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![Zbigniew Jędrzejewski-Szmek](/assets/img/avatar_default.png)
The version info added directly to --capsule. If we add the same switch in other places in the future, we will have to move this. Closes https://github.com/systemd/systemd/issues/33048.
123 lines
6.7 KiB
XML
123 lines
6.7 KiB
XML
<?xml version="1.0"?>
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
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<refentry id="capsule_.service"
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xmlns:xi="http://www.w3.org/2001/XInclude">
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<refentryinfo>
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<title>capsule@.service</title>
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<productname>systemd</productname>
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</refentryinfo>
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<refmeta>
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<refentrytitle>capsule@.service</refentrytitle>
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<manvolnum>5</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>capsule@.service</refname>
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<refpurpose>System unit for the capsule service manager</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<para><filename>capsule@<replaceable>NAME</replaceable>.service</filename></para>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para>Service managers for capsules run in
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<filename>capsule@<replaceable>NAME</replaceable>.service</filename> system units, with the capsule name as the
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instance identifier. Capsules are way to run additional instances of the service manager, under dynamic
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user IDs, i.e. UIDs that are allocated when the capsule service manager is started, and released when it
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is stopped.</para>
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<para>In many ways <filename>capsule@.service</filename> is similar to the per-user
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<filename>user@.service</filename> service manager, but there are a few important distinctions:</para>
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<itemizedlist>
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<listitem><para>The capsule service manager utilizes <varname>DynamicUser=</varname> (see
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<citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>) to
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allocate a new UID dynamically on invocation. The user name is automatically generated from the capsule
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name, by prefixng <literal>p_</literal>. The UID is released when the service is terminated. The user
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service manager on the other hand operates under a statically allocated user ID that must be
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pre-existing, before the user service manager is invoked.</para></listitem>
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<listitem><para>User service managers register themselves with <citerefentry
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project='man-pages'><refentrytitle>pam</refentrytitle><manvolnum>8</manvolnum></citerefentry>, capsule
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service managers do not.</para></listitem>
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<listitem><para>User service managers typically read their configuration from a
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<varname>$HOME</varname> directory below <filename>/home/</filename>, capsule service managers from a
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<varname>$HOME</varname> directory below <filename>/var/lib/capsules/</filename>.</para></listitem>
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<listitem><para>User service managers are collectively contained in the <filename>user.slice</filename>
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unit, capsule service managers in <filename>capsule.slice</filename>. Also see
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<citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para></listitem>
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<listitem><para>User service managers start the user unit <filename>default.target</filename>
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initially. Capsule service managers invoke the user unit <filename>capsule@.target</filename>
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instead.</para></listitem>
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</itemizedlist>
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<para>The capsule service manager and the capsule's bus broker can be reached via the
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<option>--capsule=</option> switch to
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<citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd-run</refentrytitle><manvolnum>1</manvolnum></citerefentry> and
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<citerefentry><refentrytitle>busctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>.</para>
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<para>New capsules can be started via a simple <command>systemctl start
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capsule@<replaceable>NAME</replaceable>.service</command> command, and stopped via <command>systemctl
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stop capsule@<replaceable>NAME</replaceable>.service</command>. Starting a capsule will implicitly create
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a home directory <filename>/var/lib/capsules/<replaceable>NAME</replaceable>/</filename>, if missing. A
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runtime directory is created as <filename>/run/capsules/<replaceable>NAME</replaceable>/</filename>. To
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remove these resources use <command>systemctl clean capsule@<replaceable>NAME</replaceable>.service</command>,
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for example with the <option>--what=all</option> switch.</para>
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<para>The <filename>capsule@.service</filename> unit invokes a <command>systemd --user</command>
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service manager process. This means unit files are looked for according to the sames rules as for regular user
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service managers, for example in
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<filename>/var/lib/capsules/<replaceable>NAME</replaceable>/.config/systemd/user/</filename>.</para>
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<para>Capsule names may be chosen freely by the user, however, they must be suitable as UNIX filenames
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(i.e. 255 characters max, and contain no <literal>/</literal>), and when prefixed with
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<literal>p-</literal> be suitable as a user name matching strict POSIX rules, see <ulink
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url="https://systemd.io/USER_NAMES">User/Group Name Syntax</ulink> for details.</para>
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<xi:include href="version-info.xml" xpointer="v256"/>
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</refsect1>
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<refsect1>
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<title>Examples</title>
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<example>
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<title>Create a new capsule, invoke two programs in it (one interactively), terminate it, and clean everything up</title>
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<programlisting># systemctl start capsule@tatze.service
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# systemd-run --capsule=tatze --unit=sleeptest.service sleep 999
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# systemctl --capsule=tatze status sleeptest.service
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# systemd-run -t --capsule=tatze bash
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# systemctl --capsule=tatze stop sleeptest.service
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# systemctl stop capsule@tatze.service
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# systemctl clean --all capsule@tatze.service</programlisting>
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</example>
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</refsect1>
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<refsect1>
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<title>See Also</title>
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<para>
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<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>user@.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd.slice</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd-run</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>busctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry project='man-pages'><refentrytitle>pam</refentrytitle><manvolnum>8</manvolnum></citerefentry>
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</para>
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</refsect1>
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</refentry>
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