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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 are in turn 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 overriden 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 file 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 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, 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. </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>Capability=</varname></term>

<term><varname>DropCapability=</varname></term>

<listitem><para>Takes a space separated list of Linux process

capabilities (see

<citerefentry><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 capabilites. 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>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 128bit 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>

</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, 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 mutiple 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>

</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, 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).</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>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>