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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
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  along with systemd; If not, see <http://www.gnu.org/licenses/>.
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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
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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
                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
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                <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>
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                <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
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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
                <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>
                containers.</para>
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                <para>Note that <command>systemd-nspawn</command> will
                mount file systems private to the container to
                <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
                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
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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
                share very few runtime objects except for the
                underlying file system.</para>
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                <para><command>systemd-nspawn</command> implements the
                <ulink
                url="http://www.freedesktop.org/wiki/Software/systemd/ContainerInterface">Container
                Interface</ulink> specification.</para>
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        </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>
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                                <term><option>-h</option></term>
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                                <listitem><para>Prints a short help
                                text and exits.</para></listitem>
                        </varlistentry>

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                        <varlistentry>
                                <term><option>--version</option></term>

                                <listitem><para>Prints a version string
                                and exits.</para></listitem>
                        </varlistentry>

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                        <varlistentry>
                                <term><option>--directory=</option></term>
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                                <term><option>-D</option></term>
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                                <listitem><para>Directory to use as
                                file system root for the namespace
                                container. If omitted the current
                                directory will be
                                used.</para></listitem>
                        </varlistentry>

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                        <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>

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                        <varlistentry>
                                <term><option>--user=</option></term>
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                                <term><option>-u</option></term>
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                                <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>

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                        <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>

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                        <varlistentry>
                                <term><option>--controllers=</option></term>
                                <term><option>-C</option></term>

                                <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.
                                </para></listitem>
                        </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
                                the container. This makes all network
                                interfaces unavailable in the
                                container, with the exception of the
                                loopback device.</para></listitem>
                        </varlistentry>

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                        <varlistentry>
                                <term><option>--read-only</option></term>

                                <listitem><para>Mount the root file
                                system read only for the
                                container.</para></listitem>
                        </varlistentry>

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                        <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><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
                                for more information. Note that the
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                                following capabilities will be granted
                                in any way: CAP_CHOWN,
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                                CAP_DAC_OVERRIDE, CAP_DAC_READ_SEARCH,
                                CAP_FOWNER, CAP_FSETID, CAP_IPC_OWNER,
                                CAP_KILL, CAP_LEASE,
                                CAP_LINUX_IMMUTABLE,
                                CAP_NET_BIND_SERVICE,
                                CAP_NET_BROADCAST, CAP_NET_RAW,
                                CAP_SETGID, CAP_SETFCAP, CAP_SETPCAP,
                                CAP_SETUID, CAP_SYS_ADMIN,
                                CAP_SYS_CHROOT, CAP_SYS_NICE,
                                CAP_SYS_PTRACE, CAP_SYS_TTY_CONFIG,
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                                CAP_SYS_RESOURCE, CAP_SYS_BOOT,
                                CAP_AUDIT_WRITE,
                                CAP_AUDIT_CONTROL.</para></listitem>
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                        </varlistentry>

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                        <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>guest</literal>,
                                <literal>auto</literal>. If
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                                <literal>no</literal>, the journal is
                                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
                                <filename>/var/log/journal/&lt;machine-id&gt;</filename>)
                                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
                                <filename>/var/log/journal/&lt;machine-id&gt;</filename>)
                                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),
                                and the right subdirectory of
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                                <filename>/var/log/journal</filename>
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                                exists, it will be bind mounted
                                into the container. If the
                                subdirectory doesn't exist, no
                                linking is performed. Effectively,
                                booting a container once with
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                                <literal>guest</literal> or
                                <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>
                                is used.</para></listitem>
                        </varlistentry>

                        <varlistentry>
                                <term><option>-j</option></term>

                                <listitem><para>Equivalent to
                                <option>--link-journal=guest</option>.</para></listitem>
                        </varlistentry>
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                </variablelist>

        </refsect1>

        <refsect1>
                <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
# 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>/srv/mycontainer/</filename> and
                then boots an OS in a namespace container in
                it.</para>
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        </refsect1>

        <refsect1>
                <title>Example 2</title>

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                <programlisting># debootstrap --arch=amd64 unstable ~/debian-tree/
# systemd-nspawn -D ~/debian-tree/</programlisting>
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                <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>
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        </refsect1>

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        <refsect1>
                <title>Example 3</title>

                <programlisting># pacstrap -c -d ~/arch-tree/ base
# systemd-nspawn -bD ~/arch-tree/</programlisting>

                <para>This installs a mimimal Arch Linux distribution into
                the directory <filename>~/arch-tree/</filename> and then
                boots an OS in a namespace container in it.</para>
        </refsect1>

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        <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>,
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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>
        </refsect1>

</refentry>