Commit 8f7a3c14 authored by Lennart Poettering's avatar Lennart Poettering
Browse files

man: document systemd-nspawn

parent b9a8e638
......@@ -519,6 +519,7 @@ MANPAGES = \
man/systemctl.1 \
man/systemadm.1 \
man/systemd-cgls.1 \
man/systemd-nspawn.1 \
man/systemd-tmpfiles.8 \
man/systemd-notify.1 \
man/sd_notify.3 \
......
<?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">
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Copyright 2010 Lennart Poettering
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<refentry id="systemd-nspawn">
<refentryinfo>
<title>systemd-nspawn</title>
<productname>systemd</productname>
<authorgroup>
<author>
<contrib>Developer</contrib>
<firstname>Lennart</firstname>
<surname>Poettering</surname>
<email>lennart@poettering.net</email>
</author>
</authorgroup>
</refentryinfo>
<refmeta>
<refentrytitle>systemd-nspawn</refentrytitle>
<manvolnum>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 hierachy, 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>/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>debootstrap</refentrytitle><manvolnum>8</manvolnum></citerefentry> or <citerefentry><refentrytitle>mock</refentrytitle><manvolnum>1</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>/dev/.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 seperation 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>
<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>
</variablelist>
</refsect1>
<refsect1>
<title>Example 1</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>Example 2</title>
<programlisting># mock --init
# systemd-nspawn -D /var/lib/mock/fedora-rawhide-x86_64/root/ /bin/systemd systemd.log_level=debug</programlisting>
<para>This installs a minimal Fedora distribution into
a subdirectory of <filename>/var/lib/mock/</filename>
and then boots an OS in a namespace container in it,
with systemd as init system, configured for debug
logging.</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>debootstrap</refentrytitle><manvolnum>8</manvolnum></citerefentry>
<citerefentry><refentrytitle>mock</refentrytitle><manvolnum>1</manvolnum></citerefentry>
</para>
</refsect1>
</refentry>
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