>
          <listitem>
            <para>
              The path to the console log output of the container if not NULL.
              [<option>-L</option>]
            </para>
          </listitem>
        </varlistentry>
      </variablelist>
      <variablelist>
        <varlistentry>
          <term>
            <option>LXC_ROOTFS_MOUNT</option>
          </term>
          <listitem>
            <para>
              The mount location to which the container is initially bound.
              This will be the host relative path to the container rootfs
              for the container instance being started and is where changes
              should be made for that instance.
              [<option>lxc.rootfs.mount</option>]
            </para>
          </listitem>
        </varlistentry>
      </variablelist>
      <variablelist>
        <varlistentry>
          <term>
            <option>LXC_ROOTFS_PATH</option>
          </term>
          <listitem>
            <para>
              The host relative path to the container root which has been
              mounted to the rootfs.mount location.
              [<option>lxc.rootfs</option>]
            </para>
          </listitem>
        </varlistentry>
      </variablelist>

    </refsect2>
    <refsect2>
    <title>Logging</title>
    <para>
      Logging can be configured on a per-container basis.  By default,
      depending upon how the lxc package was compiled, container startup
      is logged only at the ERROR level, and logged to a file named after
      the container (with '.log' appended) either under the container path,
      or under @LOGPATH@.
    </para>
    <para>
      Both the default log level and the log file can be specified in the
      container configuration file, overriding the default behavior.  Note
      that the configuration file entries can in turn be overridden by the
      command line options to <command>lxc-start</command>.
    </para>
      <variablelist>
        <varlistentry>
          <term>
            <option>lxc.loglevel</option>
          </term>
          <listitem>
            <para>
            The level at which to log.  The log level is an integer in
            the range of 0..8 inclusive, where a lower number means more
            verbose debugging.  In particular 0 = trace, 1 = debug, 2 =
            info, 3 = notice, 4 = warn, 5 = error, 6 = critical, 7 =
            alert, and 8 = fatal.  If unspecified, the level defaults
            to 5 (error), so that only errors and above are logged.
            </para>
            <para>
            Note that when a script (such as either a hook script or a
            network interface up or down script) is called, the script's
            standard output is logged at level 1, debug.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>
            <option>lxc.logfile</option>
          </term>
          <listitem>
            <para>
            The file to which logging info should be written.
            </para>
          </listitem>
        </varlistentry>
      </variablelist>
    </refsect2>

    <refsect2>
    <title>Autostart</title>
    <para>
        The autostart options support marking which containers should be
        auto-started and in what order. These options may be used by LXC tools
        directly or by external tooling provided by the distributions.
    </para>

    <variablelist>
        <varlistentry>
          <term>
            <option>lxc.start.auto</option>
          </term>
          <listitem>
            <para>
              Whether the container should be auto-started.
              Valid values are 0 (off) and 1 (on).
            </para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>
            <option>lxc.start.delay</option>
          </term>
          <listitem>
            <para>
              How long to wait (in seconds) after the container is
              started before starting the next one.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>
            <option>lxc.start.order</option>
          </term>
          <listitem>
            <para>
              An integer used to sort the containers when auto-starting
              a series of containers at once.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>
            <option>lxc.group</option>
          </term>
          <listitem>
            <para>
              A multi-value key (can be used multiple times) to put the
              container in a container group. Those groups can then be
              used (amongst other things) to start a series of related
              containers.
            </para>
          </listitem>
        </varlistentry>
      </variablelist>
    </refsect2>

    <refsect2>
    <title>Autostart and System Boot</title>
    <para>
          Each container can be part of any number of groups or no group at all.
          Two groups are special. One is the NULL group, i.e. the container does
          not belong to any group. The other group is the "onboot" group.
    </para>

    <para>
          When the system boots with the LXC service enabled, it will first
          attempt to boot any containers with lxc.start.auto == 1 that is a member
          of the "onboot" group. The startup will be in order of lxc.start.order.
          If an lxc.start.delay has been specified, that delay will be honored
          before attempting to start the next container to give the current
          container time to begin initialization and reduce overloading the host
          system. After starting the members of the "onboot" group, the LXC system
          will proceed to boot containers with lxc.start.auto == 1 which are not
          members of any group (the NULL group) and proceed as with the onboot
          group.
    </para>

    </refsect2>

    <refsect2>
      <title>Container Environment</title>
      <para>
        If you want to pass environment variables into the container (that
        is, environment variables which will be available to init and all of
        its descendents), you can use <command>lxc.environment</command>
        parameters to do so.  Be careful that you do not pass in anything
        sensitive; any process in the container which doesn't have its
        environment scrubbed will have these variables available to it, and
        environment variables are always available via
        <command>/proc/PID/environ</command>.
      </para>

      <para>
        This configuration parameter can be specified multiple times; once
        for each environment variable you wish to configure.
      </para>

      <variablelist>
        <varlistentry>
          <term>
            <option>lxc.environment</option>
          </term>
          <listitem>
            <para>
              Specify an environment variable to pass into the container.
              Example:
            </para>
            <programlisting>
              lxc.environment = APP_ENV=production
              lxc.environment = SYSLOG_SERVER=192.0.2.42
            </programlisting>
          </listitem>
        </varlistentry>
      </variablelist>
    </refsect2>

  </refsect1>

  <refsect1>
    <title>Examples</title>
      <para>
        In addition to the few examples given below, you will find
        some other examples of configuration file in @DOCDIR@/examples
      </para>
    <refsect2>
      <title>Network</title>
      <para>This configuration sets up a container to use a veth pair
        device with one side plugged to a bridge br0 (which has been
        configured before on the system by the administrator). The
        virtual network device visible in the container is renamed to
        eth0.</para>
      <programlisting>
        lxc.utsname = myhostname
        lxc.network.type = veth
        lxc.network.flags = up
        lxc.network.link = br0
        lxc.network.name = eth0
        lxc.network.hwaddr = 4a:49:43:49:79:bf
        lxc.network.ipv4 = 10.2.3.5/24 10.2.3.255
        lxc.network.ipv6 = 2003:db8:1:0:214:1234:fe0b:3597
      </programlisting>
    </refsect2>

    <refsect2>
      <title>UID/GID mapping</title>
      <para>This configuration will map both user and group ids in the
        range 0-9999 in the container to the ids 100000-109999 on the host.
      </para>
      <programlisting>
        lxc.id_map = u 0 100000 10000
        lxc.id_map = g 0 100000 10000
      </programlisting>
    </refsect2>

    <refsect2>
      <title>Control group</title>
      <para>This configuration will setup several control groups for
      the application, cpuset.cpus restricts usage of the defined cpu,
      cpus.share prioritize the control group, devices.allow makes
      usable the specified devices.</para>
      <programlisting>
        lxc.cgroup.cpuset.cpus = 0,1
        lxc.cgroup.cpu.shares = 1234
        lxc.cgroup.devices.deny = a
        lxc.cgroup.devices.allow = c 1:3 rw
        lxc.cgroup.devices.allow = b 8:0 rw
      </programlisting>
    </refsect2>

    <refsect2>
      <title>Complex configuration</title>
      <para>This example show a complex configuration making a complex
      network stack, using the control groups, setting a new hostname,
      mounting some locations and a changing root file system.</para>
      <programlisting>
        lxc.utsname = complex
        lxc.network.type = veth
        lxc.network.flags = up
        lxc.network.link = br0
        lxc.network.hwaddr = 4a:49:43:49:79:bf
        lxc.network.ipv4 = 10.2.3.5/24 10.2.3.255
        lxc.network.ipv6 = 2003:db8:1:0:214:1234:fe0b:3597
        lxc.network.ipv6 = 2003:db8:1:0:214:5432:feab:3588
        lxc.network.type = macvlan
        lxc.network.flags = up
        lxc.network.link = eth0
        lxc.network.hwaddr = 4a:49:43:49:79:bd
        lxc.network.ipv4 = 10.2.3.4/24
        lxc.network.ipv4 = 192.168.10.125/24
        lxc.network.ipv6 = 2003:db8:1:0:214:1234:fe0b:3596
        lxc.network.type = phys
        lxc.network.flags = up
        lxc.network.link = dummy0
        lxc.network.hwaddr = 4a:49:43:49:79:ff
        lxc.network.ipv4 = 10.2.3.6/24
        lxc.network.ipv6 = 2003:db8:1:0:214:1234:fe0b:3297
        lxc.cgroup.cpuset.cpus = 0,1
        lxc.cgroup.cpu.shares = 1234
        lxc.cgroup.devices.deny = a
        lxc.cgroup.devices.allow = c 1:3 rw
        lxc.cgroup.devices.allow = b 8:0 rw
        lxc.mount = /etc/fstab.complex
        lxc.mount.entry = /lib /root/myrootfs/lib none ro,bind 0 0
        lxc.rootfs = /mnt/rootfs.complex
        lxc.cap.drop = sys_module mknod setuid net_raw
        lxc.cap.drop = mac_override
      </programlisting>
    </refsect2>

  </refsect1>

  <refsect1>
    <title>See Also</title>
    <simpara>
      <citerefentry>
        <refentrytitle><command>chroot</command></refentrytitle>
        <manvolnum>1</manvolnum>
      </citerefentry>,

      <citerefentry>
        <refentrytitle><command>pivot_root</command></refentrytitle>
        <manvolnum>8</manvolnum>
      </citerefentry>,

      <citerefentry>
        <refentrytitle><filename>fstab</filename></refentrytitle>
        <manvolnum>5</manvolnum>
      </citerefentry>,

      <citerefentry>
        <refentrytitle><filename>capabilities</filename></refentrytitle>
        <manvolnum>7</manvolnum>
      </citerefentry>
    </simpara>
  </refsect1>

  &seealso;

  <refsect1>
    <title>Author</title>
    <para>Daniel Lezcano <email>daniel.lezcano@free.fr</email></para>
  </refsect1>

</refentry>

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