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| Copyright 2010 Lennart Poettering |
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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> |