a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster<?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*-->

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"

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a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster<refentry id="systemd-nspawn"

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster xmlns:xi="http://www.w3.org/2001/XInclude">

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster <refentryinfo>

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster <title>systemd-nspawn</title>

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster <productname>systemd</productname>

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster <authorgroup>

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster <author>

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster <contrib>Developer</contrib>

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster <firstname>Lennart</firstname>

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster <surname>Poettering</surname>

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster <email>lennart@poettering.net</email>

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster </author>

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster </authorgroup>

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster </refentryinfo>

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster <refmeta>

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster <refentrytitle>systemd-nspawn</refentrytitle>

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster <manvolnum>1</manvolnum>

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster </refmeta>

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster <refnamediv>

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster <refname>systemd-nspawn</refname>

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster <refpurpose>Spawn a namespace container for debugging, testing and building</refpurpose>

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster </refnamediv>

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster <refsynopsisdiv>

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster <cmdsynopsis>

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster <command>systemd-nspawn</command>

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster <arg choice="opt" rep="repeat">OPTIONS</arg>

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster <arg choice="opt"><replaceable>COMMAND</replaceable>

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster <arg choice="opt" rep="repeat">ARGS</arg>

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster </arg>

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster </cmdsynopsis>

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster <cmdsynopsis>

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster <command>systemd-nspawn</command>

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster <arg choice="plain">-b</arg>

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster <arg choice="opt" rep="repeat">OPTIONS</arg>

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster <arg choice="opt" rep="repeat">ARGS</arg>

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster </cmdsynopsis>

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster </refsynopsisdiv>

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster <refsect1>

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster <title>Description</title>

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster <para><command>systemd-nspawn</command> may be used to run a

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster command or OS in a light-weight namespace container. In many ways

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster it is similar to

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster <citerefentry project='man-pages'><refentrytitle>chroot</refentrytitle><manvolnum>1</manvolnum></citerefentry>,

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster but more powerful since it fully virtualizes the file system

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster 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>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 at least 65536 UIDs to each

container, so that the usable UID range in the container

covers 16 bit. For best security, do not assign overlapping UID

ranges to multiple containers. It is hence a good idea to use

the upper 16 bit of the host 32-bit UIDs as container

identifier, while the lower 16 bit 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-veth-extra=</option></term>

<listitem><para>Adds an additional virtual Ethernet link

between host and container. Takes a colon-separated pair of

host interface name and container interface name. The latter

may be omitted in which case the container and host sides will

be assigned the same name. This switch is independent of

<option>--network-veth</option>, and -- in contrast -- may be

used multiple times, and allows configuration of the network

interface names. Note that <option>--network-bridge=</option>

has no effect on interfaces created with

<option>--network-veth-extra=</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 with

<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, which 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 a 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

a <literal>tmpfs</literal> instance into it (the system thus

starts up with read-only OS resources and configuration, but

pristine state, and 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

of being 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=23 --installroot=/srv/mycontainer --disablerepo='*' --enablerepo=fedora --enablerepo=updates 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>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>