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