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451 lines
22 KiB
XML
451 lines
22 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</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>
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</arg>
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</cmdsynopsis>
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<cmdsynopsis>
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<command>systemd-nspawn</command>
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<arg choice="plain">-b</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
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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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<citerefentry><refentrytitle>debootstrap</refentrytitle><manvolnum>8</manvolnum></citerefentry>
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or
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<citerefentry><refentrytitle>pacman</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. It is however possible to
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enter an existing container, see
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<link linkend='example-nsenter'>Example 4</link> below.
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</para>
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<para><command>systemd-nspawn</command> implements the
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<ulink
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url="http://www.freedesktop.org/wiki/Software/systemd/ContainerInterface">Container
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Interface</ulink> specification.</para>
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<para>As a safety check
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<command>systemd-nspawn</command> will verify the
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existence of <filename>/etc/os-release</filename> in
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the container tree before starting the container (see
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<citerefentry><refentrytitle>os-release</refentrytitle><manvolnum>5</manvolnum></citerefentry>). It
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might be necessary to add this file to the container
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tree manually if the OS of the container is too old to
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contain this file out-of-the-box.</para>
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</refsect1>
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<refsect1>
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<title>Incompatibility with Auditing</title>
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<para>Note that the kernel auditing subsystem is
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currently broken when used together with
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containers. We hence recommend turning it off entirely
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by booting with <literal>audit=0</literal> on the
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kernel command line, or by turning it off at kernel
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build time. If auditing is enabled in the kernel
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operating systems booted in an nspawn container might
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refuse log-in attempts.</para>
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</refsect1>
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<refsect1>
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<title>Options</title>
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<para>If option <option>-b</option> is specified, the
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arguments are used as arguments for the init
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binary. Otherwise, <replaceable>COMMAND</replaceable>
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specifies the program to launch in the container, and
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the remaining arguments are used as arguments for this
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program. If <option>-b</option> is not used and no
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arguments are specifed, 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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<varlistentry>
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<term><option>-h</option></term>
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<term><option>--help</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>--version</option></term>
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<listitem><para>Prints a version string
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and exits.</para></listitem>
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</varlistentry>
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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
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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>-b</option></term>
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<term><option>--boot</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. If this option is used, arguments
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specified on the command line are used
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as arguments for the init binary.
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</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><option>-u</option></term>
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<term><option>--user=</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>-M</option></term>
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<term><option>--machine=</option></term>
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<listitem><para>Sets the machine name
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for this container. This name may be
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used to identify this container on the
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host, and is used to initialize the
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container's hostname (which the
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container can choose to override,
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however). If not specified the last
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component of the root directory of the
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container is used.</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>-C</option></term>
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<term><option>--controllers=</option></term>
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<listitem><para>Makes the container appear in
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other hierarchies than 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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<varlistentry>
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<term><option>--capability=</option></term>
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<listitem><para>List one or more
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additional capabilities to grant the
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container. Takes a comma-separated
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list of capability names, see
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<citerefentry><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
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for more information. Note that the
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following capabilities will be granted
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in any way: CAP_CHOWN,
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CAP_DAC_OVERRIDE, CAP_DAC_READ_SEARCH,
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CAP_FOWNER, CAP_FSETID, CAP_IPC_OWNER,
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CAP_KILL, CAP_LEASE,
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CAP_LINUX_IMMUTABLE,
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CAP_NET_BIND_SERVICE,
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CAP_NET_BROADCAST, CAP_NET_RAW,
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CAP_SETGID, CAP_SETFCAP, CAP_SETPCAP,
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CAP_SETUID, CAP_SYS_ADMIN,
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CAP_SYS_CHROOT, CAP_SYS_NICE,
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CAP_SYS_PTRACE, CAP_SYS_TTY_CONFIG,
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CAP_SYS_RESOURCE, CAP_SYS_BOOT,
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CAP_AUDIT_WRITE,
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CAP_AUDIT_CONTROL.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--link-journal=</option></term>
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<listitem><para>Control whether the
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container's journal shall be made
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visible to the host system. If enabled
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allows viewing the container's journal
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files from the host (but not vice
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versa). Takes one of
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<literal>no</literal>,
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<literal>host</literal>,
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<literal>guest</literal>,
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<literal>auto</literal>. If
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<literal>no</literal>, the journal is
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not linked. If <literal>host</literal>,
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the journal files are stored on the
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host file system (beneath
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<filename>/var/log/journal/<replaceable>machine-id</replaceable></filename>)
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and the subdirectory is bind-mounted
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into the container at the same
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location. If <literal>guest</literal>,
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the journal files are stored on the
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guest file system (beneath
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<filename>/var/log/journal/<replaceable>machine-id</replaceable></filename>)
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and the subdirectory is symlinked into the host
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at the same location. If
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<literal>auto</literal> (the default),
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and the right subdirectory of
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<filename>/var/log/journal</filename>
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exists, it will be bind mounted
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into the container. If the
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subdirectory doesn't exist, no
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linking is performed. Effectively,
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booting a container once with
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<literal>guest</literal> or
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<literal>host</literal> will link the
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journal persistently if further on
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the default of <literal>auto</literal>
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is used.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><option>-j</option></term>
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<listitem><para>Equivalent to
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<option>--link-journal=guest</option>.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--bind=</option></term>
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<term><option>--bind-ro=</option></term>
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<listitem><para>Bind mount a file or
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directory from the host into the
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container. Either takes a path
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argument -- in which case the
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specified path will be mounted from
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the host to the same path in the
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container --, or a colon-separated
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pair of paths -- in which case the
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first specified path is the source in
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the host, and the second path is the
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destination in the container. The
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<option>--bind-ro=</option> option
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creates read-only bind
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mount.</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 -y --releasever=19 --nogpg --installroot=/srv/mycontainer --disablerepo='*' --enablerepo=fedora install systemd passwd yum fedora-release vim-minimal
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# systemd-nspawn -bD /srv/mycontainer</programlisting>
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<para>This installs a minimal Fedora distribution into
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the directory <filename noindex='true'>/srv/mycontainer/</filename> and
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then boots an OS in a namespace container in
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it.</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>Example 3</title>
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<programlisting># pacstrap -c -d ~/arch-tree/ base
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# systemd-nspawn -bD ~/arch-tree/</programlisting>
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<para>This installs a mimimal Arch Linux distribution into
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the directory <filename>~/arch-tree/</filename> and then
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boots an OS in a namespace container in it.</para>
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</refsect1>
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<refsect1 id='example-nsenter'>
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<title>Example 4</title>
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<para>To enter the container, PID of one of the
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processes sharing the new namespaces must be used.
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<command>systemd-nspawn</command> prints the PID
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(as viewed from the outside) of the launched process,
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and it can be used to enter the container.</para>
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<programlisting># nsenter -m -u -i -n -p -t $PID</programlisting>
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<para><citerefentry><refentrytitle>nsenter</refentrytitle><manvolnum>1</manvolnum></citerefentry>
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is part of
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<ulink url="https://github.com/karelzak/util-linux">util-linux</ulink>.
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Kernel support for entering namespaces was added in
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Linux 3.8.</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>unshare</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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<citerefentry><refentrytitle>pacman</refentrytitle><manvolnum>8</manvolnum></citerefentry>
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</para>
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</refsect1>
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</refentry>
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