systemd/man/systemd.nspawn.xml

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<refentry id="systemd.nspawn">

  <refentryinfo>
    <title>systemd.nspawn</title>
    <productname>systemd</productname>

    <authorgroup>
      <author>
        <contrib>Developer</contrib>
        <firstname>Lennart</firstname>
        <surname>Poettering</surname>
        <email>lennart@poettering.net</email>
      </author>
    </authorgroup>
  </refentryinfo>

  <refmeta>
    <refentrytitle>systemd.nspawn</refentrytitle>
    <manvolnum>5</manvolnum>
  </refmeta>

  <refnamediv>
    <refname>systemd.nspawn</refname>
    <refpurpose>Container settings</refpurpose>
  </refnamediv>

  <refsynopsisdiv>
    <para><filename>/etc/systemd/nspawn/<replaceable>machine</replaceable>.nspawn</filename></para>
    <para><filename>/run/systemd/nspawn/<replaceable>machine</replaceable>.nspawn</filename></para>
    <para><filename>/var/lib/machines/<replaceable>machine</replaceable>.nspawn</filename></para>
  </refsynopsisdiv>

  <refsect1>
    <title>Description</title>

    <para>An nspawn container settings file (suffix
    <filename>.nspawn</filename>) encodes additional runtime
    information about a local container, and is searched, read and
    used by
    <citerefentry><refentrytitle>systemd-nspawn</refentrytitle><manvolnum>1</manvolnum></citerefentry>
    when starting a container. Files of this type are named after the
    containers they define settings for. They are optional, and only
    required for containers whose execution environment shall differ
    from the defaults. Files of this type mostly contain settings that
    may also be set on the <command>systemd-nspawn</command> command
    line, and make it easier to persistently attach specific settings
    to specific containers. The syntax of these files is inspired by
    <filename>.desktop</filename> files following the <ulink
    url="http://standards.freedesktop.org/desktop-entry-spec/latest/">XDG
    Desktop Entry Specification</ulink>, which in turn are inspired by
    Microsoft Windows <filename>.ini</filename> files.</para>

    <para>Boolean arguments used in these settings files can be
    written in various formats. For positive settings, the strings
    <option>1</option>, <option>yes</option>, <option>true</option>
    and <option>on</option> are equivalent. For negative settings, the
    strings <option>0</option>, <option>no</option>,
    <option>false</option> and <option>off</option> are
    equivalent.</para>

    <para>Empty lines and lines starting with # or ; are
    ignored. This may be used for commenting. Lines ending
    in a backslash are concatenated with the following
    line while reading and the backslash is replaced by a
    space character. This may be used to wrap long lines.</para>

  </refsect1>

  <refsect1>
    <title><filename>.nspawn</filename> File Discovery</title>

    <para>Files are searched by appending the
    <filename>.nspawn</filename> suffix to the machine name of the
    container, as specified with the <option>--machine=</option>
    switch of <command>systemd-nspawn</command>, or derived from the
    directory or image file name. This file is first searched in
    <filename>/etc/systemd/nspawn/</filename> and
    <filename>/run/systemd/nspawn/</filename>. If found in these
    directories, its settings are read and all of them take full effect
    (but are possibly overridden by corresponding command line
    arguments). If not found, the file will then be searched next to
    the image file or in the immediate parent of the root directory of
    the container. If the file is found there, only a subset of the
    settings will take effect however. All settings that possibly
    elevate privileges or grant additional access to resources of the
    host (such as files or directories) are ignored. To which options
    this applies is documented below.</para>

    <para>Persistent settings files created and maintained by the
    administrator (and thus trusted) should be placed in
    <filename>/etc/systemd/nspawn/</filename>, while automatically
    downloaded (and thus potentially untrusted) settings files are
    placed in <filename>/var/lib/machines/</filename> instead (next to
    the container images), where their security impact is limited. In
    order to add privileged settings to <filename>.nspawn</filename>
    files acquired from the image vendor, it is recommended to copy the
    settings files into <filename>/etc/systemd/nspawn/</filename> and
    edit them there, so that the privileged options become
    available. The precise algorithm for how the files are searched and
    interpreted may be configured with
    <command>systemd-nspawn</command>'s <option>--settings=</option>
    switch, see
    <citerefentry><refentrytitle>systemd-nspawn</refentrytitle><manvolnum>1</manvolnum></citerefentry>
    for details.</para>
  </refsect1>

  <refsect1>
    <title>[Exec] Section Options</title>

    <para>Settings files may include an <literal>[Exec]</literal>
    section, which carries various execution parameters:</para>

    <variablelist>

      <varlistentry>
        <term><varname>Boot=</varname></term>

        <listitem><para>Takes a boolean argument, which defaults to off. If enabled, <command>systemd-nspawn</command>
        will automatically search for an <filename>init</filename> executable and invoke it. In this case, the
        specified parameters using <varname>Parameters=</varname> are passed as additional arguments to the
        <filename>init</filename> process. This setting corresponds to the <option>--boot</option> switch on the
        <command>systemd-nspawn</command> command line. This option may not be combined with
        <varname>ProcessTwo=yes</varname>. This option is the default if the
        <filename>systemd-nspawn@.service</filename> template unit file is used.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>ProcessTwo=</varname></term>

        <listitem><para>Takes a boolean argument, which defaults to off. If enabled, the specified program is run as
        PID 2. A stub init process is run as PID 1. This setting corresponds to the <option>--as-pid2</option> switch
        on the <command>systemd-nspawn</command> command line. This option may not be combined with
        <varname>Boot=yes</varname>.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>Parameters=</varname></term>

        <listitem><para>Takes a space-separated list of
        arguments. This is either a command line, beginning with the
        binary name to execute, or – if <varname>Boot=</varname> is
        enabled – the list of arguments to pass to the init
        process. This setting corresponds to the command line
        parameters passed on the <command>systemd-nspawn</command>
        command line.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>Environment=</varname></term>

        <listitem><para>Takes an environment variable assignment
        consisting of key and value, separated by
        <literal>=</literal>. Sets an environment variable for the
        main process invoked in the container. This setting may be
        used multiple times to set multiple environment variables. It
        corresponds to the <option>--setenv=</option> command line
        switch.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>User=</varname></term>

        <listitem><para>Takes a UNIX user name. Specifies the user
        name to invoke the main process of the container as. This user
        must be known in the container's user database. This
        corresponds to the <option>--user=</option> command line
        switch.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>WorkingDirectory=</varname></term>

        <listitem><para>Selects the working directory for the process invoked in the container. Expects an absolute
        path in the container's file system namespace. This corresponds to the <option>--chdir=</option> command line
        switch.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>PivotRoot=</varname></term>

        <listitem><para>Selects a directory to pivot to <filename>/</filename> inside the container when starting up.
        Takes a single path, or a pair of two paths separated by a colon. Both paths must be absolute, and are resolved
        in the container's file system namespace. This corresponds to the <option>--pivot-root=</option> command line
        switch.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>Capability=</varname></term>
        <term><varname>DropCapability=</varname></term>

        <listitem><para>Takes a space-separated list of Linux process
        capabilities (see
        <citerefentry project='man-pages'><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
        for details). The <varname>Capability=</varname> setting
        specifies additional capabilities to pass on top of the
        default set of capabilities. The
        <varname>DropCapability=</varname> setting specifies
        capabilities to drop from the default set. These settings
        correspond to the <option>--capability=</option> and
        <option>--drop-capability=</option> command line
        switches. Note that <varname>Capability=</varname> is a
        privileged setting, and only takes effect in
        <filename>.nspawn</filename> files in
        <filename>/etc/systemd/nspawn/</filename> and
        <filename>/run/system/nspawn/</filename> (see above). On the
        other hand, <varname>DropCapability=</varname> takes effect in
        all cases.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>KillSignal=</varname></term>

        <listitem><para>Specify the process signal to send to the
        container's PID 1 when nspawn itself receives SIGTERM, in
        order to trigger an orderly shutdown of the container.
        Defaults to SIGRTMIN+3 if <option>Boot=</option> is used
        (on systemd-compatible init systems SIGRTMIN+3 triggers an
        orderly shutdown). For a list of valid signals, see
        <citerefentry project='man-pages'><refentrytitle>signal</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>Personality=</varname></term>

        <listitem><para>Configures the kernel personality for the
        container. This is equivalent to the
        <option>--personality=</option> switch.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>MachineID=</varname></term>

        <listitem><para>Configures the 128-bit machine ID (UUID) to pass to
        the container. This is equivalent to the
        <option>--uuid=</option> command line switch. This option is
        privileged (see above). </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>PrivateUsers=</varname></term>

        <listitem><para>Configures support for usernamespacing. This is equivalent to the
        <option>--private-users=</option> command line switch, and takes the same options. This option is privileged
        (see above). This option is the default if the <filename>systemd-nspawn@.service</filename> template unit file
        is used.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>NotifyReady=</varname></term>

        <listitem><para>Configures support for notifications from the container's init process.  This is equivalent to
        the <option>--notify-ready=</option> command line switch, and takes the same parameters. See
        <citerefentry><refentrytitle>systemd-nspawn</refentrytitle><manvolnum>1</manvolnum></citerefentry> for details
        about the specific options supported.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>SystemCallFilter=</varname></term>

        <listitem><para>Configures the system call filter applied to containers. This is equivalent to the
        <option>--system-call-filter=</option> command line switch, and takes the same list parameter. See
        <citerefentry><refentrytitle>systemd-nspawn</refentrytitle><manvolnum>1</manvolnum></citerefentry> for
        details.</para></listitem>
      </varlistentry>

    </variablelist>
  </refsect1>

  <refsect1>
    <title>[Files] Section Options</title>

    <para>Settings files may include a <literal>[Files]</literal>
    section, which carries various parameters configuring the file
    system of the container:</para>

    <variablelist>

      <varlistentry>
        <term><varname>ReadOnly=</varname></term>

        <listitem><para>Takes a boolean argument, which defaults to off. If
        specified, the container will be run with a read-only file
        system. This setting corresponds to the
        <option>--read-only</option> command line
        switch.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>Volatile=</varname></term>

        <listitem><para>Takes a boolean argument, or the special value
        <literal>state</literal>. This configures whether to run the
        container with volatile state and/or configuration. This
        option is equivalent to <option>--volatile=</option>, see
        <citerefentry><refentrytitle>systemd-nspawn</refentrytitle><manvolnum>1</manvolnum></citerefentry>
        for details about the specific options
        supported.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>Bind=</varname></term>
        <term><varname>BindReadOnly=</varname></term>

        <listitem><para>Adds a bind mount from the host into the
        container. Takes a single path, a pair of two paths separated
        by a colon, or a triplet of two paths plus an option string
        separated by colons. This option may be used multiple times to
        configure multiple bind mounts. This option is equivalent to
        the command line switches <option>--bind=</option> and
        <option>--bind-ro=</option>, see
        <citerefentry><refentrytitle>systemd-nspawn</refentrytitle><manvolnum>1</manvolnum></citerefentry>
        for details about the specific options supported. This setting
        is privileged (see above).</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>TemporaryFileSystem=</varname></term>

        <listitem><para>Adds a <literal>tmpfs</literal> mount to the
        container. Takes a path or a pair of path and option string,
        separated by a colon. This option may be used multiple times to
        configure multiple <literal>tmpfs</literal> mounts. This
        option is equivalent to the command line switch
        <option>--tmpfs=</option>, see
        <citerefentry><refentrytitle>systemd-nspawn</refentrytitle><manvolnum>1</manvolnum></citerefentry>
        for details about the specific options supported. This setting
        is privileged (see above).</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>Overlay=</varname></term>
        <term><varname>OverlayReadOnly=</varname></term>

        <listitem><para>Adds an overlay mount point. Takes a colon-separated list of paths.  This option may be used
        multiple times to configure multiple overlay mounts. This option is equivalent to the command line switches
        <option>--overlay=</option> and <option>--overlay-ro=</option>, see
        <citerefentry><refentrytitle>systemd-nspawn</refentrytitle><manvolnum>1</manvolnum></citerefentry> for details
        about the specific options supported. This setting is privileged (see above).</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>PrivateUsersChown=</varname></term>

        <listitem><para>Configures whether the ownership of the files and directories in the container tree shall be
        adjusted to the UID/GID range used, if necessary and user namespacing is enabled. This is equivalent to the
        <option>--private-users-chown</option> command line switch. This option is privileged (see
        above). </para></listitem>
      </varlistentry>

    </variablelist>
  </refsect1>

  <refsect1>
    <title>[Network] Section Options</title>

    <para>Settings files may include a <literal>[Network]</literal>
    section, which carries various parameters configuring the network
    connectivity of the container:</para>

    <variablelist>

      <varlistentry>
        <term><varname>Private=</varname></term>

        <listitem><para>Takes a boolean argument, which defaults to off. If
        enabled, the container will run in its own network namespace
        and not share network interfaces and configuration with the
        host. This setting corresponds to the
        <option>--private-network</option> command line
        switch.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>VirtualEthernet=</varname></term>

        <listitem><para>Takes a boolean argument. Configures whether to create a virtual Ethernet connection
        (<literal>veth</literal>) between host and the container. This setting implies
        <varname>Private=yes</varname>. This setting corresponds to the <option>--network-veth</option> command line
        switch. This option is privileged (see above). This option is the default if the
        <filename>systemd-nspawn@.service</filename> template unit file is used.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>VirtualEthernetExtra=</varname></term>

        <listitem><para>Takes a colon-separated pair of interface
        names. Configures an additional virtual Ethernet connection
        (<literal>veth</literal>) between host and the container. The
        first specified name is the interface name on the host, the
        second the interface name in the container. The latter may be
        omitted in which case it is set to the same name as the host
        side interface. This setting implies
        <varname>Private=yes</varname>. This setting corresponds to
        the <option>--network-veth-extra=</option> command line
        switch, and maybe be used multiple times. It is independent of
        <varname>VirtualEthernet=</varname>. This option is privileged
        (see above).</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>Interface=</varname></term>

        <listitem><para>Takes a space-separated list of interfaces to
        add to the container. This option corresponds to the
        <option>--network-interface=</option> command line switch and
        implies <varname>Private=yes</varname>. This option is
        privileged (see above).</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>MACVLAN=</varname></term>
        <term><varname>IPVLAN=</varname></term>

        <listitem><para>Takes a space-separated list of interfaces to
        add MACLVAN or IPVLAN interfaces to, which are then added to
        the container. These options correspond to the
        <option>--network-macvlan=</option> and
        <option>--network-ipvlan=</option> command line switches and
        imply <varname>Private=yes</varname>. These options are
        privileged (see above).</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>Bridge=</varname></term>

        <listitem><para>Takes an interface name. This setting implies
        <varname>VirtualEthernet=yes</varname> and
        <varname>Private=yes</varname> and has the effect that the
        host side of the created virtual Ethernet link is connected to
        the specified bridge interface. This option corresponds to the
        <option>--network-bridge=</option> command line switch. This
        option is privileged (see above).</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>Zone=</varname></term>

        <listitem><para>Takes a network zone name. This setting implies <varname>VirtualEthernet=yes</varname> and
        <varname>Private=yes</varname> and has the effect that the host side of the created virtual Ethernet link is
        connected to an automatically managed bridge interface named after the passed argument, prefixed with
        <literal>vz-</literal>. This option corresponds to the <option>--network-zone=</option> command line
        switch. This option is privileged (see above).</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>Port=</varname></term>

        <listitem><para>Exposes a TCP or UDP port of the container on
        the host. This option corresponds to the
        <option>--port=</option> command line switch, see
        <citerefentry><refentrytitle>systemd-nspawn</refentrytitle><manvolnum>1</manvolnum></citerefentry>
        for the precise syntax of the argument this option takes. This
        option is privileged (see above).</para></listitem>
      </varlistentry>
    </variablelist>
  </refsect1>

  <refsect1>
    <title>See Also</title>
    <para>
      <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>systemd-nspawn</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>
    </para>
  </refsect1>

</refentry>