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1544 lines
91 KiB
XML
1544 lines
91 KiB
XML
<?xml version='1.0'?>
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd" [
|
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<!ENTITY fedora_latest_version "32">
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<!ENTITY fedora_cloud_release "1.6">
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]>
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<!-- SPDX-License-Identifier: LGPL-2.1+ -->
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||
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<refentry id="systemd-nspawn"
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||
xmlns:xi="http://www.w3.org/2001/XInclude">
|
||
|
||
<refentryinfo>
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||
<title>systemd-nspawn</title>
|
||
<productname>systemd</productname>
|
||
</refentryinfo>
|
||
|
||
<refmeta>
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||
<refentrytitle>systemd-nspawn</refentrytitle>
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||
<manvolnum>1</manvolnum>
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||
</refmeta>
|
||
|
||
<refnamediv>
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||
<refname>systemd-nspawn</refname>
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||
<refpurpose>Spawn a command or OS in a light-weight container</refpurpose>
|
||
</refnamediv>
|
||
|
||
<refsynopsisdiv>
|
||
<cmdsynopsis>
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||
<command>systemd-nspawn</command>
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||
<arg choice="opt" rep="repeat">OPTIONS</arg>
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||
<arg choice="opt"><replaceable>COMMAND</replaceable>
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||
<arg choice="opt" rep="repeat">ARGS</arg>
|
||
</arg>
|
||
</cmdsynopsis>
|
||
<cmdsynopsis>
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||
<command>systemd-nspawn</command>
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||
<arg choice="plain">--boot</arg>
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||
<arg choice="opt" rep="repeat">OPTIONS</arg>
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||
<arg choice="opt" rep="repeat">ARGS</arg>
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||
</cmdsynopsis>
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||
</refsynopsisdiv>
|
||
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||
<refsect1>
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||
<title>Description</title>
|
||
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||
<para><command>systemd-nspawn</command> may be used to run a command or OS in a light-weight namespace
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||
container. In many ways it is similar to <citerefentry
|
||
project='man-pages'><refentrytitle>chroot</refentrytitle><manvolnum>1</manvolnum></citerefentry>, but more powerful
|
||
since it fully virtualizes the file system hierarchy, as well as the process tree, the various IPC subsystems and
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||
the host and domain name.</para>
|
||
|
||
<para><command>systemd-nspawn</command> may be invoked on any directory tree containing an operating system tree,
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||
using the <option>--directory=</option> command line option. By using the <option>--machine=</option> option an OS
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||
tree is automatically searched for in a couple of locations, most importantly in
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||
<filename>/var/lib/machines</filename>, the suggested directory to place OS container images installed on the
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||
system.</para>
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||
|
||
<para>In contrast to <citerefentry
|
||
project='man-pages'><refentrytitle>chroot</refentrytitle><manvolnum>1</manvolnum></citerefentry> <command>systemd-nspawn</command>
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||
may be used to boot full Linux-based operating systems in a container.</para>
|
||
|
||
<para><command>systemd-nspawn</command> limits access to various kernel interfaces in the container to read-only,
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||
such as <filename>/sys</filename>, <filename>/proc/sys</filename> or <filename>/sys/fs/selinux</filename>. The
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||
host's network interfaces and the system clock may not be changed from within the container. Device nodes may not
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||
be created. The host system cannot be rebooted and kernel modules may not be loaded from within the
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||
container.</para>
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||
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||
<para>Use a tool like <citerefentry
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||
project='mankier'><refentrytitle>dnf</refentrytitle><manvolnum>8</manvolnum></citerefentry>, <citerefentry
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||
project='die-net'><refentrytitle>debootstrap</refentrytitle><manvolnum>8</manvolnum></citerefentry>, or
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||
<citerefentry project='archlinux'><refentrytitle>pacman</refentrytitle><manvolnum>8</manvolnum></citerefentry> to
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||
set up an OS directory tree suitable as file system hierarchy for <command>systemd-nspawn</command> containers. See
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the Examples section below for details on suitable invocation of these commands.</para>
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||
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||
<para>As a safety check <command>systemd-nspawn</command> will verify the existence of
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<filename>/usr/lib/os-release</filename> or <filename>/etc/os-release</filename> in the container tree before
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||
starting the container (see
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||
<citerefentry><refentrytitle>os-release</refentrytitle><manvolnum>5</manvolnum></citerefentry>). It might be
|
||
necessary to add this file to the container tree manually if the OS of the container is too old to contain this
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||
file out-of-the-box.</para>
|
||
|
||
<para><command>systemd-nspawn</command> may be invoked directly from the interactive command line or run as system
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||
service in the background. In this mode each container instance runs as its own service instance; a default
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||
template unit file <filename>systemd-nspawn@.service</filename> is provided to make this easy, taking the container
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||
name as instance identifier. Note that different default options apply when <command>systemd-nspawn</command> is
|
||
invoked by the template unit file than interactively on the command line. Most importantly the template unit file
|
||
makes use of the <option>--boot</option> which is not the default in case <command>systemd-nspawn</command> is
|
||
invoked from the interactive command line. Further differences with the defaults are documented along with the
|
||
various supported options below.</para>
|
||
|
||
<para>The <citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry> tool may
|
||
be used to execute a number of operations on containers. In particular it provides easy-to-use commands to run
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||
containers as system services using the <filename>systemd-nspawn@.service</filename> template unit
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||
file.</para>
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||
|
||
<para>Along with each container a settings file with the <filename>.nspawn</filename> suffix may exist, containing
|
||
additional settings to apply when running the container. See
|
||
<citerefentry><refentrytitle>systemd.nspawn</refentrytitle><manvolnum>5</manvolnum></citerefentry> for
|
||
details. Settings files override the default options used by the <filename>systemd-nspawn@.service</filename>
|
||
template unit file, making it usually unnecessary to alter this template file directly.</para>
|
||
|
||
<para>Note that <command>systemd-nspawn</command> will mount file systems private to the container to
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||
<filename>/dev</filename>, <filename>/run</filename> and similar. These will not be visible outside of the
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||
container, and their contents will be lost when the container exits.</para>
|
||
|
||
<para>Note that running two <command>systemd-nspawn</command> containers from the same directory tree will not make
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||
processes in them see each other. The PID namespace separation of the two containers is complete and the containers
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||
will share very few runtime objects except for the underlying file system. Use
|
||
<citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>'s
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||
<command>login</command> or <command>shell</command> commands to request an additional login session in a running
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||
container.</para>
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||
|
||
<para><command>systemd-nspawn</command> implements the <ulink
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||
url="https://systemd.io/CONTAINER_INTERFACE">Container Interface</ulink> specification.</para>
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||
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||
<para>While running, containers invoked with <command>systemd-nspawn</command> are registered with the
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||
<citerefentry><refentrytitle>systemd-machined</refentrytitle><manvolnum>8</manvolnum></citerefentry> service that
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||
keeps track of running containers, and provides programming interfaces to interact with them.</para>
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||
</refsect1>
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||
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||
<refsect1>
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||
<title>Options</title>
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||
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||
<para>If option <option>-b</option> is specified, the arguments
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||
are used as arguments for the init program. Otherwise,
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||
<replaceable>COMMAND</replaceable> specifies the program to launch
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||
in the container, and the remaining arguments are used as
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||
arguments for this program. If <option>--boot</option> is not used and
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no arguments are specified, a shell is launched in the
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container.</para>
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<para>The following options are understood:</para>
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<variablelist>
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||
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<varlistentry>
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<term><option>-q</option></term>
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<term><option>--quiet</option></term>
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||
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||
<listitem><para>Turns off any status output by the tool
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||
itself. When this switch is used, the only output from nspawn
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||
will be the console output of the container OS
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itself.</para></listitem>
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||
</varlistentry>
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||
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||
<varlistentry>
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<term><option>--settings=</option><replaceable>MODE</replaceable></term>
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<listitem><para>Controls whether
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<command>systemd-nspawn</command> shall search for and use
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additional per-container settings from
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<filename>.nspawn</filename> files. Takes a boolean or the
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special values <option>override</option> or
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||
<option>trusted</option>.</para>
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||
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||
<para>If enabled (the default), a settings file named after the
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machine (as specified with the <option>--machine=</option>
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setting, or derived from the directory or image file name)
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||
with the suffix <filename>.nspawn</filename> is searched in
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<filename>/etc/systemd/nspawn/</filename> and
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<filename>/run/systemd/nspawn/</filename>. If it is found
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||
there, its settings are read and used. If it is not found
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there, it is subsequently searched in the same directory as the
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||
image file or in the immediate parent of the root directory of
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the container. In this case, if the file is found, its settings
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||
will be also read and used, but potentially unsafe settings
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||
are ignored. Note that in both these cases, settings on the
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||
command line take precedence over the corresponding settings
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||
from loaded <filename>.nspawn</filename> files, if both are
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||
specified. Unsafe settings are considered all settings that
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||
elevate the container's privileges or grant access to
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||
additional resources such as files or directories of the
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||
host. For details about the format and contents of
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||
<filename>.nspawn</filename> files, consult
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||
<citerefentry><refentrytitle>systemd.nspawn</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
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||
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||
<para>If this option is set to <option>override</option>, the
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||
file is searched, read and used the same way, however, the order of
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||
precedence is reversed: settings read from the
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||
<filename>.nspawn</filename> file will take precedence over
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||
the corresponding command line options, if both are
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||
specified.</para>
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||
|
||
<para>If this option is set to <option>trusted</option>, the
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||
file is searched, read and used the same way, but regardless
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||
of being found in <filename>/etc/systemd/nspawn/</filename>,
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||
<filename>/run/systemd/nspawn/</filename> or next to the image
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||
file or container root directory, all settings will take
|
||
effect, however, command line arguments still take precedence
|
||
over corresponding settings.</para>
|
||
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||
<para>If disabled, no <filename>.nspawn</filename> file is read
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||
and no settings except the ones on the command line are in
|
||
effect.</para></listitem>
|
||
</varlistentry>
|
||
|
||
</variablelist>
|
||
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||
<refsect2>
|
||
<title>Image Options</title>
|
||
|
||
<variablelist>
|
||
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||
<varlistentry>
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||
<term><option>-D</option></term>
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||
<term><option>--directory=</option></term>
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||
|
||
<listitem><para>Directory to use as file system root for the
|
||
container.</para>
|
||
|
||
<para>If neither <option>--directory=</option>, nor
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||
<option>--image=</option> is specified the directory is
|
||
determined by searching for a directory named the same as the
|
||
machine name specified with <option>--machine=</option>. See
|
||
<citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
|
||
section "Files and Directories" for the precise search path.</para>
|
||
|
||
<para>If neither <option>--directory=</option>,
|
||
<option>--image=</option>, nor <option>--machine=</option>
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||
are specified, the current directory will
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||
be used. May not be specified together with
|
||
<option>--image=</option>.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
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||
<term><option>--template=</option></term>
|
||
|
||
<listitem><para>Directory or <literal>btrfs</literal> subvolume to use as template for the
|
||
container's root directory. If this is specified and the container's root directory (as configured by
|
||
<option>--directory=</option>) does not yet exist it is created as <literal>btrfs</literal> snapshot
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||
(if supported) or plain directory (otherwise) and populated from this template tree. Ideally, the
|
||
specified template path refers to the root of a <literal>btrfs</literal> subvolume, in which case a
|
||
simple copy-on-write snapshot is taken, and populating the root directory is instant. If the
|
||
specified template path does not refer to the root of a <literal>btrfs</literal> subvolume (or not
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||
even to a <literal>btrfs</literal> file system at all), the tree is copied (though possibly in a
|
||
'reflink' copy-on-write scheme — if the file system supports that), which can be substantially more
|
||
time-consuming. Note that the snapshot taken is of the specified directory or subvolume, including
|
||
all subdirectories and subvolumes below it, but excluding any sub-mounts. May not be specified
|
||
together with <option>--image=</option> or <option>--ephemeral</option>.</para>
|
||
|
||
<para>Note that this switch leaves hostname, machine ID and
|
||
all other settings that could identify the instance
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||
unmodified.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><option>-x</option></term>
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||
<term><option>--ephemeral</option></term>
|
||
|
||
<listitem><para>If specified, the container is run with a temporary snapshot of its file system that is removed
|
||
immediately when the container terminates. May not be specified together with
|
||
<option>--template=</option>.</para>
|
||
<para>Note that this switch leaves hostname, machine ID and all other settings that could identify
|
||
the instance unmodified. Please note that — as with <option>--template=</option> — taking the
|
||
temporary snapshot is more efficient on file systems that support subvolume snapshots or 'reflinks'
|
||
natively (<literal>btrfs</literal> or new <literal>xfs</literal>) than on more traditional file
|
||
systems that do not (<literal>ext4</literal>). Note that the snapshot taken is of the specified
|
||
directory or subvolume, including all subdirectories and subvolumes below it, but excluding any
|
||
sub-mounts.</para>
|
||
|
||
<para>With this option no modifications of the container image are retained. Use
|
||
<option>--volatile=</option> (described below) for other mechanisms to restrict persistency of
|
||
container images during runtime.</para>
|
||
</listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><option>-i</option></term>
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||
<term><option>--image=</option></term>
|
||
|
||
<listitem><para>Disk image to mount the root directory for the
|
||
container from. Takes a path to a regular file or to a block
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||
device node. The file or block device must contain
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||
either:</para>
|
||
|
||
<itemizedlist>
|
||
<listitem><para>An MBR partition table with a single
|
||
partition of type 0x83 that is marked
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||
bootable.</para></listitem>
|
||
|
||
<listitem><para>A GUID partition table (GPT) with a single
|
||
partition of type
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||
0fc63daf-8483-4772-8e79-3d69d8477de4.</para></listitem>
|
||
|
||
<listitem><para>A GUID partition table (GPT) with a marked
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||
root partition which is mounted as the root directory of the
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||
container. Optionally, GPT images may contain a home and/or
|
||
a server data partition which are mounted to the appropriate
|
||
places in the container. All these partitions must be
|
||
identified by the partition types defined by the <ulink
|
||
url="https://systemd.io/DISCOVERABLE_PARTITIONS">Discoverable
|
||
Partitions Specification</ulink>.</para></listitem>
|
||
|
||
<listitem><para>No partition table, and a single file system spanning the whole image.</para></listitem>
|
||
</itemizedlist>
|
||
|
||
<para>On GPT images, if an EFI System Partition (ESP) is discovered, it is automatically mounted to
|
||
<filename>/efi</filename> (or <filename>/boot</filename> as fallback) in case a directory by this name exists
|
||
and is empty.</para>
|
||
|
||
<para>Partitions encrypted with LUKS are automatically decrypted. Also, on GPT images dm-verity data integrity
|
||
hash partitions are set up if the root hash for them is specified using the <option>--root-hash=</option>
|
||
option.</para>
|
||
|
||
<para>Single file system images (i.e. file systems without a surrounding partition table) can be opened using
|
||
dm-verity if the integrity data is passed using the <option>--root-hash=</option> and
|
||
<option>--verity-data=</option> (and optionally <option>--root-hash-sig=</option>) options.</para>
|
||
|
||
<para>Any other partitions, such as foreign partitions or swap partitions are not mounted. May not be specified
|
||
together with <option>--directory=</option>, <option>--template=</option>.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><option>--oci-bundle=</option></term>
|
||
|
||
<listitem><para>Takes the path to an OCI runtime bundle to invoke, as specified in the <ulink
|
||
url="https://github.com/opencontainers/runtime-spec/blob/master/spec.md">OCI Runtime Specification</ulink>. In
|
||
this case no <filename>.nspawn</filename> file is loaded, and the root directory and various settings are read
|
||
from the OCI runtime JSON data (but data passed on the command line takes precedence).</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><option>--read-only</option></term>
|
||
|
||
<listitem><para>Mount the container's root file system (and any other file systems container in the container
|
||
image) read-only. This has no effect on additional mounts made with <option>--bind=</option>,
|
||
<option>--tmpfs=</option> and similar options. This mode is implied if the container image file or directory is
|
||
marked read-only itself. It is also implied if <option>--volatile=</option> is used. In this case the container
|
||
image on disk is strictly read-only, while changes are permitted but kept non-persistently in memory only. For
|
||
further details, see below.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><option>--volatile</option></term>
|
||
<term><option>--volatile=</option><replaceable>MODE</replaceable></term>
|
||
|
||
<listitem><para>Boots the container in volatile mode. When no mode parameter is passed or when mode is
|
||
specified as <option>yes</option>, full volatile mode is enabled. This means the root directory is mounted as a
|
||
mostly unpopulated <literal>tmpfs</literal> instance, and <filename>/usr/</filename> from the OS tree is
|
||
mounted into it in read-only mode (the system thus starts up with read-only OS image, but pristine state and
|
||
configuration, any changes are lost on shutdown). When the mode parameter is specified as
|
||
<option>state</option>, the OS tree is mounted read-only, but <filename>/var/</filename> is mounted as a
|
||
writable <literal>tmpfs</literal> instance into it (the system thus starts up with read-only OS resources and
|
||
configuration, but pristine state, and any changes to the latter are lost on shutdown). When the mode parameter
|
||
is specified as <option>overlay</option> the read-only root file system is combined with a writable
|
||
<filename>tmpfs</filename> instance through <literal>overlayfs</literal>, so that it appears at it normally
|
||
would, but any changes are applied to the temporary file system only and lost when the container is
|
||
terminated. When the mode parameter is specified as <option>no</option> (the default), the whole OS tree is
|
||
made available writable (unless <option>--read-only</option> is specified, see above).</para>
|
||
|
||
<para>Note that if one of the volatile modes is chosen, its effect is limited to the root file system (or
|
||
<filename>/var/</filename> in case of <option>state</option>), and any other mounts placed in the hierarchy are
|
||
unaffected — regardless if they are established automatically (e.g. the EFI system partition that might be
|
||
mounted to <filename>/efi/</filename> or <filename>/boot/</filename>) or explicitly (e.g. through an additional
|
||
command line option such as <option>--bind=</option>, see below). This means, even if
|
||
<option>--volatile=overlay</option> is used changes to <filename>/efi/</filename> or
|
||
<filename>/boot/</filename> are prohibited in case such a partition exists in the container image operated on,
|
||
and even if <option>--volatile=state</option> is used the hypothetical file <filename>/etc/foobar</filename> is
|
||
potentially writable if <option>--bind=/etc/foobar</option> if used to mount it from outside the read-only
|
||
container <filename>/etc</filename> directory.</para>
|
||
|
||
<para>The <option>--ephemeral</option> option is closely related to this setting, and provides similar
|
||
behaviour by making a temporary, ephemeral copy of the whole OS image and executing that. For further details,
|
||
see above.</para>
|
||
|
||
<para>The <option>--tmpfs=</option> and <option>--overlay=</option> options provide similar functionality, but
|
||
for specific sub-directories of the OS image only. For details, see below.</para>
|
||
|
||
<para>This option provides similar functionality for containers as the <literal>systemd.volatile=</literal>
|
||
kernel command line switch provides for host systems. See
|
||
<citerefentry><refentrytitle>kernel-command-line</refentrytitle><manvolnum>7</manvolnum></citerefentry> for
|
||
details.</para>
|
||
|
||
<para>Note that setting this option to <option>yes</option> or <option>state</option> will only work
|
||
correctly with operating systems in the container that can boot up with only
|
||
<filename>/usr/</filename> mounted, and are able to automatically populate <filename>/var/</filename>
|
||
(and <filename>/etc/</filename> in case of <literal>--volatile=yes</literal>). Specifically, this
|
||
means that operating systems that follow the historic split of <filename>/bin/</filename> and
|
||
<filename>/lib/</filename> (and related directories) from <filename>/usr/</filename> (i.e. where the
|
||
former are not symlinks into the latter) are not supported by <literal>--volatile=yes</literal> as
|
||
container payload. The <option>overlay</option> option does not require any particular preparations
|
||
in the OS, but do note that <literal>overlayfs</literal> behaviour differs from regular file systems
|
||
in a number of ways, and hence compatibility is limited.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><option>--root-hash=</option></term>
|
||
|
||
<listitem><para>Takes a data integrity (dm-verity) root hash specified in hexadecimal. This option enables data
|
||
integrity checks using dm-verity, if the used image contains the appropriate integrity data (see above). The
|
||
specified hash must match the root hash of integrity data, and is usually at least 256 bits (and hence 64
|
||
formatted hexadecimal characters) long (in case of SHA256 for example). If this option is not specified, but
|
||
the image file carries the <literal>user.verity.roothash</literal> extended file attribute (see <citerefentry
|
||
project='man-pages'><refentrytitle>xattr</refentrytitle><manvolnum>7</manvolnum></citerefentry>), then the root
|
||
hash is read from it, also as formatted hexadecimal characters. If the extended file attribute is not found (or
|
||
is not supported by the underlying file system), but a file with the <filename>.roothash</filename> suffix is
|
||
found next to the image file, bearing otherwise the same name (except if the image has the
|
||
<filename>.raw</filename> suffix, in which case the root hash file must not have it in its name), the root hash
|
||
is read from it and automatically used, also as formatted hexadecimal characters.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><option>--root-hash-sig=</option></term>
|
||
|
||
<listitem><para>Takes a PKCS7 formatted binary signature of the <option>--root-hash=</option> option as a path
|
||
to a DER encoded signature file or as an ASCII base64 string encoding of the DER encoded signature, prefixed
|
||
by <literal>base64:</literal>. The dm-verity volume will only be opened if the signature of the root hash hex
|
||
string is valid and done by a public key present in the kernel keyring. If this option is not specified, but a
|
||
file with the <filename>.roothash.p7s</filename> suffix is found next to the image file, bearing otherwise the
|
||
same name (except if the image has the <filename>.raw</filename> suffix, in which case the signature file must
|
||
not have it in its name), the signature is read from it and automatically used.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><option>--verity-data=</option></term>
|
||
|
||
<listitem><para>Takes the path to a data integrity (dm-verity) file. This option enables data integrity checks
|
||
using dm-verity, if a root-hash is passed and if the used image itself does not contains the integrity data.
|
||
The integrity data must be matched by the root hash. If this option is not specified, but a file with the
|
||
<filename>.verity</filename> suffix is found next to the image file, bearing otherwise the same name (except if
|
||
the image has the <filename>.raw</filename> suffix, in which case the verity data file must not have it in its name),
|
||
the verity data is read from it and automatically used.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><option>--pivot-root=</option></term>
|
||
|
||
<listitem><para>Pivot the specified directory to <filename>/</filename> inside the container, and either unmount the
|
||
container's old root, or pivot it to another specified directory. Takes one of: a path argument — in which case the
|
||
specified path will be pivoted to <filename>/</filename> and the old root will be unmounted; or a colon-separated pair
|
||
of new root path and pivot destination for the old root. The new root path will be pivoted to <filename>/</filename>,
|
||
and the old <filename>/</filename> will be pivoted to the other directory. Both paths must be absolute, and are resolved
|
||
in the container's file system namespace.</para>
|
||
|
||
<para>This is for containers which have several bootable directories in them; for example, several
|
||
<ulink url="https://ostree.readthedocs.io/en/latest/">OSTree</ulink> deployments. It emulates the behavior of
|
||
the boot loader and initial RAM disk which normally select which directory to mount as the root and start the
|
||
container's PID 1 in.</para></listitem>
|
||
</varlistentry>
|
||
</variablelist>
|
||
|
||
</refsect2><refsect2>
|
||
<title>Execution Options</title>
|
||
|
||
<variablelist>
|
||
<varlistentry>
|
||
<term><option>-a</option></term>
|
||
<term><option>--as-pid2</option></term>
|
||
|
||
<listitem><para>Invoke the shell or specified program as process ID (PID) 2 instead of PID 1 (init). By
|
||
default, if neither this option nor <option>--boot</option> is used, the selected program is run as the process
|
||
with PID 1, a mode only suitable for programs that are aware of the special semantics that the process with
|
||
PID 1 has on UNIX. For example, it needs to reap all processes reparented to it, and should implement
|
||
<command>sysvinit</command> compatible signal handling (specifically: it needs to reboot on SIGINT, reexecute
|
||
on SIGTERM, reload configuration on SIGHUP, and so on). With <option>--as-pid2</option> a minimal stub init
|
||
process is run as PID 1 and the selected program is executed as PID 2 (and hence does not need to implement any
|
||
special semantics). The stub init process will reap processes as necessary and react appropriately to
|
||
signals. It is recommended to use this mode to invoke arbitrary commands in containers, unless they have been
|
||
modified to run correctly as PID 1. Or in other words: this switch should be used for pretty much all commands,
|
||
except when the command refers to an init or shell implementation, as these are generally capable of running
|
||
correctly as PID 1. This option may not be combined with <option>--boot</option>.</para>
|
||
</listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><option>-b</option></term>
|
||
<term><option>--boot</option></term>
|
||
|
||
<listitem><para>Automatically search for an init program and invoke it as PID 1, instead of a shell or a user
|
||
supplied program. If this option is used, arguments specified on the command line are used as arguments for the
|
||
init program. This option may not be combined with <option>--as-pid2</option>.</para>
|
||
|
||
<para>The following table explains the different modes of invocation and relationship to
|
||
<option>--as-pid2</option> (see above):</para>
|
||
|
||
<table>
|
||
<title>Invocation Mode</title>
|
||
<tgroup cols='2' align='left' colsep='1' rowsep='1'>
|
||
<colspec colname="switch" />
|
||
<colspec colname="explanation" />
|
||
<thead>
|
||
<row>
|
||
<entry>Switch</entry>
|
||
<entry>Explanation</entry>
|
||
</row>
|
||
</thead>
|
||
<tbody>
|
||
<row>
|
||
<entry>Neither <option>--as-pid2</option> nor <option>--boot</option> specified</entry>
|
||
<entry>The passed parameters are interpreted as the command line, which is executed as PID 1 in the container.</entry>
|
||
</row>
|
||
|
||
<row>
|
||
<entry><option>--as-pid2</option> specified</entry>
|
||
<entry>The passed parameters are interpreted as the command line, which is executed as PID 2 in the container. A stub init process is run as PID 1.</entry>
|
||
</row>
|
||
|
||
<row>
|
||
<entry><option>--boot</option> specified</entry>
|
||
<entry>An init program is automatically searched for and run as PID 1 in the container. The passed parameters are used as invocation parameters for this process.</entry>
|
||
</row>
|
||
|
||
</tbody>
|
||
</tgroup>
|
||
</table>
|
||
|
||
<para>Note that <option>--boot</option> is the default mode of operation if the
|
||
<filename>systemd-nspawn@.service</filename> template unit file is used.</para>
|
||
</listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><option>--chdir=</option></term>
|
||
|
||
<listitem><para>Change to the specified working directory before invoking the process in the container. Expects
|
||
an absolute path in the container's file system namespace.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><option>-E <replaceable>NAME</replaceable>=<replaceable>VALUE</replaceable></option></term>
|
||
<term><option>--setenv=<replaceable>NAME</replaceable>=<replaceable>VALUE</replaceable></option></term>
|
||
|
||
<listitem><para>Specifies an environment variable assignment
|
||
to pass to the init process in the container, in the format
|
||
<literal>NAME=VALUE</literal>. This may be used to override
|
||
the default variables or to set additional variables. This
|
||
parameter may be used more than once.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><option>-u</option></term>
|
||
<term><option>--user=</option></term>
|
||
|
||
<listitem><para>After transitioning into the container, change to the specified user defined in the
|
||
container's user database. Like all other systemd-nspawn features, this is not a security feature and
|
||
provides protection against accidental destructive operations only.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><option>--kill-signal=</option></term>
|
||
|
||
<listitem><para>Specify the process signal to send to the container's PID 1 when nspawn itself receives
|
||
<constant>SIGTERM</constant>, in order to trigger an orderly shutdown of the container. Defaults to
|
||
<constant>SIGRTMIN+3</constant> if <option>--boot</option> is used (on systemd-compatible init systems
|
||
<constant>SIGRTMIN+3</constant> triggers an orderly shutdown). If <option>--boot</option> is not used and this
|
||
option is not specified the container's processes are terminated abruptly via <constant>SIGKILL</constant>. For
|
||
a list of valid signals, see <citerefentry
|
||
project='man-pages'><refentrytitle>signal</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><option>--notify-ready=</option></term>
|
||
|
||
<listitem><para>Configures support for notifications from the container's init process.
|
||
<option>--notify-ready=</option> takes a boolean (<option>no</option> and <option>yes</option>).
|
||
With option <option>no</option> systemd-nspawn notifies systemd
|
||
with a <literal>READY=1</literal> message when the init process is created.
|
||
With option <option>yes</option> systemd-nspawn waits for the
|
||
<literal>READY=1</literal> message from the init process in the container
|
||
before sending its own to systemd. For more details about notifications
|
||
see <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para></listitem>
|
||
</varlistentry>
|
||
</variablelist>
|
||
|
||
</refsect2><refsect2>
|
||
<title>System Identity Options</title>
|
||
|
||
<variablelist>
|
||
<varlistentry>
|
||
<term><option>-M</option></term>
|
||
<term><option>--machine=</option></term>
|
||
|
||
<listitem><para>Sets the machine name for this container. This
|
||
name may be used to identify this container during its runtime
|
||
(for example in tools like
|
||
<citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
|
||
and similar), and is used to initialize the container's
|
||
hostname (which the container can choose to override,
|
||
however). If not specified, the last component of the root
|
||
directory path of the container is used, possibly suffixed
|
||
with a random identifier in case <option>--ephemeral</option>
|
||
mode is selected. If the root directory selected is the host's
|
||
root directory the host's hostname is used as default
|
||
instead.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><option>--hostname=</option></term>
|
||
|
||
<listitem><para>Controls the hostname to set within the container, if different from the machine name. Expects
|
||
a valid hostname as argument. If this option is used, the kernel hostname of the container will be set to this
|
||
value, otherwise it will be initialized to the machine name as controlled by the <option>--machine=</option>
|
||
option described above. The machine name is used for various aspect of identification of the container from the
|
||
outside, the kernel hostname configurable with this option is useful for the container to identify itself from
|
||
the inside. It is usually a good idea to keep both forms of identification synchronized, in order to avoid
|
||
confusion. It is hence recommended to avoid usage of this option, and use <option>--machine=</option>
|
||
exclusively. Note that regardless whether the container's hostname is initialized from the name set with
|
||
<option>--hostname=</option> or the one set with <option>--machine=</option>, the container can later override
|
||
its kernel hostname freely on its own as well.</para>
|
||
</listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><option>--uuid=</option></term>
|
||
|
||
<listitem><para>Set the specified UUID for the container. The
|
||
init system will initialize
|
||
<filename>/etc/machine-id</filename> from this if this file is
|
||
not set yet. Note that this option takes effect only if
|
||
<filename>/etc/machine-id</filename> in the container is
|
||
unpopulated.</para></listitem>
|
||
</varlistentry>
|
||
</variablelist>
|
||
|
||
</refsect2><refsect2>
|
||
<title>Property Options</title>
|
||
|
||
<variablelist>
|
||
<varlistentry>
|
||
<term><option>-S</option></term>
|
||
<term><option>--slice=</option></term>
|
||
|
||
<listitem><para>Make the container part of the specified slice, instead of the default
|
||
<filename>machine.slice</filename>. This applies only if the machine is run in its own scope unit, i.e. if
|
||
<option>--keep-unit</option> isn't used.</para>
|
||
</listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><option>--property=</option></term>
|
||
|
||
<listitem><para>Set a unit property on the scope unit to register for the machine. This applies only if the
|
||
machine is run in its own scope unit, i.e. if <option>--keep-unit</option> isn't used. Takes unit property
|
||
assignments in the same format as <command>systemctl set-property</command>. This is useful to set memory
|
||
limits and similar for container.</para>
|
||
</listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><option>--register=</option></term>
|
||
|
||
<listitem><para>Controls whether the container is registered with
|
||
<citerefentry><refentrytitle>systemd-machined</refentrytitle><manvolnum>8</manvolnum></citerefentry>. Takes a
|
||
boolean argument, which defaults to <literal>yes</literal>. This option should be enabled when the container
|
||
runs a full Operating System (more specifically: a system and service manager as PID 1), and is useful to
|
||
ensure that the container is accessible via
|
||
<citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry> and shown by
|
||
tools such as <citerefentry
|
||
project='man-pages'><refentrytitle>ps</refentrytitle><manvolnum>1</manvolnum></citerefentry>. If the container
|
||
does not run a service manager, it is recommended to set this option to
|
||
<literal>no</literal>.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><option>--keep-unit</option></term>
|
||
|
||
<listitem><para>Instead of creating a transient scope unit to run the container in, simply use the service or
|
||
scope unit <command>systemd-nspawn</command> has been invoked in. If <option>--register=yes</option> is set
|
||
this unit is registered with
|
||
<citerefentry><refentrytitle>systemd-machined</refentrytitle><manvolnum>8</manvolnum></citerefentry>. This
|
||
switch should be used if <command>systemd-nspawn</command> is invoked from within a service unit, and the
|
||
service unit's sole purpose is to run a single <command>systemd-nspawn</command> container. This option is not
|
||
available if run from a user session.</para>
|
||
<para>Note that passing <option>--keep-unit</option> disables the effect of <option>--slice=</option> and
|
||
<option>--property=</option>. Use <option>--keep-unit</option> and <option>--register=no</option> in
|
||
combination to disable any kind of unit allocation or registration with
|
||
<command>systemd-machined</command>.</para></listitem>
|
||
</varlistentry>
|
||
</variablelist>
|
||
|
||
</refsect2><refsect2>
|
||
<title>User Namespacing Options</title>
|
||
|
||
<variablelist>
|
||
<varlistentry>
|
||
<term><option>--private-users=</option></term>
|
||
|
||
<listitem><para>Controls user namespacing. If enabled, the container will run with its own private set of UNIX
|
||
user and group ids (UIDs and GIDs). This involves mapping the private UIDs/GIDs used in the container (starting
|
||
with the container's root user 0 and up) to a range of UIDs/GIDs on the host that are not used for other
|
||
purposes (usually in the range beyond the host's UID/GID 65536). The parameter may be specified as follows:</para>
|
||
|
||
<orderedlist>
|
||
<listitem><para>If one or two colon-separated numbers are specified, user namespacing is turned on. The first
|
||
parameter specifies the first host UID/GID to assign to the container, the second parameter specifies the
|
||
number of host UIDs/GIDs to assign to the container. If the second parameter is omitted, 65536 UIDs/GIDs are
|
||
assigned.</para></listitem>
|
||
|
||
<listitem><para>If the parameter is omitted, or true, user namespacing is turned on. The UID/GID range to
|
||
use is determined automatically from the file ownership of the root directory of the container's directory
|
||
tree. To use this option, make sure to prepare the directory tree in advance, and ensure that all files and
|
||
directories in it are owned by UIDs/GIDs in the range you'd like to use. Also, make sure that used file ACLs
|
||
exclusively reference UIDs/GIDs in the appropriate range. If this mode is used the number of UIDs/GIDs
|
||
assigned to the container for use is 65536, and the UID/GID of the root directory must be a multiple of
|
||
65536.</para></listitem>
|
||
|
||
<listitem><para>If the parameter is false, user namespacing is turned off. This is the default.</para>
|
||
</listitem>
|
||
|
||
<listitem><para>The special value <literal>pick</literal> turns on user namespacing. In this case the UID/GID
|
||
range is automatically chosen. As first step, the file owner of the root directory of the container's
|
||
directory tree is read, and it is checked that it is currently not used by the system otherwise (in
|
||
particular, that no other container is using it). If this check is successful, the UID/GID range determined
|
||
this way is used, similar to the behavior if "yes" is specified. If the check is not successful (and thus
|
||
the UID/GID range indicated in the root directory's file owner is already used elsewhere) a new – currently
|
||
unused – UID/GID range of 65536 UIDs/GIDs is randomly chosen between the host UID/GIDs of 524288 and
|
||
1878982656, always starting at a multiple of 65536. This setting implies
|
||
<option>--private-users-chown</option> (see below), which has the effect that the files and directories in
|
||
the container's directory tree will be owned by the appropriate users of the range picked. Using this option
|
||
makes user namespace behavior fully automatic. Note that the first invocation of a previously unused
|
||
container image might result in picking a new UID/GID range for it, and thus in the (possibly expensive) file
|
||
ownership adjustment operation. However, subsequent invocations of the container will be cheap (unless of
|
||
course the picked UID/GID range is assigned to a different use by then).</para></listitem>
|
||
</orderedlist>
|
||
|
||
<para>It is recommended to assign at least 65536 UIDs/GIDs to each container, so that the usable UID/GID range in the
|
||
container covers 16 bit. For best security, do not assign overlapping UID/GID ranges to multiple containers. It is
|
||
hence a good idea to use the upper 16 bit of the host 32-bit UIDs/GIDs as container identifier, while the lower 16
|
||
bit encode the container UID/GID used. This is in fact the behavior enforced by the
|
||
<option>--private-users=pick</option> option.</para>
|
||
|
||
<para>When user namespaces are used, the GID range assigned to each container is always chosen identical to the
|
||
UID range.</para>
|
||
|
||
<para>In most cases, using <option>--private-users=pick</option> is the recommended option as it enhances
|
||
container security massively and operates fully automatically in most cases.</para>
|
||
|
||
<para>Note that the picked UID/GID range is not written to <filename>/etc/passwd</filename> or
|
||
<filename>/etc/group</filename>. In fact, the allocation of the range is not stored persistently anywhere,
|
||
except in the file ownership of the files and directories of the container.</para>
|
||
|
||
<para>Note that when user namespacing is used file ownership on disk reflects this, and all of the container's
|
||
files and directories are owned by the container's effective user and group IDs. This means that copying files
|
||
from and to the container image requires correction of the numeric UID/GID values, according to the UID/GID
|
||
shift applied.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><option>--private-users-chown</option></term>
|
||
|
||
<listitem><para>If specified, all files and directories in the container's directory tree will be
|
||
adjusted so that they are owned by the appropriate UIDs/GIDs selected for the container (see above).
|
||
This operation is potentially expensive, as it involves iterating through the full directory tree of
|
||
the container. Besides actual file ownership, file ACLs are adjusted as well.</para>
|
||
|
||
<para>This option is implied if <option>--private-users=pick</option> is used. This option has no effect if
|
||
user namespacing is not used.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><option>-U</option></term>
|
||
|
||
<listitem><para>If the kernel supports the user namespaces feature, equivalent to
|
||
<option>--private-users=pick --private-users-chown</option>, otherwise equivalent to
|
||
<option>--private-users=no</option>.</para>
|
||
|
||
<para>Note that <option>-U</option> is the default if the
|
||
<filename>systemd-nspawn@.service</filename> template unit file is used.</para>
|
||
|
||
<para>Note: it is possible to undo the effect of <option>--private-users-chown</option> (or
|
||
<option>-U</option>) on the file system by redoing the operation with the first UID of 0:</para>
|
||
|
||
<programlisting>systemd-nspawn … --private-users=0 --private-users-chown</programlisting>
|
||
</listitem>
|
||
</varlistentry>
|
||
|
||
</variablelist>
|
||
|
||
</refsect2><refsect2>
|
||
<title>Networking Options</title>
|
||
|
||
<variablelist>
|
||
|
||
<varlistentry>
|
||
<term><option>--private-network</option></term>
|
||
|
||
<listitem><para>Disconnect networking of the container from
|
||
the host. This makes all network interfaces unavailable in the
|
||
container, with the exception of the loopback device and those
|
||
specified with <option>--network-interface=</option> and
|
||
configured with <option>--network-veth</option>. If this
|
||
option is specified, the <constant>CAP_NET_ADMIN</constant> capability will be
|
||
added to the set of capabilities the container retains. The
|
||
latter may be disabled by using <option>--drop-capability=</option>.
|
||
If this option is not specified (or implied by one of the options
|
||
listed below), the container will have full access to the host network.
|
||
</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><option>--network-interface=</option></term>
|
||
|
||
<listitem><para>Assign the specified network interface to the
|
||
container. This will remove the specified interface from the
|
||
calling namespace and place it in the container. When the
|
||
container terminates, it is moved back to the host namespace.
|
||
Note that <option>--network-interface=</option> implies
|
||
<option>--private-network</option>. This option may be used
|
||
more than once to add multiple network interfaces to the
|
||
container.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><option>--network-macvlan=</option></term>
|
||
|
||
<listitem><para>Create a <literal>macvlan</literal> interface
|
||
of the specified Ethernet network interface and add it to the
|
||
container. A <literal>macvlan</literal> interface is a virtual
|
||
interface that adds a second MAC address to an existing
|
||
physical Ethernet link. The interface in the container will be
|
||
named after the interface on the host, prefixed with
|
||
<literal>mv-</literal>. Note that
|
||
<option>--network-macvlan=</option> implies
|
||
<option>--private-network</option>. This option may be used
|
||
more than once to add multiple network interfaces to the
|
||
container.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><option>--network-ipvlan=</option></term>
|
||
|
||
<listitem><para>Create an <literal>ipvlan</literal> interface
|
||
of the specified Ethernet network interface and add it to the
|
||
container. An <literal>ipvlan</literal> interface is a virtual
|
||
interface, similar to a <literal>macvlan</literal> interface,
|
||
which uses the same MAC address as the underlying interface.
|
||
The interface in the container will be named after the
|
||
interface on the host, prefixed with <literal>iv-</literal>.
|
||
Note that <option>--network-ipvlan=</option> implies
|
||
<option>--private-network</option>. This option may be used
|
||
more than once to add multiple network interfaces to the
|
||
container.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><option>-n</option></term>
|
||
<term><option>--network-veth</option></term>
|
||
|
||
<listitem><para>Create a virtual Ethernet link (<literal>veth</literal>) between host and container. The host
|
||
side of the Ethernet link will be available as a network interface named after the container's name (as
|
||
specified with <option>--machine=</option>), prefixed with <literal>ve-</literal>. The container side of the
|
||
Ethernet link will be named <literal>host0</literal>. The <option>--network-veth</option> option implies
|
||
<option>--private-network</option>.</para>
|
||
|
||
<para>Note that
|
||
<citerefentry><refentrytitle>systemd-networkd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
|
||
includes by default a network file <filename>/usr/lib/systemd/network/80-container-ve.network</filename>
|
||
matching the host-side interfaces created this way, which contains settings to enable automatic address
|
||
provisioning on the created virtual link via DHCP, as well as automatic IP routing onto the host's external
|
||
network interfaces. It also contains <filename>/usr/lib/systemd/network/80-container-host0.network</filename>
|
||
matching the container-side interface created this way, containing settings to enable client side address
|
||
assignment via DHCP. In case <filename>systemd-networkd</filename> is running on both the host and inside the
|
||
container, automatic IP communication from the container to the host is thus available, with further
|
||
connectivity to the external network.</para>
|
||
|
||
<para>Note that <option>--network-veth</option> is the default if the
|
||
<filename>systemd-nspawn@.service</filename> template unit file is used.</para>
|
||
|
||
<para>Note that on Linux network interface names may have a length of 15 characters at maximum, while
|
||
container names may have a length up to 64 characters. As this option derives the host-side interface
|
||
name from the container name the name is possibly truncated. Thus, care needs to be taken to ensure
|
||
that interface names remain unique in this case, or even better container names are generally not
|
||
chosen longer than 12 characters, to avoid the truncation. If the name is truncated,
|
||
<command>systemd-nspawn</command> will automatically append a 4-digit hash value to the name to
|
||
reduce the chance of collisions. However, the hash algorithm is not collision-free. (See
|
||
<citerefentry><refentrytitle>systemd.net-naming-scheme</refentrytitle><manvolnum>7</manvolnum></citerefentry>
|
||
for details on older naming algorithms for this interface). Alternatively, the
|
||
<option>--network-veth-extra=</option> option may be used, which allows free configuration of the
|
||
host-side interface name independently of the container name — but might require a bit more
|
||
additional configuration in case bridging in a fashion similar to <option>--network-bridge=</option>
|
||
is desired.</para>
|
||
</listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><option>--network-veth-extra=</option></term>
|
||
|
||
<listitem><para>Adds an additional virtual Ethernet link
|
||
between host and container. Takes a colon-separated pair of
|
||
host interface name and container interface name. The latter
|
||
may be omitted in which case the container and host sides will
|
||
be assigned the same name. This switch is independent of
|
||
<option>--network-veth</option>, and — in contrast — may be
|
||
used multiple times, and allows configuration of the network
|
||
interface names. Note that <option>--network-bridge=</option>
|
||
has no effect on interfaces created with
|
||
<option>--network-veth-extra=</option>.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><option>--network-bridge=</option></term>
|
||
|
||
<listitem><para>Adds the host side of the Ethernet link created with <option>--network-veth</option>
|
||
to the specified Ethernet bridge interface. Expects a valid network interface name of a bridge device
|
||
as argument. Note that <option>--network-bridge=</option> implies <option>--network-veth</option>. If
|
||
this option is used, the host side of the Ethernet link will use the <literal>vb-</literal> prefix
|
||
instead of <literal>ve-</literal>. Regardless of the used naming prefix the same network interface
|
||
name length limits imposed by Linux apply, along with the complications this creates (for details see
|
||
above).</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><option>--network-zone=</option></term>
|
||
|
||
<listitem><para>Creates a virtual Ethernet link (<literal>veth</literal>) to the container and adds it to an
|
||
automatically managed Ethernet bridge interface. The bridge interface is named after the passed argument,
|
||
prefixed with <literal>vz-</literal>. The bridge interface is automatically created when the first container
|
||
configured for its name is started, and is automatically removed when the last container configured for its
|
||
name exits. Hence, each bridge interface configured this way exists only as long as there's at least one
|
||
container referencing it running. This option is very similar to <option>--network-bridge=</option>, besides
|
||
this automatic creation/removal of the bridge device.</para>
|
||
|
||
<para>This setting makes it easy to place multiple related containers on a common, virtual Ethernet-based
|
||
broadcast domain, here called a "zone". Each container may only be part of one zone, but each zone may contain
|
||
any number of containers. Each zone is referenced by its name. Names may be chosen freely (as long as they form
|
||
valid network interface names when prefixed with <literal>vz-</literal>), and it is sufficient to pass the same
|
||
name to the <option>--network-zone=</option> switch of the various concurrently running containers to join
|
||
them in one zone.</para>
|
||
|
||
<para>Note that
|
||
<citerefentry><refentrytitle>systemd-networkd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
|
||
includes by default a network file <filename>/usr/lib/systemd/network/80-container-vz.network</filename>
|
||
matching the bridge interfaces created this way, which contains settings to enable automatic address
|
||
provisioning on the created virtual network via DHCP, as well as automatic IP routing onto the host's external
|
||
network interfaces. Using <option>--network-zone=</option> is hence in most cases fully automatic and
|
||
sufficient to connect multiple local containers in a joined broadcast domain to the host, with further
|
||
connectivity to the external network.</para>
|
||
</listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><option>--network-namespace-path=</option></term>
|
||
|
||
<listitem><para>Takes the path to a file representing a kernel
|
||
network namespace that the container shall run in. The specified path
|
||
should refer to a (possibly bind-mounted) network namespace file, as
|
||
exposed by the kernel below <filename>/proc/$PID/ns/net</filename>.
|
||
This makes the container enter the given network namespace. One of the
|
||
typical use cases is to give a network namespace under
|
||
<filename>/run/netns</filename> created by <citerefentry
|
||
project='man-pages'><refentrytitle>ip-netns</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
|
||
for example, <option>--network-namespace-path=/run/netns/foo</option>.
|
||
Note that this option cannot be used together with other
|
||
network-related options, such as <option>--private-network</option>
|
||
or <option>--network-interface=</option>.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><option>-p</option></term>
|
||
<term><option>--port=</option></term>
|
||
|
||
<listitem><para>If private networking is enabled, maps an IP
|
||
port on the host onto an IP port on the container. Takes a
|
||
protocol specifier (either <literal>tcp</literal> or
|
||
<literal>udp</literal>), separated by a colon from a host port
|
||
number in the range 1 to 65535, separated by a colon from a
|
||
container port number in the range from 1 to 65535. The
|
||
protocol specifier and its separating colon may be omitted, in
|
||
which case <literal>tcp</literal> is assumed. The container
|
||
port number and its colon may be omitted, in which case the
|
||
same port as the host port is implied. This option is only
|
||
supported if private networking is used, such as with
|
||
<option>--network-veth</option>, <option>--network-zone=</option>
|
||
<option>--network-bridge=</option>.</para></listitem>
|
||
</varlistentry>
|
||
</variablelist>
|
||
|
||
</refsect2><refsect2>
|
||
<title>Security Options</title>
|
||
|
||
<variablelist>
|
||
<varlistentry>
|
||
<term><option>--capability=</option></term>
|
||
|
||
<listitem><para>List one or more additional capabilities to grant the container. Takes a
|
||
comma-separated list of capability names, see <citerefentry
|
||
project='man-pages'><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
|
||
for more information. Note that the following capabilities will be granted in any way:
|
||
<constant>CAP_AUDIT_CONTROL</constant>, <constant>CAP_AUDIT_WRITE</constant>,
|
||
<constant>CAP_CHOWN</constant>, <constant>CAP_DAC_OVERRIDE</constant>,
|
||
<constant>CAP_DAC_READ_SEARCH</constant>, <constant>CAP_FOWNER</constant>,
|
||
<constant>CAP_FSETID</constant>, <constant>CAP_IPC_OWNER</constant>, <constant>CAP_KILL</constant>,
|
||
<constant>CAP_LEASE</constant>, <constant>CAP_LINUX_IMMUTABLE</constant>,
|
||
<constant>CAP_MKNOD</constant>, <constant>CAP_NET_BIND_SERVICE</constant>,
|
||
<constant>CAP_NET_BROADCAST</constant>, <constant>CAP_NET_RAW</constant>,
|
||
<constant>CAP_SETFCAP</constant>, <constant>CAP_SETGID</constant>, <constant>CAP_SETPCAP</constant>,
|
||
<constant>CAP_SETUID</constant>, <constant>CAP_SYS_ADMIN</constant>,
|
||
<constant>CAP_SYS_BOOT</constant>, <constant>CAP_SYS_CHROOT</constant>,
|
||
<constant>CAP_SYS_NICE</constant>, <constant>CAP_SYS_PTRACE</constant>,
|
||
<constant>CAP_SYS_RESOURCE</constant>, <constant>CAP_SYS_TTY_CONFIG</constant>. Also
|
||
<constant>CAP_NET_ADMIN</constant> is retained if <option>--private-network</option> is specified.
|
||
If the special value <literal>all</literal> is passed, all capabilities are retained.</para>
|
||
|
||
<para>If the special value of <literal>help</literal> is passed, the program will print known
|
||
capability names and exit.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><option>--drop-capability=</option></term>
|
||
|
||
<listitem><para>Specify one or more additional capabilities to
|
||
drop for the container. This allows running the container with
|
||
fewer capabilities than the default (see
|
||
above).</para>
|
||
|
||
<para>If the special value of <literal>help</literal> is passed, the program will print known
|
||
capability names and exit.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><option>--no-new-privileges=</option></term>
|
||
|
||
<listitem><para>Takes a boolean argument. Specifies the value of the
|
||
<constant>PR_SET_NO_NEW_PRIVS</constant> flag for the container payload. Defaults to off. When turned
|
||
on the payload code of the container cannot acquire new privileges, i.e. the "setuid" file bit as
|
||
well as file system capabilities will not have an effect anymore. See <citerefentry
|
||
project='man-pages'><refentrytitle>prctl</refentrytitle><manvolnum>2</manvolnum></citerefentry> for
|
||
details about this flag. </para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><option>--system-call-filter=</option></term> <listitem><para>Alter the system call filter
|
||
applied to containers. Takes a space-separated list of system call names or group names (the latter
|
||
prefixed with <literal>@</literal>, as listed by the <command>syscall-filter</command> command of
|
||
<citerefentry><refentrytitle>systemd-analyze</refentrytitle><manvolnum>1</manvolnum></citerefentry>). Passed
|
||
system calls will be permitted. The list may optionally be prefixed by <literal>~</literal>, in which
|
||
case all listed system calls are prohibited. If this command line option is used multiple times the
|
||
configured lists are combined. If both a positive and a negative list (that is one system call list
|
||
without and one with the <literal>~</literal> prefix) are configured, the negative list takes
|
||
precedence over the positive list. Note that <command>systemd-nspawn</command> always implements a
|
||
system call allow list (as opposed to a deny list!), and this command line option hence adds or
|
||
removes entries from the default allow list, depending on the <literal>~</literal> prefix. Note that
|
||
the applied system call filter is also altered implicitly if additional capabilities are passed using
|
||
the <command>--capabilities=</command>.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><option>-Z</option></term>
|
||
<term><option>--selinux-context=</option></term>
|
||
|
||
<listitem><para>Sets the SELinux security context to be used
|
||
to label processes in the container.</para>
|
||
</listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><option>-L</option></term>
|
||
<term><option>--selinux-apifs-context=</option></term>
|
||
|
||
<listitem><para>Sets the SELinux security context to be used
|
||
to label files in the virtual API file systems in the
|
||
container.</para>
|
||
</listitem>
|
||
</varlistentry>
|
||
</variablelist>
|
||
|
||
</refsect2><refsect2>
|
||
<title>Resource Options</title>
|
||
|
||
<variablelist>
|
||
|
||
<varlistentry>
|
||
<term><option>--rlimit=</option></term>
|
||
|
||
<listitem><para>Sets the specified POSIX resource limit for the container payload. Expects an assignment of the
|
||
form
|
||
<literal><replaceable>LIMIT</replaceable>=<replaceable>SOFT</replaceable>:<replaceable>HARD</replaceable></literal>
|
||
or <literal><replaceable>LIMIT</replaceable>=<replaceable>VALUE</replaceable></literal>, where
|
||
<replaceable>LIMIT</replaceable> should refer to a resource limit type, such as
|
||
<constant>RLIMIT_NOFILE</constant> or <constant>RLIMIT_NICE</constant>. The <replaceable>SOFT</replaceable> and
|
||
<replaceable>HARD</replaceable> fields should refer to the numeric soft and hard resource limit values. If the
|
||
second form is used, <replaceable>VALUE</replaceable> may specify a value that is used both as soft and hard
|
||
limit. In place of a numeric value the special string <literal>infinity</literal> may be used to turn off
|
||
resource limiting for the specific type of resource. This command line option may be used multiple times to
|
||
control limits on multiple limit types. If used multiple times for the same limit type, the last use
|
||
wins. For details about resource limits see <citerefentry
|
||
project='man-pages'><refentrytitle>setrlimit</refentrytitle><manvolnum>2</manvolnum></citerefentry>. By default
|
||
resource limits for the container's init process (PID 1) are set to the same values the Linux kernel originally
|
||
passed to the host init system. Note that some resource limits are enforced on resources counted per user, in
|
||
particular <constant>RLIMIT_NPROC</constant>. This means that unless user namespacing is deployed
|
||
(i.e. <option>--private-users=</option> is used, see above), any limits set will be applied to the resource
|
||
usage of the same user on all local containers as well as the host. This means particular care needs to be
|
||
taken with these limits as they might be triggered by possibly less trusted code. Example:
|
||
<literal>--rlimit=RLIMIT_NOFILE=8192:16384</literal>.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><option>--oom-score-adjust=</option></term>
|
||
|
||
<listitem><para>Changes the OOM ("Out Of Memory") score adjustment value for the container payload. This controls
|
||
<filename>/proc/self/oom_score_adj</filename> which influences the preference with which this container is
|
||
terminated when memory becomes scarce. For details see <citerefentry
|
||
project='man-pages'><refentrytitle>proc</refentrytitle><manvolnum>5</manvolnum></citerefentry>. Takes an
|
||
integer in the range -1000…1000.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><option>--cpu-affinity=</option></term>
|
||
|
||
<listitem><para>Controls the CPU affinity of the container payload. Takes a comma separated list of CPU numbers
|
||
or number ranges (the latter's start and end value separated by dashes). See <citerefentry
|
||
project='man-pages'><refentrytitle>sched_setaffinity</refentrytitle><manvolnum>2</manvolnum></citerefentry> for
|
||
details.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><option>--personality=</option></term>
|
||
|
||
<listitem><para>Control the architecture ("personality")
|
||
reported by
|
||
<citerefentry project='man-pages'><refentrytitle>uname</refentrytitle><manvolnum>2</manvolnum></citerefentry>
|
||
in the container. Currently, only <literal>x86</literal> and
|
||
<literal>x86-64</literal> are supported. This is useful when
|
||
running a 32-bit container on a 64-bit host. If this setting
|
||
is not used, the personality reported in the container is the
|
||
same as the one reported on the host.</para></listitem>
|
||
</varlistentry>
|
||
</variablelist>
|
||
|
||
</refsect2><refsect2>
|
||
<title>Integration Options</title>
|
||
|
||
<variablelist>
|
||
<varlistentry>
|
||
<term><option>--resolv-conf=</option></term>
|
||
|
||
<listitem><para>Configures how <filename>/etc/resolv.conf</filename> inside of the container shall be
|
||
handled (i.e. DNS configuration synchronization from host to container). Takes one of
|
||
<literal>off</literal>, <literal>copy-host</literal>, <literal>copy-static</literal>,
|
||
<literal>copy-uplink</literal>, <literal>copy-stub</literal>, <literal>replace-host</literal>,
|
||
<literal>replace-static</literal>, <literal>replace-uplink</literal>,
|
||
<literal>replace-stub</literal>, <literal>bind-host</literal>, <literal>bind-static</literal>,
|
||
<literal>bind-uplink</literal>, <literal>bind-stub</literal>, <literal>delete</literal> or
|
||
<literal>auto</literal>.</para>
|
||
|
||
<para>If set to <literal>off</literal> the <filename>/etc/resolv.conf</filename> file in the
|
||
container is left as it is included in the image, and neither modified nor bind mounted over.</para>
|
||
|
||
<para>If set to <literal>copy-host</literal>, the <filename>/etc/resolv.conf</filename> file from the
|
||
host is copied into the container, unless the file exists already and is not a regular file (e.g. a
|
||
symlink). Similar, if <literal>replace-host</literal> is used the file is copied, replacing any
|
||
existing inode, including symlinks. Similar, if <literal>bind-host</literal> is used, the file is
|
||
bind mounted from the host into the container.</para>
|
||
|
||
<para>If set to <literal>copy-static</literal>, <literal>replace-static</literal> or
|
||
<literal>bind-static</literal> the static <filename>resolv.conf</filename> file supplied with
|
||
<citerefentry><refentrytitle>systemd-resolved.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
|
||
(specifically: <filename>/usr/lib/systemd/resolv.conf</filename>) is copied or bind mounted into the
|
||
container.</para>
|
||
|
||
<para>If set to <literal>copy-uplink</literal>, <literal>replace-uplink</literal> or
|
||
<literal>bind-uplink</literal> the uplink <filename>resolv.conf</filename> file managed by
|
||
<filename>systemd-resolved.service</filename> (specifically:
|
||
<filename>/run/systemd/resolve/resolv.conf</filename>) is copied or bind mounted into the
|
||
container.</para>
|
||
|
||
<para>If set to <literal>copy-stub</literal>, <literal>replace-stub</literal> or
|
||
<literal>bind-stub</literal> the stub <filename>resolv.conf</filename> file managed by
|
||
<filename>systemd-resolved.service</filename> (specifically:
|
||
<filename>/run/systemd/resolve/stub-resolv.conf</filename>) is copied or bind mounted into the
|
||
container.</para>
|
||
|
||
<para>If set to <literal>delete</literal> the <filename>/etc/resolv.conf</filename> file in the
|
||
container is deleted if it exists.</para>
|
||
|
||
<para>Finally, if set to <literal>auto</literal> the file is left as it is if private networking is
|
||
turned on (see <option>--private-network</option>). Otherwise, if
|
||
<filename>systemd-resolved.service</filename> is running its stub <filename>resolv.conf</filename>
|
||
file is used, and if not the host's <filename>/etc/resolv.conf</filename> file. In the latter cases
|
||
the file is copied if the image is writable, and bind mounted otherwise.</para>
|
||
|
||
<para>It's recommended to use <literal>copy-…</literal> or <literal>replace-…</literal> if the
|
||
container shall be able to make changes to the DNS configuration on its own, deviating from the
|
||
host's settings. Otherwise <literal>bind</literal> is preferable, as it means direct changes to
|
||
<filename>/etc/resolv.conf</filename> in the container are not allowed, as it is a read-only bind
|
||
mount (but note that if the container has enough privileges, it might simply go ahead and unmount the
|
||
bind mount anyway). Note that both if the file is bind mounted and if it is copied no further
|
||
propagation of configuration is generally done after the one-time early initialization (this is
|
||
because the file is usually updated through copying and renaming). Defaults to
|
||
<literal>auto</literal>.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><option>--timezone=</option></term>
|
||
|
||
<listitem><para>Configures how <filename>/etc/localtime</filename> inside of the container
|
||
(i.e. local timezone synchronization from host to container) shall be handled. Takes one of
|
||
<literal>off</literal>, <literal>copy</literal>, <literal>bind</literal>, <literal>symlink</literal>,
|
||
<literal>delete</literal> or <literal>auto</literal>. If set to <literal>off</literal> the
|
||
<filename>/etc/localtime</filename> file in the container is left as it is included in the image, and
|
||
neither modified nor bind mounted over. If set to <literal>copy</literal> the
|
||
<filename>/etc/localtime</filename> file of the host is copied into the container. Similarly, if
|
||
<literal>bind</literal> is used, the file is bind mounted from the host into the container. If set to
|
||
<literal>symlink</literal>, a symlink is created pointing from <filename>/etc/localtime</filename> in
|
||
the container to the timezone file in the container that matches the timezone setting on the host. If
|
||
set to <literal>delete</literal>, the file in the container is deleted, should it exist. If set to
|
||
<literal>auto</literal> and the <filename>/etc/localtime</filename> file of the host is a symlink,
|
||
then <literal>symlink</literal> mode is used, and <literal>copy</literal> otherwise, except if the
|
||
image is read-only in which case <literal>bind</literal> is used instead. Defaults to
|
||
<literal>auto</literal>.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><option>--link-journal=</option></term>
|
||
|
||
<listitem><para>Control whether the container's journal shall
|
||
be made visible to the host system. If enabled, allows viewing
|
||
the container's journal files from the host (but not vice
|
||
versa). Takes one of <literal>no</literal>,
|
||
<literal>host</literal>, <literal>try-host</literal>,
|
||
<literal>guest</literal>, <literal>try-guest</literal>,
|
||
<literal>auto</literal>. If <literal>no</literal>, the journal
|
||
is not linked. If <literal>host</literal>, the journal files
|
||
are stored on the host file system (beneath
|
||
<filename>/var/log/journal/<replaceable>machine-id</replaceable></filename>)
|
||
and the subdirectory is bind-mounted into the container at the
|
||
same location. If <literal>guest</literal>, the journal files
|
||
are stored on the guest file system (beneath
|
||
<filename>/var/log/journal/<replaceable>machine-id</replaceable></filename>)
|
||
and the subdirectory is symlinked into the host at the same
|
||
location. <literal>try-host</literal> and
|
||
<literal>try-guest</literal> do the same but do not fail if
|
||
the host does not have persistent journaling enabled. If
|
||
<literal>auto</literal> (the default), and the right
|
||
subdirectory of <filename>/var/log/journal</filename> exists,
|
||
it will be bind mounted into the container. If the
|
||
subdirectory does not exist, no linking is performed.
|
||
Effectively, booting a container once with
|
||
<literal>guest</literal> or <literal>host</literal> will link
|
||
the journal persistently if further on the default of
|
||
<literal>auto</literal> is used.</para>
|
||
|
||
<para>Note that <option>--link-journal=try-guest</option> is the default if the
|
||
<filename>systemd-nspawn@.service</filename> template unit file is used.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><option>-j</option></term>
|
||
|
||
<listitem><para>Equivalent to
|
||
<option>--link-journal=try-guest</option>.</para></listitem>
|
||
</varlistentry>
|
||
|
||
</variablelist>
|
||
|
||
</refsect2><refsect2>
|
||
<title>Mount Options</title>
|
||
|
||
<variablelist>
|
||
|
||
<varlistentry>
|
||
<term><option>--bind=</option></term>
|
||
<term><option>--bind-ro=</option></term>
|
||
|
||
<listitem><para>Bind mount a file or directory from the host into the container. Takes one of: a path
|
||
argument — in which case the specified path will be mounted from the host to the same path in the container, or
|
||
a colon-separated pair of paths — in which case the first specified path is the source in the host, and the
|
||
second path is the destination in the container, or a colon-separated triple of source path, destination path
|
||
and mount options. The source path may optionally be prefixed with a <literal>+</literal> character. If so, the
|
||
source path is taken relative to the image's root directory. This permits setting up bind mounts within the
|
||
container image. The source path may be specified as empty string, in which case a temporary directory below
|
||
the host's <filename>/var/tmp</filename> directory is used. It is automatically removed when the container is
|
||
shut down. Mount options are comma-separated and currently, only <option>rbind</option> and
|
||
<option>norbind</option> are allowed, controlling whether to create a recursive or a regular bind
|
||
mount. Defaults to "rbind". Backslash escapes are interpreted, so <literal>\:</literal> may be used to embed
|
||
colons in either path. This option may be specified multiple times for creating multiple independent bind
|
||
mount points. The <option>--bind-ro=</option> option creates read-only bind mounts.</para>
|
||
|
||
<para>Note that when this option is used in combination with <option>--private-users</option>, the resulting
|
||
mount points will be owned by the <constant>nobody</constant> user. That's because the mount and its files and
|
||
directories continue to be owned by the relevant host users and groups, which do not exist in the container,
|
||
and thus show up under the wildcard UID 65534 (nobody). If such bind mounts are created, it is recommended to
|
||
make them read-only, using <option>--bind-ro=</option>.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><option>--inaccessible=</option></term>
|
||
|
||
<listitem><para>Make the specified path inaccessible in the container. This over-mounts the specified path
|
||
(which must exist in the container) with a file node of the same type that is empty and has the most
|
||
restrictive access mode supported. This is an effective way to mask files, directories and other file system
|
||
objects from the container payload. This option may be used more than once in case all specified paths are
|
||
masked.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><option>--tmpfs=</option></term>
|
||
|
||
<listitem><para>Mount a tmpfs file system into the container. Takes a single absolute path argument that
|
||
specifies where to mount the tmpfs instance to (in which case the directory access mode will be chosen as 0755,
|
||
owned by root/root), or optionally a colon-separated pair of path and mount option string that is used for
|
||
mounting (in which case the kernel default for access mode and owner will be chosen, unless otherwise
|
||
specified). Backslash escapes are interpreted in the path, so <literal>\:</literal> may be used to embed colons
|
||
in the path.</para>
|
||
|
||
<para>Note that this option cannot be used to replace the root file system of the container with a temporary
|
||
file system. However, the <option>--volatile=</option> option described below provides similar
|
||
functionality, with a focus on implementing stateless operating system images.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><option>--overlay=</option></term>
|
||
<term><option>--overlay-ro=</option></term>
|
||
|
||
<listitem><para>Combine multiple directory trees into one
|
||
overlay file system and mount it into the container. Takes a
|
||
list of colon-separated paths to the directory trees to
|
||
combine and the destination mount point.</para>
|
||
|
||
<para>Backslash escapes are interpreted in the paths, so
|
||
<literal>\:</literal> may be used to embed colons in the paths.
|
||
</para>
|
||
|
||
<para>If three or more paths are specified, then the last
|
||
specified path is the destination mount point in the
|
||
container, all paths specified before refer to directory trees
|
||
on the host and are combined in the specified order into one
|
||
overlay file system. The left-most path is hence the lowest
|
||
directory tree, the second-to-last path the highest directory
|
||
tree in the stacking order. If <option>--overlay-ro=</option>
|
||
is used instead of <option>--overlay=</option>, a read-only
|
||
overlay file system is created. If a writable overlay file
|
||
system is created, all changes made to it are written to the
|
||
highest directory tree in the stacking order, i.e. the
|
||
second-to-last specified.</para>
|
||
|
||
<para>If only two paths are specified, then the second
|
||
specified path is used both as the top-level directory tree in
|
||
the stacking order as seen from the host, as well as the mount
|
||
point for the overlay file system in the container. At least
|
||
two paths have to be specified.</para>
|
||
|
||
<para>The source paths may optionally be prefixed with <literal>+</literal> character. If so they are taken
|
||
relative to the image's root directory. The uppermost source path may also be specified as empty string, in
|
||
which case a temporary directory below the host's <filename>/var/tmp</filename> is used. The directory is
|
||
removed automatically when the container is shut down. This behaviour is useful in order to make read-only
|
||
container directories writable while the container is running. For example, use the
|
||
<literal>--overlay=+/var::/var</literal> option in order to automatically overlay a writable temporary
|
||
directory on a read-only <filename>/var</filename> directory.</para>
|
||
|
||
<para>For details about overlay file systems, see <ulink
|
||
url="https://www.kernel.org/doc/Documentation/filesystems/overlayfs.txt">overlayfs.txt</ulink>. Note
|
||
that the semantics of overlay file systems are substantially
|
||
different from normal file systems, in particular regarding
|
||
reported device and inode information. Device and inode
|
||
information may change for a file while it is being written
|
||
to, and processes might see out-of-date versions of files at
|
||
times. Note that this switch automatically derives the
|
||
<literal>workdir=</literal> mount option for the overlay file
|
||
system from the top-level directory tree, making it a sibling
|
||
of it. It is hence essential that the top-level directory tree
|
||
is not a mount point itself (since the working directory must
|
||
be on the same file system as the top-most directory
|
||
tree). Also note that the <literal>lowerdir=</literal> mount
|
||
option receives the paths to stack in the opposite order of
|
||
this switch.</para>
|
||
|
||
<para>Note that this option cannot be used to replace the root file system of the container with an overlay
|
||
file system. However, the <option>--volatile=</option> option described above provides similar functionality,
|
||
with a focus on implementing stateless operating system images.</para></listitem>
|
||
</varlistentry>
|
||
</variablelist>
|
||
|
||
</refsect2><refsect2>
|
||
<title>Input/Output Options</title>
|
||
|
||
<variablelist>
|
||
<varlistentry>
|
||
<term><option>--console=</option><replaceable>MODE</replaceable></term>
|
||
|
||
<listitem><para>Configures how to set up standard input, output and error output for the container
|
||
payload, as well as the <filename>/dev/console</filename> device for the container. Takes one of
|
||
<option>interactive</option>, <option>read-only</option>, <option>passive</option>, or
|
||
<option>pipe</option>. If <option>interactive</option>, a pseudo-TTY is allocated and made available
|
||
as <filename>/dev/console</filename> in the container. It is then bi-directionally connected to the
|
||
standard input and output passed to <command>systemd-nspawn</command>. <option>read-only</option> is
|
||
similar but only the output of the container is propagated and no input from the caller is read. If
|
||
<option>passive</option>, a pseudo TTY is allocated, but it is not connected anywhere. Finally, in
|
||
<option>pipe</option> mode no pseudo TTY is allocated, but the standard input, output and error
|
||
output file descriptors passed to <command>systemd-nspawn</command> are passed on — as they are — to
|
||
the container payload, see the following paragraph. Defaults to <option>interactive</option> if
|
||
<command>systemd-nspawn</command> is invoked from a terminal, and <option>read-only</option>
|
||
otherwise.</para>
|
||
|
||
<para>In <option>pipe</option> mode, <filename>/dev/console</filename> will not exist in the
|
||
container. This means that the container payload generally cannot be a full init system as init
|
||
systems tend to require <filename>/dev/console</filename> to be available. On the other hand, in this
|
||
mode container invocations can be used within shell pipelines. This is because intermediary pseudo
|
||
TTYs do not permit independent bidirectional propagation of the end-of-file (EOF) condition, which is
|
||
necessary for shell pipelines to work correctly. <emphasis>Note that the <option>pipe</option> mode
|
||
should be used carefully</emphasis>, as passing arbitrary file descriptors to less trusted container
|
||
payloads might open up unwanted interfaces for access by the container payload. For example, if a
|
||
passed file descriptor refers to a TTY of some form, APIs such as <constant>TIOCSTI</constant> may be
|
||
used to synthesize input that might be used for escaping the container. Hence <option>pipe</option>
|
||
mode should only be used if the payload is sufficiently trusted or when the standard
|
||
input/output/error output file descriptors are known safe, for example pipes.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><option>--pipe</option></term>
|
||
<term><option>-P</option></term>
|
||
|
||
<listitem><para>Equivalent to <option>--console=pipe</option>.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<xi:include href="standard-options.xml" xpointer="no-pager" />
|
||
<xi:include href="standard-options.xml" xpointer="help" />
|
||
<xi:include href="standard-options.xml" xpointer="version" />
|
||
</variablelist>
|
||
</refsect2>
|
||
</refsect1>
|
||
|
||
<xi:include href="less-variables.xml" />
|
||
|
||
<refsect1>
|
||
<title>Examples</title>
|
||
|
||
<example>
|
||
<title>Download a
|
||
<ulink url="https://getfedora.org">Fedora</ulink> image and start a shell in it</title>
|
||
|
||
<programlisting># machinectl pull-raw --verify=no \
|
||
https://download.fedoraproject.org/pub/fedora/linux/releases/&fedora_latest_version;/Cloud/x86_64/images/Fedora-Cloud-Base-&fedora_latest_version;-&fedora_cloud_release;.x86_64.raw.xz \
|
||
Fedora-Cloud-Base-&fedora_latest_version;-&fedora_cloud_release;.x86-64
|
||
# systemd-nspawn -M Fedora-Cloud-Base-&fedora_latest_version;-&fedora_cloud_release;.x86-64</programlisting>
|
||
|
||
<para>This downloads an image using
|
||
<citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
|
||
and opens a shell in it.</para>
|
||
</example>
|
||
|
||
<example>
|
||
<title>Build and boot a minimal Fedora distribution in a container</title>
|
||
|
||
<programlisting># dnf -y --releasever=&fedora_latest_version; --installroot=/var/lib/machines/f&fedora_latest_version; \
|
||
--disablerepo='*' --enablerepo=fedora --enablerepo=updates install \
|
||
systemd passwd dnf fedora-release vim-minimal glibc-minimal-langpack
|
||
# systemd-nspawn -bD /var/lib/machines/f&fedora_latest_version;</programlisting>
|
||
|
||
<para>This installs a minimal Fedora distribution into the
|
||
directory <filename index="false">/var/lib/machines/f&fedora_latest_version;</filename>
|
||
and then boots that OS in a namespace container. Because the installation
|
||
is located underneath the standard <filename>/var/lib/machines/</filename>
|
||
directory, it is also possible to start the machine using
|
||
<command>systemd-nspawn -M f&fedora_latest_version;</command>.</para>
|
||
</example>
|
||
|
||
<example>
|
||
<title>Spawn a shell in a container of a minimal Debian unstable distribution</title>
|
||
|
||
<programlisting># debootstrap unstable ~/debian-tree/
|
||
# systemd-nspawn -D ~/debian-tree/</programlisting>
|
||
|
||
<para>This installs a minimal Debian unstable distribution into
|
||
the directory <filename>~/debian-tree/</filename> and then
|
||
spawns a shell from this image in a namespace container.</para>
|
||
|
||
<para><command>debootstrap</command> supports
|
||
<ulink url="https://www.debian.org">Debian</ulink>,
|
||
<ulink url="https://www.ubuntu.com">Ubuntu</ulink>,
|
||
and <ulink url="https://www.tanglu.org">Tanglu</ulink>
|
||
out of the box, so the same command can be used to install any of those. For other
|
||
distributions from the Debian family, a mirror has to be specified, see
|
||
<citerefentry project='die-net'><refentrytitle>debootstrap</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
|
||
</para>
|
||
</example>
|
||
|
||
<example>
|
||
<title>Boot a minimal
|
||
<ulink url="https://www.archlinux.org">Arch Linux</ulink> distribution in a container</title>
|
||
|
||
<programlisting># pacstrap -c ~/arch-tree/ base
|
||
# systemd-nspawn -bD ~/arch-tree/</programlisting>
|
||
|
||
<para>This installs a minimal Arch Linux distribution into the
|
||
directory <filename>~/arch-tree/</filename> and then boots an OS
|
||
in a namespace container in it.</para>
|
||
</example>
|
||
|
||
<example>
|
||
<title>Install the
|
||
<ulink url="https://software.opensuse.org/distributions/tumbleweed">OpenSUSE Tumbleweed</ulink>
|
||
rolling distribution</title>
|
||
|
||
<programlisting># zypper --root=/var/lib/machines/tumbleweed ar -c \
|
||
https://download.opensuse.org/tumbleweed/repo/oss tumbleweed
|
||
# zypper --root=/var/lib/machines/tumbleweed refresh
|
||
# zypper --root=/var/lib/machines/tumbleweed install --no-recommends \
|
||
systemd shadow zypper openSUSE-release vim
|
||
# systemd-nspawn -M tumbleweed passwd root
|
||
# systemd-nspawn -M tumbleweed -b</programlisting>
|
||
</example>
|
||
|
||
<example>
|
||
<title>Boot into an ephemeral snapshot of the host system</title>
|
||
|
||
<programlisting># systemd-nspawn -D / -xb</programlisting>
|
||
|
||
<para>This runs a copy of the host system in a snapshot which is removed immediately when the container
|
||
exits. All file system changes made during runtime will be lost on shutdown, hence.</para>
|
||
</example>
|
||
|
||
<example>
|
||
<title>Run a container with SELinux sandbox security contexts</title>
|
||
|
||
<programlisting># chcon system_u:object_r:svirt_sandbox_file_t:s0:c0,c1 -R /srv/container
|
||
# systemd-nspawn -L system_u:object_r:svirt_sandbox_file_t:s0:c0,c1 \
|
||
-Z system_u:system_r:svirt_lxc_net_t:s0:c0,c1 -D /srv/container /bin/sh</programlisting>
|
||
</example>
|
||
|
||
<example>
|
||
<title>Run a container with an OSTree deployment</title>
|
||
|
||
<programlisting># systemd-nspawn -b -i ~/image.raw \
|
||
--pivot-root=/ostree/deploy/$OS/deploy/$CHECKSUM:/sysroot \
|
||
--bind=+/sysroot/ostree/deploy/$OS/var:/var</programlisting>
|
||
</example>
|
||
</refsect1>
|
||
|
||
<refsect1>
|
||
<title>Exit status</title>
|
||
|
||
<para>The exit code of the program executed in the container is
|
||
returned.</para>
|
||
</refsect1>
|
||
|
||
<refsect1>
|
||
<title>See Also</title>
|
||
<para>
|
||
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
|
||
<citerefentry><refentrytitle>systemd.nspawn</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
|
||
<citerefentry project='man-pages'><refentrytitle>chroot</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
|
||
<citerefentry project='mankier'><refentrytitle>dnf</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
|
||
<citerefentry project='die-net'><refentrytitle>debootstrap</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
|
||
<citerefentry project='archlinux'><refentrytitle>pacman</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
|
||
<citerefentry project='mankier'><refentrytitle>zypper</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
|
||
<citerefentry><refentrytitle>systemd.slice</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
|
||
<citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
|
||
<citerefentry project='man-pages'><refentrytitle>btrfs</refentrytitle><manvolnum>8</manvolnum></citerefentry>
|
||
</para>
|
||
</refsect1>
|
||
|
||
</refentry>
|