refactor AppArmor into LSM backend, add SELinux support

[mirror_lxc.git] / doc / lxc.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.conf</refentrytitle>
    <manvolnum>5</manvolnum>
  </refmeta>

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

    <refpurpose>
      linux 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 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>Stop signal</title>
      <para>
    Allows to specify signal name or number, sent by lxc-stop to
    shutdown the container. Different init systems could use
    different signals to perform clean shutdown sequence. Option
    allows signal to be specified in kill(1) fashion, e.g.
    SIGKILL, SIGRTMIN+14, SIGRTMAX-10 or plain number.
      </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>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>empty:</option> will create only the loopback
	      interface.
	    </para>

	    <para>
	      <option>veth:</option> a peer network device is created
	      with one side assigned to the container and the other
	      side is attached to a bridge specified by
	      the <option>lxc.network.link</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 setup before on the
	      system, <command>lxc</command> won't handle any
	      configuration outside of the container.  By
	      default <command>lxc</command> choose a name for the
	      network device belonging to the outside of the
	      container, this name is handled
	      by <command>lxc</command>, but if you wish to handle
	      this name yourself, you can tell <command>lxc</command>
	      to set a specific name with
	      the <option>lxc.network.veth.pair</option> option.
	    </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.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
	    </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</option>
	  </term>
	  <listitem>
	    <para>
	      Specify a path to a file where the console output will
	      be written. 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 does nothing with the container's
	<filename>/dev</filename>.  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. If the rootfs is an image file or a
	      block device and the fstab is used to mount a point
	      somewhere in this rootfs, the path of the rootfs mount
	      point should be prefixed with the
	      <filename>@LXCROOTFSMOUNT@</filename> default path or
	      the value of <option>lxc.rootfs.mount</option> if
	      specified. 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>

      </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>
	  </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.pivotdir</option>
	  </term>
	  <listitem>
	    <para>
	      where to pivot the original root file system under
	      <option>lxc.rootfs</option>, specified relatively to
	      that.  The default is <filename>mnt</filename>.
	      It is created if necessary, and also removed after
	      unmounting everything from it during container setup.
	    </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.
	    </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>
      </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.
      </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 = unconfined_u:unconfined_r:lxc_t:s0-s0:c0.c1023</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 should begin with a version number
	(which currently must be 1) on the first line, a policy type
	(which must be 'whitelist') on the second line, followed by a
	list of allowed system call numbers, one per line.
      </para>
      <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> Container name. </listitem>
	  <listitem> Section (always 'lxc'). </listitem>
	  <listitem> The hook type (i.e. 'clone' or 'pre-mount'). </listitem>
	  <listitem> Additional arguments In the
	  case of the clone hook, any extra arguments passed to
	  lxc-clone will appear as further arguments to the hook. </listitem>
	</itemizedlist>
	The following environment variables are set:
	<itemizedlist>
	  <listitem> LXC_NAME: is the container's name. </listitem>
	  <listitem> LXC_ROOTFS_MOUNT: the path to the mounted root filesystem. </listitem>
	  <listitem> LXC_CONFIG_FILE: the path to the container configuration file. </listitem>
	  <listitem> LXC_SRC_NAME: in the case of the clone hook, this is the original container's name. </listitem>
	  <listitem> LXC_ROOTFS_PATH: this is the lxc.rootfs enty for the container.  Note this is likely not where the mounted rootfs is to be found, use LXC_ROOTFS_MOUNT for that. </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 <refentrytitle><command>lxc-clone</command></refentrytitle>
	      <manvolnum>1</manvolnum> 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>

  </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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