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systemd-stable/man/systemd-nspawn.xml
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<?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*-->
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
<!--
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<refentry id="systemd-nspawn"
xmlns:xi="http://www.w3.org/2001/XInclude">
<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</command>
<arg choice="opt" rep="repeat">OPTIONS</arg>
<arg choice="opt"><replaceable>COMMAND</replaceable>
<arg choice="opt" rep="repeat">ARGS</arg>
</arg>
</cmdsynopsis>
<cmdsynopsis>
<command>systemd-nspawn</command>
<arg choice="plain">-b</arg>
<arg choice="opt" rep="repeat">OPTIONS</arg>
<arg choice="opt" rep="repeat">ARGS</arg>
</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 project='man-pages'><refentrytitle>chroot</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
but more powerful since it fully virtualizes the file system
hierarchy, as well as the process tree, the various IPC subsystems
and the host and domain name.</para>
<para><command>systemd-nspawn</command> limits access to various
kernel interfaces in the container to read-only, such as
<filename>/sys</filename>, <filename>/proc/sys</filename> or
<filename>/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>
<para>Note that even though these security precautions are taken
<command>systemd-nspawn</command> is not suitable for fully 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.</para>
<para>In contrast to
<citerefentry project='man-pages'><refentrytitle>chroot</refentrytitle><manvolnum>1</manvolnum></citerefentry> <command>systemd-nspawn</command>
may be used to boot full Linux-based operating systems in a
container.</para>
<para>Use a tool like
<citerefentry project='mankier'><refentrytitle>dnf</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
<citerefentry project='die-net'><refentrytitle>yum</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
<citerefentry project='die-net'><refentrytitle>debootstrap</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
or
<citerefentry project='archlinux'><refentrytitle>pacman</refentrytitle><manvolnum>8</manvolnum></citerefentry>
to set up an OS directory tree suitable as file system hierarchy
for <command>systemd-nspawn</command> containers.</para>
<para>Note that <command>systemd-nspawn</command> will mount file
systems private to the container to <filename>/dev</filename>,
<filename>/run</filename> and similar. These will not be visible
outside of the container, and their contents will be lost when the
container exits.</para>
<para>Note that running two <command>systemd-nspawn</command>
containers from the same directory tree will not make processes in
them see each other. The PID namespace separation of the two
containers is complete and the containers will share very few
runtime objects except for the underlying file system. Use
<citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>'s
<command>login</command> command to request an additional login
prompt in a running container.</para>
<para><command>systemd-nspawn</command> implements the
<ulink
url="http://www.freedesktop.org/wiki/Software/systemd/ContainerInterface">Container
Interface</ulink> specification.</para>
<para>As a safety check <command>systemd-nspawn</command> will
verify the existence of <filename>/usr/lib/os-release</filename>
or <filename>/etc/os-release</filename> in the container tree
before starting the container (see
<citerefentry><refentrytitle>os-release</refentrytitle><manvolnum>5</manvolnum></citerefentry>).
It might be necessary to add this file to the container tree
manually if the OS of the container is too old to contain this
file out-of-the-box.</para>
</refsect1>
<refsect1>
<title>Options</title>
<para>If option <option>-b</option> is specified, the arguments
are used as arguments for the init binary. Otherwise,
<replaceable>COMMAND</replaceable> specifies the program to launch
in the container, and the remaining arguments are used as
arguments for this program. If <option>-b</option> is not used and
no arguments are specified, a shell is launched in the
container.</para>
<para>The following options are understood:</para>
<variablelist>
<varlistentry>
<term><option>-D</option></term>
<term><option>--directory=</option></term>
<listitem><para>Directory to use as file system root for the
container.</para>
<para>If neither <option>--directory=</option>, nor
<option>--image=</option> is specified the directory is
determined by searching for a directory named the same as the
machine name specified with <option>--machine=</option>. See
<citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
section "Files and Directories" for the precise search path.</para>
<para>If neither <option>--directory=</option>,
<option>--image=</option>, nor <option>--machine=</option>
are specified, the current directory will
be used. May not be specified together with
<option>--image=</option>.</para></listitem>
</varlistentry>
<varlistentry>
<term><option>--template=</option></term>
<listitem><para>Directory or <literal>btrfs</literal>
subvolume to use as template for the container's root
directory. If this is specified and the container's root
directory (as configured by <option>--directory=</option>)
does not yet exist it is created as <literal>btrfs</literal>
subvolume and populated from this template tree. Ideally, the
specified template path refers to the root of a
<literal>btrfs</literal> subvolume, in which case a simple
copy-on-write snapshot is taken, and populating the root
directory is instant. If the specified template path does not
refer to the root of a <literal>btrfs</literal> subvolume (or
not even to a <literal>btrfs</literal> file system at all),
the tree is copied, which can be substantially more
time-consuming. Note that if this option is used the
container's root directory (in contrast to the template
directory!) must be located on a <literal>btrfs</literal> file
system, so that the <literal>btrfs</literal> subvolume may be
created. May not be specified together with
<option>--image=</option> or
<option>--ephemeral</option>.</para>
<para>Note that this switch leaves host name, machine ID and
all other settings that could identify the instance
unmodified.</para></listitem>
</varlistentry>
<varlistentry>
<term><option>-x</option></term>
<term><option>--ephemeral</option></term>
<listitem><para>If specified, the container is run with a
temporary <literal>btrfs</literal> snapshot of its root
directory (as configured with <option>--directory=</option>),
that is removed immediately when the container terminates.
This option is only supported if the root file system is
<literal>btrfs</literal>. May not be specified together with
<option>--image=</option> or
<option>--template=</option>.</para>
<para>Note that this switch leaves host name, machine ID and
all other settings that could identify the instance
unmodified.</para></listitem>
</varlistentry>
<varlistentry>
<term><option>-i</option></term>
<term><option>--image=</option></term>
<listitem><para>Disk image to mount the root directory for the
container from. Takes a path to a regular file or to a block
device node. The file or block device must contain
either:</para>
<itemizedlist>
<listitem><para>An MBR partition table with a single
partition of type 0x83 that is marked
bootable.</para></listitem>
<listitem><para>A GUID partition table (GPT) with a single
partition of type
0fc63daf-8483-4772-8e79-3d69d8477de4.</para></listitem>
<listitem><para>A GUID partition table (GPT) with a marked
root partition which is mounted as the root directory of the
container. Optionally, GPT images may contain a home and/or
a server data partition which are mounted to the appropriate
places in the container. All these partitions must be
identified by the partition types defined by the <ulink
url="http://www.freedesktop.org/wiki/Specifications/DiscoverablePartitionsSpec/">Discoverable
Partitions Specification</ulink>.</para></listitem>
</itemizedlist>
<para>Any other partitions, such as foreign partitions, swap
partitions or EFI system partitions are not mounted. May not
be specified together with <option>--directory=</option>,
<option>--template=</option> or
<option>--ephemeral</option>.</para></listitem>
</varlistentry>
<varlistentry>
<term><option>-b</option></term>
<term><option>--boot</option></term>
<listitem><para>Automatically search for an init binary and
invoke it instead of a shell or a user supplied program. If
this option is used, arguments specified on the command line
are used as arguments for the init binary. This option may not
be combined with <option>--share-system</option>.
</para></listitem>
</varlistentry>
<varlistentry>
<term><option>-u</option></term>
<term><option>--user=</option></term>
<listitem><para>After transitioning into the container, change
to the specified user-defined in the container's user
database. Like all other systemd-nspawn features, this is not
a security feature and provides protection against accidental
destructive operations only.</para></listitem>
</varlistentry>
<varlistentry>
<term><option>-M</option></term>
<term><option>--machine=</option></term>
<listitem><para>Sets the machine name for this container. This
name may be used to identify this container during its runtime
(for example in tools like
<citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
and similar), and is used to initialize the container's
hostname (which the container can choose to override,
however). If not specified, the last component of the root
directory path of the container is used, possibly suffixed
with a random identifier in case <option>--ephemeral</option>
mode is selected. If the root directory selected is the host's
root directory the host's hostname is used as default
instead.</para></listitem>
</varlistentry>
<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>
<varlistentry>
<term><option>--slice=</option></term>
<listitem><para>Make the container part of the specified
slice, instead of the default
<filename>machine.slice</filename>. This is only applies if
the machine is run in its own scope unit, i.e. if
<option>--keep-unit</option> is not used.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>--property=</option></term>
<listitem><para>Set a unit property on the scope unit to
register for the machine. This only applies if the machine is
run in its own scope unit, i.e. if
<option>--keep-unit</option> is not used. Takes unit property
assignments in the same format as <command>systemctl
set-property</command>. This is useful to set memory limits
and similar for machines.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>--private-users=</option></term>
<listitem><para>Enables user namespacing. If enabled the
container will run with its own private set of Unix user and
group ids (UIDs and GIDs). Takes none, one or two
colon-separated parameters: the first parameter specifies the
first host UID to assign to the container, the second
parameter specifies the number of host UIDs to assign to the
container. If the second parameter is omitted, 65536 UIDs are
assigned. If the first parameter is also omitted (and hence
no parameter passed at all), the first UID assigned to the
container is read from the owner of the root directory of the
container's directory tree. By default no user namespacing is
applied.</para>
<para>Note that user namespacing currently requires OS trees
that are prepared for the UID shift that is being applied:
UIDs and GIDs used for file ownership or in file ACL entries
must be shifted to the container UID base that is
used during container runtime.</para>
<para>It is recommended to assign as least 65536 UIDs to each
container, so that the usable UID range in the container
covers 16bit. For best security do not assign overlapping UID
ranges to multiple containers. It is hence a good idea to use
the upper 16bit of the host 32bit UIDs as container
identifier, while the lower 16bit encode the container UID
used.</para>
<para>When user namespaces are used the GID range assigned to
each container is always chosen identical to the UID
range.</para></listitem>
</varlistentry>
<varlistentry>
<term><option>--private-network</option></term>
<listitem><para>Disconnect networking of the container from
the host. This makes all network interfaces unavailable in the
container, with the exception of the loopback device and those
specified with <option>--network-interface=</option> and
configured with <option>--network-veth</option>. If this
option is specified, the CAP_NET_ADMIN capability will be
added to the set of capabilities the container retains. The
latter may be disabled by using
<option>--drop-capability=</option>.</para></listitem>
</varlistentry>
<varlistentry>
<term><option>--network-interface=</option></term>
<listitem><para>Assign the specified network interface to the
container. This will remove the specified interface from the
calling namespace and place it in the container. When the
container terminates, it is moved back to the host namespace.
Note that <option>--network-interface=</option> implies
<option>--private-network</option>. This option may be used
more than once to add multiple network interfaces to the
container.</para></listitem>
</varlistentry>
<varlistentry>
<term><option>--network-macvlan=</option></term>
<listitem><para>Create a <literal>macvlan</literal> interface
of the specified Ethernet network interface and add it to the
container. A <literal>macvlan</literal> interface is a virtual
interface that adds a second MAC address to an existing
physical Ethernet link. The interface in the container will be
named after the interface on the host, prefixed with
<literal>mv-</literal>. Note that
<option>--network-macvlan=</option> implies
<option>--private-network</option>. This option may be used
more than once to add multiple network interfaces to the
container.</para></listitem>
</varlistentry>
<varlistentry>
<term><option>--network-ipvlan=</option></term>
<listitem><para>Create an <literal>ipvlan</literal> interface
of the specified Ethernet network interface and add it to the
container. An <literal>ipvlan</literal> interface is a virtual
interface, similar to a <literal>macvlan</literal> interface,
which uses the same MAC address as the underlying interface.
The interface in the container will be named after the
interface on the host, prefixed with <literal>iv-</literal>.
Note that <option>--network-ipvlan=</option> implies
<option>--private-network</option>. This option may be used
more than once to add multiple network interfaces to the
container.</para></listitem>
</varlistentry>
<varlistentry>
<term><option>-n</option></term>
<term><option>--network-veth</option></term>
<listitem><para>Create a virtual Ethernet link
(<literal>veth</literal>) between host and container. The host
side of the Ethernet link will be available as a network
interface named after the container's name (as specified with
<option>--machine=</option>), prefixed with
<literal>ve-</literal>. The container side of the Ethernet
link will be named <literal>host0</literal>. Note that
<option>--network-veth</option> implies
<option>--private-network</option>.</para></listitem>
</varlistentry>
<varlistentry>
<term><option>--network-bridge=</option></term>
<listitem><para>Adds the host side of the Ethernet link
created with <option>--network-veth</option> to the specified
bridge. Note that <option>--network-bridge=</option> implies
<option>--network-veth</option>. If this option is used, the
host side of the Ethernet link will use the
<literal>vb-</literal> prefix instead of
<literal>ve-</literal>.</para></listitem>
</varlistentry>
<varlistentry>
<term><option>-p</option></term>
<term><option>--port=</option></term>
<listitem><para>If private networking is enabled, maps an IP
port on the host onto an IP port on the container. Takes a
protocol specifier (either <literal>tcp</literal> or
<literal>udp</literal>), separated by a colon from a host port
number in the range 1 to 65535, separated by a colon from a
container port number in the range from 1 to 65535. The
protocol specifier and its separating colon may be omitted, in
which case <literal>tcp</literal> is assumed. The container
port number and its colon may be omitted, in which case the
same port as the host port is implied. This option is only
supported if private networking is used, such as
<option>--network-veth</option> or
<option>--network-bridge=</option>.</para></listitem>
</varlistentry>
<varlistentry>
<term><option>-Z</option></term>
<term><option>--selinux-context=</option></term>
<listitem><para>Sets the SELinux security context to be used
to label processes in the container.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-L</option></term>
<term><option>--selinux-apifs-context=</option></term>
<listitem><para>Sets the SELinux security context to be used
to label files in the virtual API file systems in the
container.</para>
</listitem>
</varlistentry>
<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 project='man-pages'><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
for more information. Note that the following capabilities
will be granted in any way: CAP_CHOWN, 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, CAP_SYS_RESOURCE, CAP_SYS_BOOT,
CAP_AUDIT_WRITE, CAP_AUDIT_CONTROL. Also CAP_NET_ADMIN is
retained if <option>--private-network</option> is specified.
If the special value <literal>all</literal> is passed, all
capabilities are retained.</para></listitem>
</varlistentry>
<varlistentry>
<term><option>--drop-capability=</option></term>
<listitem><para>Specify one or more additional capabilities to
drop for the container. This allows running the container with
fewer capabilities than the default (see
above).</para></listitem>
</varlistentry>
<varlistentry>
<term><option>--kill-signal=</option></term>
<listitem><para>Specify the process signal to send to the
container's PID 1 when nspawn itself receives SIGTERM, in
order to trigger an orderly shutdown of the
container. Defaults to SIGRTMIN+3 if <option>--boot</option>
is used (on systemd-compatible init systems SIGRTMIN+3
triggers an orderly shutdown). Takes a signal name like
<literal>SIGHUP</literal>, <literal>SIGTERM</literal> or
similar as argument.</para></listitem>
</varlistentry>
<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>try-host</literal>,
<literal>guest</literal>, <literal>try-guest</literal>,
<literal>auto</literal>. If <literal>no</literal>, the journal
is not linked. If <literal>host</literal>, the journal files
are stored on the host file system (beneath
<filename>/var/log/journal/<replaceable>machine-id</replaceable></filename>)
and the subdirectory is bind-mounted into the container at the
same location. If <literal>guest</literal>, the journal files
are stored on the guest file system (beneath
<filename>/var/log/journal/<replaceable>machine-id</replaceable></filename>)
and the subdirectory is symlinked into the host at the same
location. <literal>try-host</literal> and
<literal>try-guest</literal> do the same but do not fail if
the host does not have persistent journalling enabled. If
<literal>auto</literal> (the default), and the right
subdirectory of <filename>/var/log/journal</filename> exists,
it will be bind mounted into the container. If the
subdirectory does not exist, no linking is performed.
Effectively, booting a container once with
<literal>guest</literal> or <literal>host</literal> will link
the journal persistently if further on the default of
<literal>auto</literal> is used.</para></listitem>
</varlistentry>
<varlistentry>
<term><option>-j</option></term>
<listitem><para>Equivalent to
<option>--link-journal=try-guest</option>.</para></listitem>
</varlistentry>
<varlistentry>
<term><option>--read-only</option></term>
<listitem><para>Mount the root file system read-only for the
container.</para></listitem>
</varlistentry>
<varlistentry>
<term><option>--bind=</option></term>
<term><option>--bind-ro=</option></term>
<listitem><para>Bind mount a file or directory from the host
into the container. Takes one of: a path argument -- in which
case the specified path will be mounted from the host to the
same path in the container --, or a colon-separated pair of
paths -- in which case the first specified path is the source
in the host, and the second path is the destination in the
container --, or a colon-separated triple of source path,
destination path and mount options. Mount options are comma
separated and currently only "rbind" and "norbind"
are allowed. Defaults to "rbind". Backslash escapes are interpreted so
<literal>\:</literal> may be used to embed colons in either path.
This option may be specified multiple times for
creating multiple independent bind mount points. The
<option>--bind-ro=</option> option creates read-only bind
mounts.</para></listitem>
</varlistentry>
<varlistentry>
<term><option>--tmpfs=</option></term>
<listitem><para>Mount a tmpfs file system into the container.
Takes a single absolute path argument that specifies where to
mount the tmpfs instance to (in which case the directory
access mode will be chosen as 0755, owned by root/root), or
optionally a colon-separated pair of path and mount option
string, that is used for mounting (in which case the kernel
default for access mode and owner will be chosen, unless
otherwise specified). This option is particularly useful for
mounting directories such as <filename>/var</filename> as
tmpfs, to allow state-less systems, in particular when
combined with <option>--read-only</option>.
Backslash escapes are interpreted in the path so
<literal>\:</literal> may be used to embed colons in the path.
</para></listitem>
</varlistentry>
<varlistentry>
<term><option>--overlay=</option></term>
<term><option>--overlay-ro=</option></term>
<listitem><para>Combine multiple directory trees into one
overlay file system and mount it into the container. Takes a
list of colon-separated paths to the directory trees to
combine and the destination mount point.</para>
<para>Backslash escapes are interpreted in the paths, so
<literal>\:</literal> may be used to embed colons in the paths.
</para>
<para>If three or more paths are specified, then the last
specified path is the destination mount point in the
container, all paths specified before refer to directory trees
on the host and are combined in the specified order into one
overlay file system. The left-most path is hence the lowest
directory tree, the second-to-last path the highest directory
tree in the stacking order. If <option>--overlay-ro=</option>
is used instead of <option>--overlay=</option> a read-only
overlay file system is created. If a writable overlay file
system is created all changes made to it are written to the
highest directory tree in the stacking order, i.e. the
second-to-last specified.</para>
<para>If only two paths are specified, then the second
specified path is used both as the top-level directory tree in
the stacking order as seen from the host, as well as the mount
point for the overlay file system in the container. At least
two paths have to be specified.</para>
<para>For details about overlay file systems, see <ulink
url="https://www.kernel.org/doc/Documentation/filesystems/overlayfs.txt">overlayfs.txt</ulink>. Note
that the semantics of overlay file systems are substantially
different from normal file systems, in particular regarding
reported device and inode information. Device and inode
information may change for a file while it is being written
to, and processes might see out-of-date versions of files at
times. Note that this switch automatically derives the
<literal>workdir=</literal> mount option for the overlay file
system from the top-level directory tree, making it a sibling
of it. It is hence essential that the top-level directory tree
is not a mount point itself (since the working directory must
be on the same file system as the top-most directory
tree). Also note that the <literal>lowerdir=</literal> mount
option receives the paths to stack in the opposite order of
this switch.</para></listitem>
</varlistentry>
<varlistentry>
<term><option>--setenv=</option></term>
<listitem><para>Specifies an environment variable assignment
to pass to the init process in the container, in the format
<literal>NAME=VALUE</literal>. This may be used to override
the default variables or to set additional variables. This
parameter may be used more than once.</para></listitem>
</varlistentry>
<varlistentry>
<term><option>--share-system</option></term>
<listitem><para>Allows the container to share certain system
facilities with the host. More specifically, this turns off
PID namespacing, UTS namespacing and IPC namespacing, and thus
allows the guest to see and interact more easily with
processes outside of the container. Note that using this
option makes it impossible to start up a full Operating System
in the container, as an init system cannot operate in this
mode. It is only useful to run specific programs or
applications this way, without involving an init system in the
container. This option implies <option>--register=no</option>.
This option may not be combined with
<option>--boot</option>.</para></listitem>
</varlistentry>
<varlistentry>
<term><option>--register=</option></term>
<listitem><para>Controls whether the container is registered
with
<citerefentry><refentrytitle>systemd-machined</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
Takes a boolean argument, defaults to <literal>yes</literal>.
This option should be enabled when the container runs a full
Operating System (more specifically: an init system), and is
useful to ensure that the container is accessible via
<citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
and shown by tools such as
<citerefentry project='man-pages'><refentrytitle>ps</refentrytitle><manvolnum>1</manvolnum></citerefentry>.
If the container does not run an init system, it is
recommended to set this option to <literal>no</literal>. Note
that <option>--share-system</option> implies
<option>--register=no</option>. </para></listitem>
</varlistentry>
<varlistentry>
<term><option>--keep-unit</option></term>
<listitem><para>Instead of creating a transient scope unit to
run the container in, simply register the service or scope
unit <command>systemd-nspawn</command> has been invoked in
with
<citerefentry><refentrytitle>systemd-machined</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
This has no effect if <option>--register=no</option> is used.
This switch should be used if
<command>systemd-nspawn</command> is invoked from within a
service unit, and the service unit's sole purpose is to run a
single <command>systemd-nspawn</command> container. This
option is not available if run from a user
session.</para></listitem>
</varlistentry>
<varlistentry>
<term><option>--personality=</option></term>
<listitem><para>Control the architecture ("personality")
reported by
<citerefentry project='man-pages'><refentrytitle>uname</refentrytitle><manvolnum>2</manvolnum></citerefentry>
in the container. Currently, only <literal>x86</literal> and
<literal>x86-64</literal> are supported. This is useful when
running a 32-bit container on a 64-bit host. If this setting
is not used, the personality reported in the container is the
same as the one reported on the host.</para></listitem>
</varlistentry>
<varlistentry>
<term><option>-q</option></term>
<term><option>--quiet</option></term>
<listitem><para>Turns off any status output by the tool
itself. When this switch is used, the only output from nspawn
will be the console output of the container OS
itself.</para></listitem>
</varlistentry>
<varlistentry>
<term><option>--volatile</option></term>
<term><option>--volatile=</option><replaceable>MODE</replaceable></term>
<listitem><para>Boots the container in volatile mode. When no
mode parameter is passed or when mode is specified as
<option>yes</option> full volatile mode is enabled. This
means the root directory is mounted as mostly unpopulated
<literal>tmpfs</literal> instance, and
<filename>/usr</filename> from the OS tree is mounted into it,
read-only (the system thus starts up with read-only OS
resources, but pristine state and configuration, any changes
to the either are lost on shutdown). When the mode parameter
is specified as <option>state</option> the OS tree is
mounted read-only, but <filename>/var</filename> is mounted as
<literal>tmpfs</literal> instance into it (the system thus
starts up with read-only OS resources and configuration, but
pristine state, any changes to the latter are lost on
shutdown). When the mode parameter is specified as
<option>no</option> (the default) the whole OS tree is made
available writable.</para>
<para>Note that setting this to <option>yes</option> or
<option>state</option> will only work correctly with
operating systems in the container that can boot up with only
<filename>/usr</filename> mounted, and are able to populate
<filename>/var</filename> automatically, as
needed.</para></listitem>
</varlistentry>
<varlistentry>
<term><option>--settings=</option><replaceable>MODE</replaceable></term>
<listitem><para>Controls whether
<command>systemd-nspawn</command> shall search for and use
additional per-container settings from
<filename>.nspawn</filename> files. Takes a boolean or the
special values <option>override</option> or
<option>trusted</option>.</para>
<para>If enabled (the default) a settings file named after the
machine (as specified with the <option>--machine=</option>
setting, or derived from the directory or image file name)
with the suffix <filename>.nspawn</filename> is searched in
<filename>/etc/systemd/nspawn/</filename> and
<filename>/run/systemd/nspawn/</filename>. If it is found
there, its settings are read and used. If it is not found
there it is subsequently searched in the same directory as the
image file or in the immediate parent of the root directory of
the container. In this case, if the file is found its settings
will be also read and used, but potentially unsafe settings
are ignored. Note that in both these cases settings on the
command line take precedence over the corresponding settings
from loaded <filename>.nspawn</filename> files, if both are
specified. Unsafe settings are considered all settings that
elevate the container's privileges or grant access to
additional resources such as files or directories of the
host. For details about the format and contents of
<filename>.nspawn</filename> files consult
<citerefentry><refentrytitle>systemd.nspawn</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
<para>If this option is set to <option>override</option> the
file is searched, read and used the same way, however the order of
precedence is reversed: settings read from the
<filename>.nspawn</filename> file will take precedence over
the corresponding command line options, if both are
specified.</para>
<para>If this option is set to <option>trusted</option> the
file is searched, read and used the same way, but regardless
if found in <filename>/etc/systemd/nspawn/</filename>,
<filename>/run/systemd/nspawn/</filename> or next to the image
file or container root directory, all settings will take
effect, however command line arguments still take precedence
over corresponding settings.</para>
<para>If disabled no <filename>.nspawn</filename> file is read
and no settings except the ones on the command line are in
effect.</para></listitem>
</varlistentry>
<xi:include href="standard-options.xml" xpointer="help" />
<xi:include href="standard-options.xml" xpointer="version" />
</variablelist>
</refsect1>
<refsect1>
<title>Examples</title>
<example>
<title>Download a Fedora image and start a shell in it</title>
<programlisting># machinectl pull-raw --verify=no http://ftp.halifax.rwth-aachen.de/fedora/linux/releases/21/Cloud/Images/x86_64/Fedora-Cloud-Base-20141203-21.x86_64.raw.xz
# systemd-nspawn -M Fedora-Cloud-Base-20141203-21</programlisting>
<para>This downloads an image using
<citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
and opens a shell in it.</para>
</example>
<example>
<title>Build and boot a minimal Fedora distribution in a container</title>
<programlisting># dnf -y --releasever=21 --nogpg --installroot=/srv/mycontainer --disablerepo='*' --enablerepo=fedora install systemd passwd dnf fedora-release vim-minimal
# systemd-nspawn -bD /srv/mycontainer</programlisting>
<para>This installs a minimal Fedora distribution into the
directory <filename noindex='true'>/srv/mycontainer/</filename>
and then boots an OS in a namespace container in it.</para>
</example>
<example>
<title>Spawn a shell in a container of a minimal Debian unstable distribution</title>
<programlisting># debootstrap --arch=amd64 unstable ~/debian-tree/
# systemd-nspawn -D ~/debian-tree/</programlisting>
<para>This installs a minimal Debian unstable distribution into
the directory <filename>~/debian-tree/</filename> and then
spawns a shell in a namespace container in it.</para>
</example>
<example>
<title>Boot a minimal Arch Linux distribution in a container</title>
<programlisting># pacstrap -c -d ~/arch-tree/ base
# systemd-nspawn -bD ~/arch-tree/</programlisting>
<para>This installs a minimal Arch Linux distribution into the
directory <filename>~/arch-tree/</filename> and then boots an OS
in a namespace container in it.</para>
</example>
<example>
<title>Boot into an ephemeral <literal>btrfs</literal> snapshot of the host system</title>
<programlisting># systemd-nspawn -D / -xb</programlisting>
<para>This runs a copy of the host system in a
<literal>btrfs</literal> snapshot which is removed immediately
when the container exits. All file system changes made during
runtime will be lost on shutdown, hence.</para>
</example>
<example>
<title>Run a container with SELinux sandbox security contexts</title>
<programlisting># chcon system_u:object_r:svirt_sandbox_file_t:s0:c0,c1 -R /srv/container
# systemd-nspawn -L system_u:object_r:svirt_sandbox_file_t:s0:c0,c1 -Z system_u:system_r:svirt_lxc_net_t:s0:c0,c1 -D /srv/container /bin/sh</programlisting>
</example>
</refsect1>
<refsect1>
<title>Exit status</title>
<para>The exit code of the program executed in the container is
returned.</para>
</refsect1>
<refsect1>
<title>See Also</title>
<para>
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.nspawn</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry project='man-pages'><refentrytitle>chroot</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry project='mankier'><refentrytitle>dnf</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
<citerefentry project='die-net'><refentrytitle>yum</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
<citerefentry project='die-net'><refentrytitle>debootstrap</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
<citerefentry project='archlinux'><refentrytitle>pacman</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.slice</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry project='man-pages'><refentrytitle>btrfs</refentrytitle><manvolnum>8</manvolnum></citerefentry>
</para>
</refsect1>
</refentry>
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