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</style><a href="index.html">Index </a>·
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<a href="systemd.directives.html">Directives </a>·
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<a href="../python-systemd/index.html">Python </a>·
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<a href="../libudev/index.html">libudev </a>·
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<a href="../libudev/index.html">gudev </a><span style="float:right">systemd 208</span><hr><div class="refentry"><a name="systemd-nspawn"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>systemd-nspawn — Spawn a namespace container for debugging, testing and building</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><div class="cmdsynopsis"><p><code class="command">systemd-nspawn</code> [OPTIONS...] [<em class="replaceable"><code>COMMAND</code></em>
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[ARGS...]
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]</p></div><div class="cmdsynopsis"><p><code class="command">systemd-nspawn</code> -b [OPTIONS...] [ARGS...]</p></div></div><div class="refsect1"><a name="idm274694735024"></a><h2 id="Description">Description<a class="headerlink" title="Permalink to this headline" href="#Description">¶</a></h2><p><span class="command"><strong>systemd-nspawn</strong></span> 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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<a href="chroot.html"><span class="citerefentry"><span class="refentrytitle">chroot</span>(1)</span></a>,
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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.</p><p><span class="command"><strong>systemd-nspawn</strong></span> limits access
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to various kernel interfaces in the container to
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read-only, such as <code class="filename">/sys</code>,
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<code class="filename">/proc/sys</code> or
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<code class="filename">/sys/fs/selinux</code>. 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.</p><p>Note that even though these security precautions
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are taken <span class="command"><strong>systemd-nspawn</strong></span> 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.</p><p>In contrast to
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<a href="chroot.html"><span class="citerefentry"><span class="refentrytitle">chroot</span>(1)</span></a> <span class="command"><strong>systemd-nspawn</strong></span>
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may be used to boot full Linux-based operating systems
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in a container.</p><p>Use a tool like
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<a href="yum.html"><span class="citerefentry"><span class="refentrytitle">yum</span>(8)</span></a>,
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<a href="debootstrap.html"><span class="citerefentry"><span class="refentrytitle">debootstrap</span>(8)</span></a>,
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or
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<a href="pacman.html"><span class="citerefentry"><span class="refentrytitle">pacman</span>(8)</span></a>
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to set up an OS directory tree suitable as file system
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hierarchy for <span class="command"><strong>systemd-nspawn</strong></span>
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containers.</p><p>Note that <span class="command"><strong>systemd-nspawn</strong></span> will
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mount file systems private to the container to
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<code class="filename">/dev</code>,
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<code class="filename">/run</code> 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.</p><p>Note that running two
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<span class="command"><strong>systemd-nspawn</strong></span> 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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<a class="link" href="#example-nsenter" title="Example 4">Example 4</a> below.
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</p><p><span class="command"><strong>systemd-nspawn</strong></span> implements the
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<a class="ulink" href="http://www.freedesktop.org/wiki/Software/systemd/ContainerInterface" target="_top">Container
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Interface</a> specification.</p><p>As a safety check
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<span class="command"><strong>systemd-nspawn</strong></span> will verify the
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existence of <code class="filename">/etc/os-release</code> in
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the container tree before starting the container (see
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<a href="os-release.html"><span class="citerefentry"><span class="refentrytitle">os-release</span>(5)</span></a>). 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.</p></div><div class="refsect1"><a name="idm274698612992"></a><h2 id="Incompatibility with Auditing">Incompatibility with Auditing<a class="headerlink" title="Permalink to this headline" href="#Incompatibility%20with%20Auditing">¶</a></h2><p>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 "<code class="literal">audit=0</code>" 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.</p></div><div class="refsect1"><a name="idm274698590992"></a><h2 id="Options">Options<a class="headerlink" title="Permalink to this headline" href="#Options">¶</a></h2><p>If option <code class="option">-b</code> is specified, the
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arguments are used as arguments for the init
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binary. Otherwise, <em class="replaceable"><code>COMMAND</code></em>
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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 <code class="option">-b</code> is not used and no
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arguments are specifed, a shell is launched in the
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container.</p><p>The following options are understood:</p><div class="variablelist"><dl class="variablelist"><dt id="-h"><span class="term"><code class="option">-h</code>, </span><span class="term"><code class="option">--help</code></span><a class="headerlink" title="Permalink to this term" href="#-h">¶</a></dt><dd><p>Prints a short help
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text and exits.</p></dd><dt id="--version"><span class="term"><code class="option">--version</code></span><a class="headerlink" title="Permalink to this term" href="#--version">¶</a></dt><dd><p>Prints a version string
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and exits.</p></dd><dt id="-D"><span class="term"><code class="option">-D</code>, </span><span class="term"><code class="option">--directory=</code></span><a class="headerlink" title="Permalink to this term" href="#-D">¶</a></dt><dd><p>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.</p></dd><dt id="-b"><span class="term"><code class="option">-b</code>, </span><span class="term"><code class="option">--boot</code></span><a class="headerlink" title="Permalink to this term" href="#-b">¶</a></dt><dd><p>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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</p></dd><dt id="-u"><span class="term"><code class="option">-u</code>, </span><span class="term"><code class="option">--user=</code></span><a class="headerlink" title="Permalink to this term" href="#-u">¶</a></dt><dd><p>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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</p></dd><dt id="-M"><span class="term"><code class="option">-M</code>, </span><span class="term"><code class="option">--machine=</code></span><a class="headerlink" title="Permalink to this term" href="#-M">¶</a></dt><dd><p>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.</p></dd><dt id="--slice="><span class="term"><code class="option">--slice=</code></span><a class="headerlink" title="Permalink to this term" href="#--slice=">¶</a></dt><dd><p>Make the container
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part of the specified slice, instead
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of the
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<code class="filename">machine.slice</code>.</p></dd><dt id="--uuid="><span class="term"><code class="option">--uuid=</code></span><a class="headerlink" title="Permalink to this term" href="#--uuid=">¶</a></dt><dd><p>Set the specified UUID
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for the container. The init system
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will initialize
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<code class="filename">/etc/machine-id</code>
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from this if this file is not set yet.
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</p></dd><dt id="--private-network"><span class="term"><code class="option">--private-network</code></span><a class="headerlink" title="Permalink to this term" href="#--private-network">¶</a></dt><dd><p>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.</p></dd><dt id="--read-only"><span class="term"><code class="option">--read-only</code></span><a class="headerlink" title="Permalink to this term" href="#--read-only">¶</a></dt><dd><p>Mount the root file
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system read-only for the
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container.</p></dd><dt id="--capability="><span class="term"><code class="option">--capability=</code></span><a class="headerlink" title="Permalink to this term" href="#--capability=">¶</a></dt><dd><p>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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<a href="capabilities.html"><span class="citerefentry"><span class="refentrytitle">capabilities</span>(7)</span></a>
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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.</p></dd><dt id="--link-journal="><span class="term"><code class="option">--link-journal=</code></span><a class="headerlink" title="Permalink to this term" href="#--link-journal=">¶</a></dt><dd><p>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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"<code class="literal">no</code>",
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"<code class="literal">host</code>",
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"<code class="literal">guest</code>",
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"<code class="literal">auto</code>". If
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"<code class="literal">no</code>", the journal is
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not linked. If "<code class="literal">host</code>",
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the journal files are stored on the
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host file system (beneath
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<code class="filename">/var/log/journal/<em class="replaceable"><code>machine-id</code></em></code>)
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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 "<code class="literal">guest</code>",
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the journal files are stored on the
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guest file system (beneath
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<code class="filename">/var/log/journal/<em class="replaceable"><code>machine-id</code></em></code>)
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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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"<code class="literal">auto</code>" (the default),
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and the right subdirectory of
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<code class="filename">/var/log/journal</code>
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exists, it will be bind mounted
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into the container. If the
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subdirectory does not exist, no
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linking is performed. Effectively,
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booting a container once with
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"<code class="literal">guest</code>" or
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"<code class="literal">host</code>" will link the
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journal persistently if further on
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the default of "<code class="literal">auto</code>"
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is used.</p></dd><dt id="-j"><span class="term"><code class="option">-j</code></span><a class="headerlink" title="Permalink to this term" href="#-j">¶</a></dt><dd><p>Equivalent to
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<code class="option">--link-journal=guest</code>.</p></dd><dt id="--bind="><span class="term"><code class="option">--bind=</code>, </span><span class="term"><code class="option">--bind-ro=</code></span><a class="headerlink" title="Permalink to this term" href="#--bind=">¶</a></dt><dd><p>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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<code class="option">--bind-ro=</code> option
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creates read-only bind
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mount.</p></dd></dl></div></div><div class="refsect1"><a name="idm274693634016"></a><h2 id="Example 1">Example 1<a class="headerlink" title="Permalink to this headline" href="#Example%201">¶</a></h2><pre class="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</pre><p>This installs a minimal Fedora distribution into
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the directory <code class="filename">/srv/mycontainer/</code> and
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then boots an OS in a namespace container in
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it.</p></div><div class="refsect1"><a name="idm274693631168"></a><h2 id="Example 2">Example 2<a class="headerlink" title="Permalink to this headline" href="#Example%202">¶</a></h2><pre class="programlisting"># debootstrap --arch=amd64 unstable ~/debian-tree/
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# systemd-nspawn -D ~/debian-tree/</pre><p>This installs a minimal Debian unstable
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distribution into the directory
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<code class="filename">~/debian-tree/</code> and then spawns a
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shell in a namespace container in it.</p></div><div class="refsect1"><a name="idm274693628448"></a><h2 id="Example 3">Example 3<a class="headerlink" title="Permalink to this headline" href="#Example%203">¶</a></h2><pre class="programlisting"># pacstrap -c -d ~/arch-tree/ base
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# systemd-nspawn -bD ~/arch-tree/</pre><p>This installs a mimimal Arch Linux distribution into
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the directory <code class="filename">~/arch-tree/</code> and then
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boots an OS in a namespace container in it.</p></div><div class="refsect1"><a name="example-nsenter"></a><h2 id="Example 4">Example 4<a class="headerlink" title="Permalink to this headline" href="#Example%204">¶</a></h2><p>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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<span class="command"><strong>systemd-nspawn</strong></span> 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.</p><pre class="programlisting"># nsenter -m -u -i -n -p -t $PID</pre><p><a href="nsenter.html"><span class="citerefentry"><span class="refentrytitle">nsenter</span>(1)</span></a>
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is part of
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<a class="ulink" href="https://github.com/karelzak/util-linux" target="_top">util-linux</a>.
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Kernel support for entering namespaces was added in
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Linux 3.8.</p></div><div class="refsect1"><a name="idm274693621248"></a><h2 id="Exit status">Exit status<a class="headerlink" title="Permalink to this headline" href="#Exit%20status">¶</a></h2><p>The exit code of the program executed in the
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container is returned.</p></div><div class="refsect1"><a name="idm274693620000"></a><h2 id="See Also">See Also<a class="headerlink" title="Permalink to this headline" href="#See%20Also">¶</a></h2><p>
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<a href="systemd.html"><span class="citerefentry"><span class="refentrytitle">systemd</span>(1)</span></a>,
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<a href="chroot.html"><span class="citerefentry"><span class="refentrytitle">chroot</span>(1)</span></a>,
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<a href="unshare.html"><span class="citerefentry"><span class="refentrytitle">unshare</span>(1)</span></a>,
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<a href="yum.html"><span class="citerefentry"><span class="refentrytitle">yum</span>(8)</span></a>,
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<a href="debootstrap.html"><span class="citerefentry"><span class="refentrytitle">debootstrap</span>(8)</span></a>,
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<a href="pacman.html"><span class="citerefentry"><span class="refentrytitle">pacman</span>(8)</span></a>,
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<a href="systemd.slice.html"><span class="citerefentry"><span class="refentrytitle">systemd.slice</span>(5)</span></a>
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</p></div></div></body></html>
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