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Diffstat (limited to 'man/systemd-nspawn.xml')
| -rw-r--r-- | man/systemd-nspawn.xml | 166 |
1 files changed, 101 insertions, 65 deletions
diff --git a/man/systemd-nspawn.xml b/man/systemd-nspawn.xml index 476cc2932f..69d2f6ff7d 100644 --- a/man/systemd-nspawn.xml +++ b/man/systemd-nspawn.xml @@ -67,69 +67,80 @@ <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 + <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> may be invoked on any directory tree containing an operating system tree, + using the <option>--directory=</option> command line option. By using the <option>--machine=</option> option an OS + tree is automatically searched for in a couple of locations, most importantly in + <filename>/var/lib/machines</filename>, the suggested directory to place container images installed on the + system.</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><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>. The + host's 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>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 + <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. See + the Examples section below for details on suitable invocation of these commands.</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> + + <para><command>systemd-nspawn</command> may be invoked directly from the interactive command line or run as system + service in the background. In this mode each container instance runs as its own service instance; a default + template unit file <filename>systemd-nspawn@.service</filename> is provided to make this easy, taking the container + name as instance identifier. Note that different default options apply when <command>systemd-nspawn</command> is + invoked by the template unit file than interactively on the command line. Most importantly the template unit file + makes use of the <option>--boot</option> which is not the default in case <command>systemd-nspawn</command> is + invoked from the interactive command line. Further differences with the defaults are documented along with the + various supported options below.</para> + + <para>The <citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry> tool may + be used to execute a number of operations on containers. In particular it provides easy-to-use commands to run + containers as system services using the <filename>systemd-nspawn@.service</filename> template unit + file.</para> + + <para>Along with each container a settings file with the <filename>.nspawn</filename> suffix may exist, containing + additional settings to apply when running the container. See + <citerefentry><refentrytitle>systemd.nspawn</refentrytitle><manvolnum>5</manvolnum></citerefentry> for + details. Settings files override the default options used by the <filename>systemd-nspawn@.service</filename> + template unit file, making it usually unnecessary to alter this template file directly.</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> or <command>shell</command> commands to request an additional login session 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>While running, containers invoked with <command>systemd-nspawn</command> are registered with the + <citerefentry><refentrytitle>systemd-machined</refentrytitle><manvolnum>8</manvolnum></citerefentry> service that + keeps track of running containers, and provides programming interfaces to interact with them.</para> </refsect1> <refsect1> @@ -139,7 +150,7 @@ 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 + arguments for this program. If <option>--boot</option> is not used and no arguments are specified, a shell is launched in the container.</para> @@ -310,6 +321,9 @@ </tbody> </tgroup> </table> + + <para>Note that <option>--boot</option> is the default mode of operation if the + <filename>systemd-nspawn@.service</filename> template unit file is used.</para> </listitem> </varlistentry> @@ -446,7 +460,10 @@ <listitem><para>If the kernel supports the user namespaces feature, equivalent to <option>--private-users=pick</option>, otherwise equivalent to - <option>--private-users=no</option>.</para></listitem> + <option>--private-users=no</option>.</para> + + <para>Note that <option>-U</option> is the default if the <filename>systemd-nspawn@.service</filename> template unit + file is used.</para></listitem> </varlistentry> <varlistentry> @@ -540,6 +557,9 @@ assignment via DHCP. In case <filename>systemd-networkd</filename> is running on both the host and inside the container, automatic IP communication from the container to the host is thus available, with further connectivity to the external network.</para> + + <para>Note that <option>--network-veth</option> is the default if the + <filename>systemd-nspawn@.service</filename> template unit file is used.</para> </listitem> </varlistentry> @@ -705,7 +725,10 @@ 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> + <literal>auto</literal> is used.</para> + + <para>Note that <option>--link-journal=try-guest</option> is the default if the + <filename>systemd-nspawn@.service</filename> template unit file is used.</para></listitem> </varlistentry> <varlistentry> @@ -910,8 +933,8 @@ <literal>tmpfs</literal> instance, and <filename>/usr</filename> from the OS tree is mounted into it in read-only mode (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 + image, but pristine state and configuration, any changes + 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 @@ -980,6 +1003,19 @@ effect.</para></listitem> </varlistentry> + <varlistentry> + <term><option>--notify-ready=</option></term> + + <listitem><para>Configures support for notifications from the container's init process. + <option>--notify-ready=</option> takes a boolean (<option>no</option> and <option>yes</option>). + With option <option>no</option> systemd-nspawn notifies systemd + with a <literal>READY=1</literal> message when the init process is created. + With option <option>yes</option> systemd-nspawn waits for the + <literal>READY=1</literal> message from the init process in the container + before sending its own to systemd. For more details about notifications + see <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>).</para></listitem> + </varlistentry> + <xi:include href="standard-options.xml" xpointer="help" /> <xi:include href="standard-options.xml" xpointer="version" /> </variablelist> |