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<?xml version='1.0'?> <!--*-nxml-*-->
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
<!--
This file is part of systemd.
Copyright 2010 Lennart Poettering
systemd is free software; you can redistribute it and/or modify it
under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version.
systemd is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with systemd; If not, see <http://www.gnu.org/licenses/>.
-->
<refentry id="systemd-nspawn">
<refentryinfo>
<title>systemd-nspawn</title>
<productname>systemd</productname>
<authorgroup>
<author>
<contrib>Developer</contrib>
<firstname>Lennart</firstname>
<surname>Poettering</surname>
<email>lennart@poettering.net</email>
</author>
</authorgroup>
</refentryinfo>
<refmeta>
<refentrytitle>systemd-nspawn</refentrytitle>
<manvolnum>1</manvolnum>
</refmeta>
<refnamediv>
<refname>systemd-nspawn</refname>
<refpurpose>Spawn a namespace container for debugging, testing and building</refpurpose>
</refnamediv>
<refsynopsisdiv>
<cmdsynopsis>
<command>systemd-nspawn <arg choice="opt" rep="repeat">OPTIONS</arg> <arg choice="opt">COMMAND</arg> <arg choice="opt" rep="repeat">ARGS</arg></command>
</cmdsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para><command>systemd-nspawn</command> may be used to
run a command or OS in a light-weight namespace
container. In many ways it is similar to
<citerefentry><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 the host and domain
name.</para>
<para><command>systemd-nspawn</command> limits access
to various kernel interfaces in the container to
read-only, such as <filename>/sys</filename>,
<filename>/proc/sys</filename> or
<filename>/sys/fs/selinux</filename>. Network
interfaces and the system clock may not be changed
from within the container. Device nodes may not be
created. The host system cannot be rebooted and kernel
modules may not be loaded from within the
container.</para>
<para>Note that even though these security precautions
are taken <command>systemd-nspawn</command> is not
suitable for secure container setups. Many of the
security features may be circumvented and are hence
primarily useful to avoid accidental changes to the
host system from the container. The intended use of
this program is debugging and testing as well as
building of packages, distributions and software
involved with boot and systems management.</para>
<para>In contrast to
<citerefentry><refentrytitle>chroot</refentrytitle><manvolnum>1</manvolnum></citerefentry>
<command>systemd-nspawn</command> may be used to boot
full Linux-based operating systems in a
container.</para>
<para>Use a tool like
<citerefentry><refentrytitle>yum</refentrytitle><manvolnum>8</manvolnum></citerefentry>
or
<citerefentry><refentrytitle>debootstrap</refentrytitle><manvolnum>8</manvolnum></citerefentry>
to set up an OS directory tree suitable as file system
hierarchy for <command>systemd-nspawn</command>
containers.</para>
<para>Note that <command>systemd-nspawn</command> will
mount file systems private to the container to
<filename>/dev</filename>,
<filename>/run</filename> and similar. These will
not be visible outside of the 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 processes in them
see each other. The PID namespace separation of the
two containers is complete and the containers will
share very few runtime objects except for the
underlying file system.</para>
</refsect1>
<refsect1>
<title>Options</title>
<para>If no arguments are passed the container is set
up and a shell started in it, otherwise the passed
command and arguments are executed in it. The
following options are understood:</para>
<variablelist>
<varlistentry>
<term><option>--help</option></term>
<term><option>-h</option></term>
<listitem><para>Prints a short help
text and exits.</para></listitem>
</varlistentry>
<varlistentry>
<term><option>--directory=</option></term>
<term><option>-D</option></term>
<listitem><para>Directory to use as
file system root for the namespace
container. If omitted the current
directory will be
used.</para></listitem>
</varlistentry>
<varlistentry>
<term><option>--boot</option></term>
<term><option>-b</option></term>
<listitem><para>Automatically search
for an init binary and invoke it
instead of a shell or a user supplied
program.</para></listitem>
</varlistentry>
<varlistentry>
<term><option>--user=</option></term>
<term><option>-u</option></term>
<listitem><para>Run the command
under specified user, create home
directory and cd into it. As rest
of systemd-nspawn, this is not
the security feature and limits
against accidental changes only.
</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.
</para></listitem>
</varlistentry>
<varlistentry>
<term><option>--controllers=</option></term>
<term><option>-C</option></term>
<listitem><para>Makes the container appear in
other hierarchies that the name=systemd:/ one.
Takes a comma-separated list of controllers.
</para></listitem>
</varlistentry>
<varlistentry>
<term><option>--private-network</option></term>
<listitem><para>Turn off networking in
the container. This makes all network
interfaces unavailable in the
container, with the exception of the
loopback device.</para></listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Example 1</title>
<programlisting># yum --releasever=17 --nogpgcheck --installroot ~/fedora-tree/ install yum passwd vim-minimal rootfiles systemd
# systemd-nspawn -D ~/fedora-tree /usr/lib/systemd/systemd</programlisting>
<para>This installs a minimal Fedora distribution into
the directory <filename>~/fedora-tree/</filename>
and then boots an OS in a namespace container in it,
with systemd as init system.</para>
</refsect1>
<refsect1>
<title>Example 2</title>
<programlisting># debootstrap --arch=amd64 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 in a namespace container in it.</para>
</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>chroot</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>yum</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
<citerefentry><refentrytitle>debootstrap</refentrytitle><manvolnum>8</manvolnum></citerefentry>
</para>
</refsect1>
</refentry>
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