chiark / gitweb /
man: ipv4 link-local
[elogind.git] / man / systemd.xml
index 007705e..331e6c2 100644 (file)
@@ -8,20 +8,21 @@
   Copyright 2010 Lennart Poettering
 
   systemd is free software; you can redistribute it and/or modify it
-  under the terms of the GNU General Public License as published by
-  the Free Software Foundation; either version 2 of the License, or
+  under the terms of the GNU Lesser General Public License as published by
+  the Free Software Foundation; either version 2.1 of the License, or
   (at your option) any later version.
 
   systemd is distributed in the hope that it will be useful, but
   WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
-  General Public License for more details.
+  Lesser General Public License for more details.
 
-  You should have received a copy of the GNU General Public License
+  You should have received a copy of the GNU Lesser General Public License
   along with systemd; If not, see <http://www.gnu.org/licenses/>.
 -->
 
-<refentry id="systemd">
+<refentry id="systemd"
+          xmlns:xi="http://www.w3.org/2001/XInclude">
 
         <refentryinfo>
                 <title>systemd</title>
@@ -45,7 +46,7 @@
         <refnamediv>
                 <refname>systemd</refname>
                 <refname>init</refname>
-                <refpurpose>systemd System and Session Manager</refpurpose>
+                <refpurpose>systemd system and service manager</refpurpose>
         </refnamediv>
 
         <refsynopsisdiv>
@@ -60,7 +61,7 @@
         <refsect1>
                 <title>Description</title>
 
-                <para>systemd is a system and session manager for
+                <para>systemd is a system and service manager for
                 Linux operating systems. When run as first process on
                 boot (as PID 1), it acts as init system that brings
                 up and maintains userspace services.</para>
                 are mostly equivalent when invoked from normal login sessions. See
                 <citerefentry><refentrytitle>telinit</refentrytitle><manvolnum>8</manvolnum></citerefentry>
                 for more information.</para>
+
+                <para>When run as system instance, systemd interprets
+                the configuration file
+                <filename>system.conf</filename>, otherwise
+                <filename>user.conf</filename>. See
+                <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>
+                for more information.</para>
         </refsect1>
 
         <refsect1>
 
                 <variablelist>
                         <varlistentry>
-                                <term><option>-h</option></term>
-                                <term><option>--help</option></term>
+                                <term><option>--test</option></term>
 
-                                <listitem><para>Prints a short help
-                                text and exits.</para></listitem>
+                                <listitem><para>Determine startup
+                                sequence, dump it and exit. This is an
+                                option useful for debugging
+                                only.</para></listitem>
+                        </varlistentry>
+                        <varlistentry>
+                                <term><option>--dump-configuration-items</option></term>
+
+                                <listitem><para>Dump understood unit
+                                configuration items. This outputs a
+                                terse but complete list of
+                                configuration items understood in unit
+                                definition files.</para></listitem>
                         </varlistentry>
                         <varlistentry>
                                 <term><option>--unit=</option></term>
 
                                 <listitem><para>Set default unit to
-                                activate on startup. If not specified
+                                activate on startup. If not specified,
                                 defaults to
                                 <filename>default.target</filename>.</para></listitem>
                         </varlistentry>
                         <varlistentry>
-                                <term><option>--running-as=</option></term>
-
-                                <listitem><para>Tell systemd to run in
-                                a particular mode. Argument is one of
-                                <option>system</option>,
-                                <option>session</option>. Normally it
-                                should not be necessary to pass this
-                                option, as systemd automatically
-                                detects the mode it is started
-                                in. This call is hence of little use
-                                except for
-                                debugging.</para></listitem>
+                                <term><option>--system</option></term>
+                                <term><option>--user</option></term>
+
+                                <listitem><para>For <option>--system</option>,
+                                tell systemd to run a
+                                system instance, even if the process ID is
+                                not 1, i.e. systemd is not run as init process.
+                                <option>--user</option> does the opposite,
+                                running a user instance even if the process
+                                ID is 1.
+                                Normally it should not be necessary to
+                                pass these options, as systemd
+                                automatically detects the mode it is
+                                started in. These options are hence of
+                                little use except for debugging. Note
+                                that it is not supported booting and
+                                maintaining a full system with systemd
+                                running in <option>--system</option>
+                                mode, but PID not 1. In practice,
+                                passing <option>--system</option> explicitly is
+                                only useful in conjunction with
+                                <option>--test</option>.</para></listitem>
                         </varlistentry>
                         <varlistentry>
-                                <term><option>--test</option></term>
+                                <term><option>--dump-core</option></term>
 
-                                <listitem><para>Determine startup
-                                sequence, dump it and exit. This is an
-                                option useful for debugging
-                                only.</para></listitem>
+                                <listitem><para>Dump core on
+                                crash. This switch has no effect when
+                                run as user
+                                instance.</para></listitem>
                         </varlistentry>
                         <varlistentry>
-                                <term><option>--dump-configuration-items</option></term>
+                                <term><option>--crash-shell</option></term>
 
-                                <listitem><para>Dump understood unit
-                                configuration items. This outputs a
-                                terse but complete list of
-                                configuration items understood in unit
-                                definition files.</para></listitem>
+                                <listitem><para>Run shell on
+                                crash. This switch has no effect when
+                                run as user
+                                instance.</para></listitem>
                         </varlistentry>
                         <varlistentry>
                                 <term><option>--confirm-spawn</option></term>
 
-                                <listitem><para>Ask for confirmation when spawning processes.</para></listitem>
+                                <listitem><para>Ask for confirmation
+                                when spawning processes. This switch
+                                has no effect when run as user
+                                instance.</para></listitem>
+                        </varlistentry>
+                        <varlistentry>
+                                <term><option>--show-status=</option></term>
+
+                                <listitem><para>Show terse service
+                                status information while booting. This
+                                switch has no effect when run as user
+                                instance. Takes a boolean argument
+                                which may be omitted which is
+                                interpreted as
+                                <option>true</option>.</para></listitem>
                         </varlistentry>
                         <varlistentry>
-                                <term><option>--introspect=</option></term>
+                                <term><option>--log-target=</option></term>
 
-                                <listitem><para>Extract D-Bus
-                                interface introspection data. This is
-                                mostly useful at build at install time
-                                to generate data suitable for the
-                                D-Bus interfaces
-                                repository. Optionally the interface
-                                name for the introspection data may be
-                                specified. If omitted, the
-                                introspection data for all interfaces
-                                is dumped.</para></listitem>
+                                <listitem><para>Set log
+                                target. Argument must be one of
+                                <option>console</option>,
+                                <option>journal</option>,
+                                <option>syslog</option>,
+                                <option>kmsg</option>,
+                                <option>journal-or-kmsg</option>,
+                                <option>syslog-or-kmsg</option>,
+                                <option>null</option>.</para></listitem>
                         </varlistentry>
                         <varlistentry>
                                 <term><option>--log-level=</option></term>
                                 <option>debug</option>.</para></listitem>
                         </varlistentry>
                         <varlistentry>
-                                <term><option>--log-target=</option></term>
-
-                                <listitem><para>Set log
-                                target. Argument must be one of
-                                <option>console</option>,
-                                <option>syslog</option>,
-                                <option>kmsg</option>,
-                                <option>syslog-or-kmsg</option>,
-                                <option>null</option>.</para></listitem>
-                        </varlistentry>
-                        <varlistentry>
                                 <term><option>--log-color=</option></term>
 
                                 <listitem><para>Highlight important
                                 log messages. Argument is a boolean
-                                value. If the argument is omitted it
+                                value. If the argument is omitted, it
                                 defaults to
                                 <option>true</option>.</para></listitem>
                         </varlistentry>
                                 it defaults to
                                 <option>true</option>.</para></listitem>
                         </varlistentry>
+                        <varlistentry>
+                                <term><option>--default-standard-output=</option></term>
+                                <term><option>--default-standard-error=</option></term>
+
+                                <listitem><para>Sets the default
+                                output or error output for all
+                                services and sockets, respectively. That is, controls
+                                the default for
+                                <option>StandardOutput=</option>
+                                and <option>StandardError=</option>
+                                (see
+                                <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>
+                                for details). Takes one of
+                                <option>inherit</option>,
+                                <option>null</option>,
+                                <option>tty</option>,
+                                <option>journal</option>,
+                                <option>journal+console</option>,
+                                <option>syslog</option>,
+                                <option>syslog+console</option>,
+                                <option>kmsg</option>,
+                                <option>kmsg+console</option>.  If the
+                                argument is omitted
+                                <option>--default-standard-output=</option>
+                                defaults to <option>journal</option>
+                                and
+                                <option>--default-standard-error=</option>
+                                to
+                                <option>inherit</option>.</para></listitem>
+                        </varlistentry>
+
+                        <xi:include href="standard-options.xml" xpointer="help" />
+                        <xi:include href="standard-options.xml" xpointer="version" />
                 </variablelist>
         </refsect1>
 
                 <title>Concepts</title>
 
                 <para>systemd provides a dependency system between
-                various entities called "units". Units encapsulate
-                various objects that are relevant for system boot-up
-                and maintainance. The majority of units are configured
-                in unit configuration files, whose syntax and basic
-                set of options is described in
+                various entities called "units" of 12 different
+                types. Units encapsulate various objects that are
+                relevant for system boot-up and maintenance. The
+                majority of units are configured in unit configuration
+                files, whose syntax and basic set of options is
+                described in
                 <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
                 however some are created automatically from other
-                configuration or dynamically from system state. Units
-                may be active (meaning started, bound, plugged in, ...
-                depending on the unit type), or inactive (meaning
-                stopped, unbound, unplugged, ...), as well is in the
+                configuration, dynamically from system state or
+                programmatically at runtime. Units may be "active"
+                (meaning started, bound, plugged in, ..., depending on
+                the unit type, see below), or "inactive" (meaning
+                stopped, unbound, unplugged, ...), as well as in the
                 process of being activated or deactivated,
-                i.e. between the two states. The following unit types
-                are available:</para>
+                i.e. between the two states (these states are called
+                "activating", "deactivating"). A special "failed"
+                state is available as well, which is very similar to
+                "inactive" and is entered when the service failed in
+                some way (process returned error code on exit, or
+                crashed, or an operation timed out). If this state is
+                entered, the cause will be logged, for later
+                reference. Note that the various unit types may have a
+                number of additional substates, which are mapped to
+                the five generalized unit states described
+                here.</para>
+
+                <para>The following unit types are available:</para>
 
                 <orderedlist>
-                        <listitem><para>Service units, which control
+                        <listitem><para>Service units, which start and control
                         daemons and the processes they consist of. For
                         details see
                         <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem>
                         systemd units, which later may be restored by
                         activating the saved snapshot unit. For more
                         information see
-                        <citerefentry><refentrytitle>systemd.automount</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem>
+                        <citerefentry><refentrytitle>systemd.snapshot</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem>
 
                         <listitem><para>Timer units are useful for
                         triggering activation of other units based on
                         <citerefentry><refentrytitle>systemd.timer</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem>
 
                         <listitem><para>Swap units are very similar to
-                        mount units and encapsulated memory swap
+                        mount units and encapsulate memory swap
                         partitions or files of the operating
-                        systemd. They are described in <citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem>
+                        system. They are described in <citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem>
 
                         <listitem><para>Path units may be used
-                        activate other services when file system
+                        to activate other services when file system
                         objects change or are modified. See
                         <citerefentry><refentrytitle>systemd.path</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem>
 
+                        <listitem><para>Slice units may be used to
+                        group units which manage system processes
+                        (such as service and scope units) in a
+                        hierarchical tree for resource management
+                        purposes. See
+                        <citerefentry><refentrytitle>systemd.slice</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem>
+
+                        <listitem><para>Scope units are similar to
+                        service units, but manage foreign processes
+                        instead of starting them as well. See
+                        <citerefentry><refentrytitle>systemd.scope</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem>
+
                 </orderedlist>
 
                 <para>Units are named as their configuration
                 files. Some units have special semantics. A detailed
-                list you may find in
+                list is available in
                 <citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para>
 
+                <para>systemd knows various kinds of dependencies,
+                including positive and negative requirement
+                dependencies (i.e. <varname>Requires=</varname> and
+                <varname>Conflicts=</varname>) as well as ordering
+                dependencies (<varname>After=</varname> and
+                <varname>Before=</varname>). NB: ordering and
+                requirement dependencies are orthogonal. If only a
+                requirement dependency exists between two units
+                (e.g. <filename>foo.service</filename> requires
+                <filename>bar.service</filename>), but no ordering
+                dependency (e.g. <filename>foo.service</filename>
+                after <filename>bar.service</filename>) and both are
+                requested to start, they will be started in
+                parallel. It is a common pattern that both requirement
+                and ordering dependencies are placed between two
+                units. Also note that the majority of dependencies are
+                implicitly created and maintained by systemd. In most
+                cases, it should be unnecessary to declare additional
+                dependencies manually, however it is possible to do
+                this.</para>
+
+                <para>Application programs and units (via
+                dependencies) may request state changes of units. In
+                systemd, these requests are encapsulated as 'jobs' and
+                maintained in a job queue. Jobs may succeed or can
+                fail, their execution is ordered based on the ordering
+                dependencies of the units they have been scheduled
+                for.</para>
+
                 <para>On boot systemd activates the target unit
-                <filename>default.target</filename> whose job it is to
+                <filename>default.target</filename> whose job is to
                 activate on-boot services and other on-boot units by
                 pulling them in via dependencies. Usually the unit
                 name is just an alias (symlink) for either
                 <filename>multi-user.target</filename> (for limited
                 console-only boots for use in embedded or server
                 environments, or similar; a subset of
-                graphical.target). However it is at the discretion of
+                graphical.target). However, it is at the discretion of
                 the administrator to configure it as an alias to any
                 other target unit. See
                 <citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry>
                 for details about these target units.</para>
 
+                <para>Processes systemd spawns are placed in
+                individual Linux control groups named after the unit
+                which they belong to in the private systemd
+                hierarchy. (see <ulink
+                url="https://www.kernel.org/doc/Documentation/cgroups/cgroups.txt">cgroups.txt</ulink>
+                for more information about control groups, or short
+                "cgroups"). systemd uses this to effectively keep
+                track of processes. Control group information is
+                maintained in the kernel, and is accessible via the
+                file system hierarchy (beneath
+                <filename>/sys/fs/cgroup/systemd/</filename>), or in tools
+                such as
+                <citerefentry><refentrytitle>ps</refentrytitle><manvolnum>1</manvolnum></citerefentry>
+                (<command>ps xawf -eo pid,user,cgroup,args</command>
+                is particularly useful to list all processes and the
+                systemd units they belong to.).</para>
+
+                <para>systemd is compatible with the SysV init system
+                to a large degree: SysV init scripts are supported and
+                simply read as an alternative (though limited)
+                configuration file format. The SysV
+                <filename>/dev/initctl</filename> interface is
+                provided, and compatibility implementations of the
+                various SysV client tools are available. In addition to
+                that, various established Unix functionality such as
+                <filename>/etc/fstab</filename> or the
+                <filename>utmp</filename> database are
+                supported.</para>
+
+                <para>systemd has a minimal transaction system: if a
+                unit is requested to start up or shut down it will add
+                it and all its dependencies to a temporary
+                transaction. Then, it will verify if the transaction
+                is consistent (i.e. whether the ordering of all units
+                is cycle-free). If it is not, systemd will try to fix
+                it up, and removes non-essential jobs from the
+                transaction that might remove the loop. Also, systemd
+                tries to suppress non-essential jobs in the
+                transaction that would stop a running service. Finally
+                it is checked whether the jobs of the transaction
+                contradict jobs that have already been queued, and
+                optionally the transaction is aborted then. If all
+                worked out and the transaction is consistent and
+                minimized in its impact it is merged with all already
+                outstanding jobs and added to the run
+                queue. Effectively this means that before executing a
+                requested operation, systemd will verify that it makes
+                sense, fixing it if possible, and only failing if it
+                really cannot work.</para>
+
+                <para>Systemd contains native implementations of
+                various tasks that need to be executed as part of the
+                boot process. For example, it sets the hostname or
+                configures the loopback network device. It also sets
+                up and mounts various API file systems, such as
+                <filename>/sys</filename> or
+                <filename>/proc</filename>.</para>
+
                 <para>For more information about the concepts and
-                ideas behind systemd please refer to the <ulink
+                ideas behind systemd, please refer to the <ulink
                 url="http://0pointer.de/blog/projects/systemd.html">Original
-                Announcement Document</ulink>.</para>
+                Design Document</ulink>.</para>
+
+                <para>Note that some but not all interfaces provided
+                by systemd are covered by the <ulink
+                url="http://www.freedesktop.org/wiki/Software/systemd/InterfaceStabilityPromise">Interface
+                Stability Promise</ulink>.</para>
+
+                <para>Units may be generated dynamically at boot and
+                system manager reload time, for example based on other
+                configuration files or parameters passed on the kernel
+                command line. For details see the <ulink
+                url="http://www.freedesktop.org/wiki/Software/systemd/Generators">Generators
+                Specification</ulink>.</para>
+
+                <para>Systems which invoke systemd in a container
+                or initrd environment should implement the
+                <ulink
+                url="http://www.freedesktop.org/wiki/Software/systemd/ContainerInterface">Container
+                Interface</ulink> or <ulink
+                url="http://www.freedesktop.org/wiki/Software/systemd/InitrdInterface">initrd
+                Interface</ulink> specifications, respectively.</para>
         </refsect1>
 
         <refsect1>
                                 <command>pkg-config systemd
                                 --variable=systemdsystemunitdir</command>. Other
                                 directories checked are
-                                <filename>/usr/local/share/systemd/system</filename>
+                                <filename>/usr/local/lib/systemd/system</filename>
                                 and
-                                <filename>/usr/share/systemd/system</filename>. User
+                                <filename>/usr/lib/systemd/system</filename>. User
                                 configuration always takes
                                 precedence. <command>pkg-config
                                 systemd
                                 --variable=systemdsystemconfdir</command>
                                 returns the path of the system
                                 configuration directory. Packages
-                                should alter the content of these directories
-                                only with the
-                                <citerefentry><refentrytitle>systemd-install</refentrytitle><manvolnum>1</manvolnum></citerefentry>
-                                tool.</para></listitem>
+                                should alter the content of these
+                                directories only with the
+                                <command>enable</command> and
+                                <command>disable</command> commands of
+                                the
+                                <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
+                                tool. Full list of directories is provided in
+                                <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
+                                </para></listitem>
                         </varlistentry>
                 </variablelist>
 
                 <variablelist>
                         <varlistentry>
-                                <term>Session unit directories</term>
+                                <term>User unit directories</term>
 
                                 <listitem><para>Similar rules apply
-                                for the session unit
+                                for the user unit
                                 directories. However, here the <ulink
                                 url="http://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html">XDG
                                 Base Directory specification</ulink>
                                 units. Applications should place their
                                 unit files in the directory returned
                                 by <command>pkg-config systemd
-                                --variable=systemdsessionunitdir</command>. Global
-                                configuration is done in the
-                                directory reported by
-                                <command>pkg-config systemd
-                                --variable=systemdsessionconfdir</command>. The
-                                <citerefentry><refentrytitle>systemd-install</refentrytitle><manvolnum>1</manvolnum></citerefentry>
+                                --variable=systemduserunitdir</command>. Global
+                                configuration is done in the directory
+                                reported by <command>pkg-config
+                                systemd
+                                --variable=systemduserconfdir</command>. The
+                                <command>enable</command> and
+                                <command>disable</command> commands of
+                                the
+                                <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
                                 tool can handle both global (i.e. for
                                 all users) and private (for one user)
                                 enabling/disabling of
-                                units.</para></listitem>
+                                units. Full list of directories is provided in
+                                <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
+                                </para></listitem>
                         </varlistentry>
                 </variablelist>
 
                                 when figuring out whether a service
                                 shall be enabled. Note that a service
                                 unit with a native unit configuration
-                                file can be started by activating it
+                                file cannot be started by activating it
                                 in the SysV runlevel link
                                 farm.</para></listitem>
                         </varlistentry>
 
                 <variablelist>
                         <varlistentry>
-                                <term>SIGTERM</term>
+                                <term><constant>SIGTERM</constant></term>
 
                                 <listitem><para>Upon receiving this
                                 signal the systemd system manager
                                 to <command>systemctl
                                 daemon-reexec</command>.</para>
 
-                                <para>systemd session managers will
+                                <para>systemd user managers will
                                 start the
                                 <filename>exit.target</filename> unit
                                 when this signal is received. This is
                                 mostly equivalent to
-                                <command>systemctl --session start
+                                <command>systemctl --user start
                                 exit.target</command>.</para></listitem>
                         </varlistentry>
 
                         <varlistentry>
-                                <term>SIGINT</term>
+                                <term><constant>SIGINT</constant></term>
 
                                 <listitem><para>Upon receiving this
                                 signal the systemd system manager will
                                 <command>systemctl start
                                 ctl-alt-del.target</command>.</para>
 
-                                <para>systemd session managers
+                                <para>systemd user managers
                                 treat this signal the same way as
-                                SIGTERM.</para></listitem>
+                                <constant>SIGTERM</constant>.</para></listitem>
                         </varlistentry>
 
                         <varlistentry>
-                                <term>SIGWINCH</term>
+                                <term><constant>SIGWINCH</constant></term>
 
                                 <listitem><para>When this signal is
                                 received the systemd system manager
                                 kbrequest.target</command>.</para>
 
                                 <para>This signal is ignored by
-                                systemd session
+                                systemd user
                                 managers.</para></listitem>
                         </varlistentry>
 
                         <varlistentry>
-                                <term>SIGPWR</term>
+                                <term><constant>SIGPWR</constant></term>
 
                                 <listitem><para>When this signal is
                                 received the systemd manager
                         </varlistentry>
 
                         <varlistentry>
-                                <term>SIGUSR1</term>
+                                <term><constant>SIGUSR1</constant></term>
 
                                 <listitem><para>When this signal is
                                 received the systemd manager will try
                         </varlistentry>
 
                         <varlistentry>
-                                <term>SIGUSR2</term>
+                                <term><constant>SIGUSR2</constant></term>
 
                                 <listitem><para>When this signal is
                                 received the systemd manager will log
                         </varlistentry>
 
                         <varlistentry>
-                                <term>SIGHUP</term>
+                                <term><constant>SIGHUP</constant></term>
 
                                 <listitem><para>Reloads the complete
                                 daemon configuration. This is mostly
                         </varlistentry>
 
                         <varlistentry>
-                                <term>SIGRTMIN+0</term>
+                                <term><constant>SIGRTMIN+0</constant></term>
 
                                 <listitem><para>Enters default mode, starts the
                                 <filename>default.target</filename>
                         </varlistentry>
 
                         <varlistentry>
-                                <term>SIGRTMIN+1</term>
+                                <term><constant>SIGRTMIN+1</constant></term>
 
                                 <listitem><para>Enters rescue mode,
                                 starts the
                         </varlistentry>
 
                         <varlistentry>
-                                <term>SIGRTMIN+2</term>
+                                <term><constant>SIGRTMIN+2</constant></term>
 
                                 <listitem><para>Enters emergency mode,
                                 starts the
                         </varlistentry>
 
                         <varlistentry>
-                                <term>SIGRTMIN+3</term>
+                                <term><constant>SIGRTMIN+3</constant></term>
 
                                 <listitem><para>Halts the machine,
                                 starts the
                         </varlistentry>
 
                         <varlistentry>
-                                <term>SIGRTMIN+4</term>
+                                <term><constant>SIGRTMIN+4</constant></term>
 
                                 <listitem><para>Powers off the machine,
                                 starts the
                         </varlistentry>
 
                         <varlistentry>
-                                <term>SIGRTMIN+5</term>
+                                <term><constant>SIGRTMIN+5</constant></term>
 
                                 <listitem><para>Reboots the machine,
                                 starts the
                                 <command>systemctl start
                                 reboot.target</command>.</para></listitem>
                         </varlistentry>
+
+                        <varlistentry>
+                                <term><constant>SIGRTMIN+6</constant></term>
+
+                                <listitem><para>Reboots the machine via kexec,
+                                starts the
+                                <filename>kexec.target</filename>
+                                unit. This is mostly equivalent to
+                                <command>systemctl start
+                                kexec.target</command>.</para></listitem>
+                        </varlistentry>
+
+                        <varlistentry>
+                                <term><constant>SIGRTMIN+13</constant></term>
+
+                                <listitem><para>Immediately halts the machine.</para></listitem>
+                        </varlistentry>
+
+                        <varlistentry>
+                                <term><constant>SIGRTMIN+14</constant></term>
+
+                                <listitem><para>Immediately powers off the machine.</para></listitem>
+                        </varlistentry>
+
+                        <varlistentry>
+                                <term><constant>SIGRTMIN+15</constant></term>
+
+                                <listitem><para>Immediately reboots the machine.</para></listitem>
+                        </varlistentry>
+
+                        <varlistentry>
+                                <term><constant>SIGRTMIN+16</constant></term>
+
+                                <listitem><para>Immediately reboots the machine with kexec.</para></listitem>
+                        </varlistentry>
+
+                        <varlistentry>
+                                <term><constant>SIGRTMIN+20</constant></term>
+
+                                <listitem><para>Enables display of
+                                status messages on the console, as
+                                controlled via
+                                <varname>systemd.show_status=1</varname>
+                                on the kernel command
+                                line.</para></listitem>
+                        </varlistentry>
+
+                        <varlistentry>
+                                <term><constant>SIGRTMIN+21</constant></term>
+
+                                <listitem><para>Disables display of
+                                status messages on the console, as
+                                controlled via
+                                <varname>systemd.show_status=0</varname>
+                                on the kernel command
+                                line.</para></listitem>
+                        </varlistentry>
+
+                        <varlistentry>
+                                <term><constant>SIGRTMIN+22</constant></term>
+                                <term><constant>SIGRTMIN+23</constant></term>
+
+                                <listitem><para>Sets the log level to
+                                <literal>debug</literal>
+                                (or <literal>info</literal> on
+                                <constant>SIGRTMIN+23</constant>), as
+                                controlled via
+                                <varname>systemd.log_level=debug</varname>
+                                (or <varname>systemd.log_level=info</varname>
+                                on <constant>SIGRTMIN+23</constant>) on
+                                the kernel command
+                                line.</para></listitem>
+                        </varlistentry>
+
+                        <varlistentry>
+                                <term><constant>SIGRTMIN+24</constant></term>
+
+                                <listitem><para>Immediately exits the
+                                manager (only available for --user
+                                instances).</para></listitem>
+                        </varlistentry>
+
+                        <varlistentry>
+                                <term><constant>SIGRTMIN+26</constant></term>
+                                <term><constant>SIGRTMIN+27</constant></term>
+                                <term><constant>SIGRTMIN+28</constant></term>
+                                <term><constant>SIGRTMIN+29</constant></term>
+
+                                <listitem><para>Sets the log level to
+                                <literal>journal-or-kmsg</literal>
+                                (or <literal>console</literal> on
+                                <constant>SIGRTMIN+27</constant>,
+                                <literal>kmsg</literal> on
+                                <constant>SIGRTMIN+28</constant>,
+                                or <literal>syslog-or-kmsg</literal>
+                                on <constant>SIGRTMIN+29</constant>), as
+                                controlled via
+                                <varname>systemd.log_target=journal-or-kmsg</varname>
+                                (or <varname>systemd.log_target=console</varname>
+                                on <constant>SIGRTMIN+27</constant>,
+                                <varname>systemd.log_target=kmsg</varname>
+                                on <constant>SIGRTMIN+28</constant>,
+                                or
+                                <varname>systemd.log_target=syslog-or-kmsg</varname>
+                                on <constant>SIGRTMIN+29</constant>) on
+                                the kernel command
+                                line.</para></listitem>
+                        </varlistentry>
                 </variablelist>
         </refsect1>
 
         <refsect1>
                 <title>Environment</title>
 
-                <variablelist>
+                <variablelist class='environment-variables'>
                         <varlistentry>
                                 <term><varname>$SYSTEMD_LOG_LEVEL</varname></term>
                                 <listitem><para>systemd reads the
                                 <term><varname>$XDG_DATA_HOME</varname></term>
                                 <term><varname>$XDG_DATA_DIRS</varname></term>
 
-                                <listitem><para>The systemd session
+                                <listitem><para>The systemd user
                                 manager uses these variables in
                                 accordance to the <ulink
                                 url="http://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html">XDG
         </refsect1>
 
         <refsect1>
+                <title>Kernel Command Line</title>
+
+                <para>When run as system instance systemd parses a
+                number of kernel command line
+                arguments<footnote><para>If run inside a Linux
+                container these arguments may be passed as command
+                line arguments to systemd itself, next to any of the
+                command line options listed in the Options section
+                above. If run outside of Linux containers, these
+                arguments are parsed from
+                <filename>/proc/cmdline</filename>
+                instead.</para></footnote>:</para>
+
+                <variablelist class='kernel-commandline-options'>
+                        <varlistentry>
+                                <term><varname>systemd.unit=</varname></term>
+                                <term><varname>rd.systemd.unit=</varname></term>
+
+                                <listitem><para>Overrides the unit to
+                                activate on boot. Defaults to
+                                <filename>default.target</filename>. This
+                                may be used to temporarily boot into a
+                                different boot unit, for example
+                                <filename>rescue.target</filename> or
+                                <filename>emergency.service</filename>. See
+                                <citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry>
+                                for details about these units. The
+                                option prefixed with
+                                <literal>rd.</literal> is honored
+                                only in the initial RAM disk (initrd),
+                                while the one that is not prefixed only
+                                in the main system.</para></listitem>
+                        </varlistentry>
+
+                        <varlistentry>
+                                <term><varname>systemd.dump_core=</varname></term>
+
+                                <listitem><para>Takes a boolean
+                                argument. If <option>true</option>,
+                                systemd dumps core when it
+                                crashes. Otherwise, no core dump is
+                                created. Defaults to
+                                <option>true</option>.</para></listitem>
+                        </varlistentry>
+
+                        <varlistentry>
+                                <term><varname>systemd.crash_shell=</varname></term>
+
+                                <listitem><para>Takes a boolean
+                                argument. If <option>true</option>,
+                                systemd spawns a shell when it
+                                crashes. Otherwise, no shell is
+                                spawned. Defaults to
+                                <option>false</option>, for security
+                                reasons, as the shell is not protected
+                                by any password
+                                authentication.</para></listitem>
+                        </varlistentry>
+
+                        <varlistentry>
+                                <term><varname>systemd.crash_chvt=</varname></term>
+
+                                <listitem><para>Takes an integer
+                                argument. If positive systemd
+                                activates the specified virtual
+                                terminal when it crashes. Defaults to
+                                <constant>-1</constant>.</para></listitem>
+                        </varlistentry>
+
+                        <varlistentry>
+                                <term><varname>systemd.confirm_spawn=</varname></term>
+
+                                <listitem><para>Takes a boolean
+                                argument. If <option>true</option>,
+                                asks for confirmation when spawning
+                                processes. Defaults to
+                                <option>false</option>.</para></listitem>
+                        </varlistentry>
+
+                        <varlistentry>
+                                <term><varname>systemd.show_status=</varname></term>
+
+                                <listitem><para>Takes a boolean
+                                argument or the constant
+                                <constant>auto</constant>. If
+                                <option>true</option>, shows terse
+                                service status updates on the console
+                                during bootup.
+                                <constant>auto</constant> behaves like
+                                <option>false</option> until a service
+                                fails or there is a significant delay
+                                in boot. Defaults to
+                                <option>true</option>, unless
+                                <option>quiet</option> is passed as
+                                kernel command line option in which
+                                case it defaults to
+                                <constant>auto</constant>.</para></listitem>
+                        </varlistentry>
+
+                        <varlistentry>
+                                <term><varname>systemd.log_target=</varname></term>
+                                <term><varname>systemd.log_level=</varname></term>
+                                <term><varname>systemd.log_color=</varname></term>
+                                <term><varname>systemd.log_location=</varname></term>
+
+                                <listitem><para>Controls log output,
+                                with the same effect as the
+                                <varname>$SYSTEMD_LOG_TARGET</varname>, <varname>$SYSTEMD_LOG_LEVEL</varname>, <varname>$SYSTEMD_LOG_COLOR</varname>, <varname>$SYSTEMD_LOG_LOCATION</varname>
+                                environment variables described above.</para></listitem>
+                        </varlistentry>
+
+                        <varlistentry>
+                                <term><varname>systemd.default_standard_output=</varname></term>
+                                <term><varname>systemd.default_standard_error=</varname></term>
+                                <listitem><para>Controls default
+                                standard output and error output for
+                                services, with the same effect as the
+                                <option>--default-standard-output=</option>
+                                and <option>--default-standard-error=</option>
+                                command line arguments described
+                                above, respectively.</para></listitem>
+                        </varlistentry>
+
+                        <varlistentry>
+                                <term><varname>systemd.setenv=</varname></term>
+
+                                <listitem><para>Takes a string
+                                argument in the form VARIABLE=VALUE.
+                                May be used to set default environment
+                                variables to add to forked child processes.
+                                May be used more than once to set multiple
+                                variables.</para></listitem>
+                        </varlistentry>
+
+                        <varlistentry>
+                                <term><varname>quiet</varname></term>
+
+                                <listitem><para>Turn off
+                                status output at boot, much like
+                                <varname>systemd.show_status=false</varname>
+                                would. Note that this option is also
+                                read by the kernel itself and disables
+                                kernel log output. Passing this option
+                                hence turns off the usual output from
+                                both the system manager and the kernel.
+                                </para></listitem>
+                        </varlistentry>
+
+                        <varlistentry>
+                                <term><varname>debug</varname></term>
+
+                                <listitem><para>Turn on debugging
+                                output. This is equivalent to
+                                <varname>systemd.log_level=debug</varname>.
+                                Note that this option is also read by
+                                the kernel itself and enables kernel
+                                debug output.  Passing this option
+                                hence turns on the debug output from
+                                both the system manager and the
+                                kernel.</para></listitem>
+                        </varlistentry>
+
+                        <varlistentry>
+                                <term><varname>-b</varname></term>
+                                <term><varname>emergency</varname></term>
+
+                                <listitem><para>Boot into emergency
+                                mode. This is equivalent to
+                                <varname>systemd.unit=emergency.target</varname>
+                                and provided for compatibility
+                                reasons and to be easier to type.</para></listitem>
+                        </varlistentry>
+
+                        <varlistentry>
+                                <term><varname>single</varname></term>
+                                <term><varname>s</varname></term>
+                                <term><varname>S</varname></term>
+                                <term><varname>1</varname></term>
+
+                                <listitem><para>Boot into rescue
+                                mode. This is equivalent to
+                                <varname>systemd.unit=rescue.target</varname>
+                                and provided for compatibility reasons
+                                and to be easier to
+                                type.</para></listitem>
+                        </varlistentry>
+
+                        <varlistentry>
+                                <term><varname>2</varname></term>
+                                <term><varname>3</varname></term>
+                                <term><varname>4</varname></term>
+                                <term><varname>5</varname></term>
+
+                                <listitem><para>Boot into the
+                                specified legacy SysV runlevel. These
+                                are equivalent to
+                                <varname>systemd.unit=runlevel2.target</varname>,
+                                <varname>systemd.unit=runlevel3.target</varname>,
+                                <varname>systemd.unit=runlevel4.target</varname>,
+                                and <varname>systemd.unit=runlevel5.target</varname>, respectively,
+                                and provided for compatibility reasons
+                                and to be easier to
+                                type.</para></listitem>
+                        </varlistentry>
+
+                        <varlistentry>
+                                <term><varname>locale.LANG=</varname></term>
+                                <term><varname>locale.LANGUAGE=</varname></term>
+                                <term><varname>locale.LC_CTYPE=</varname></term>
+                                <term><varname>locale.LC_NUMERIC=</varname></term>
+                                <term><varname>locale.LC_TIME=</varname></term>
+                                <term><varname>locale.LC_COLLATE=</varname></term>
+                                <term><varname>locale.LC_MONETARY=</varname></term>
+                                <term><varname>locale.LC_MESSAGES=</varname></term>
+                                <term><varname>locale.LC_PAPER=</varname></term>
+                                <term><varname>locale.LC_NAME=</varname></term>
+                                <term><varname>locale.LC_ADDRESS=</varname></term>
+                                <term><varname>locale.LC_TELEPHONE=</varname></term>
+                                <term><varname>locale.LC_MEASUREMENT=</varname></term>
+                                <term><varname>locale.LC_IDENTIFICATION=</varname></term>
+
+                                <listitem><para>Set the system locale
+                                to use. This overrides the settings in
+                                <filename>/etc/locale.conf</filename>. For
+                                more information see
+                                <citerefentry><refentrytitle>locale.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>
+                                and
+                                <citerefentry><refentrytitle>locale</refentrytitle><manvolnum>7</manvolnum></citerefentry>.
+                                </para></listitem>
+                        </varlistentry>
+                </variablelist>
+
+                <para>For other kernel command line parameters
+                understood by components of the core OS, please refer
+                to
+                <citerefentry><refentrytitle>kernel-command-line</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para>
+        </refsect1>
+
+        <refsect1>
                 <title>Sockets and FIFOs</title>
 
                 <variablelist>
                         <varlistentry>
-                                <term><filename>@/org/freedesktop/systemd1/notify</filename></term>
+                                <term><filename>/run/systemd/notify</filename></term>
 
                                 <listitem><para>Daemon status
-                                notification socket. This is an AF_UNIX
-                                datagram socket in the Linux abstract
-                                namespace, and is used to implement
-                                the daemon notification logic as
-                                implemented by
+                                notification socket. This is an
+                                <constant>AF_UNIX</constant> datagram socket and is used to
+                                implement the daemon notification
+                                logic as implemented by
                                 <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para></listitem>
 
                         </varlistentry>
 
                         <varlistentry>
-                                <term><filename>@/org/freedesktop/systemd1/logger</filename></term>
+                                <term><filename>/run/systemd/shutdownd</filename></term>
 
                                 <listitem><para>Used internally by the
-                                <filename>systemd-logger.service</filename>
-                                unit to connect STDOUT and/or STDERR
-                                of spawned processes to
-                                <citerefentry><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>
-                                or the kernel log buffer. This is an
-                                AF_UNIX stream socket in the Linux
-                                abstract namespace.</para></listitem>
+                                <citerefentry><refentrytitle>shutdown</refentrytitle><manvolnum>8</manvolnum></citerefentry>
+                                tool to implement delayed
+                                shutdowns. This is an <constant>AF_UNIX</constant> datagram
+                                socket.</para></listitem>
                         </varlistentry>
 
                         <varlistentry>
-                                <term><filename>@/org/freedesktop/systemd1/private</filename></term>
+                                <term><filename>/run/systemd/private</filename></term>
 
                                 <listitem><para>Used internally as
                                 communication channel between
                                 <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
                                 and the systemd process. This is an
-                                AF_UNIX stream socket in the Linux
-                                abstract namespace. This interface is
-                                private to systemd and should not be
-                                used in external
+                                <constant>AF_UNIX</constant> stream socket. This interface
+                                is private to systemd and should not
+                                be used in external
                                 projects.</para></listitem>
                         </varlistentry>
 
         <refsect1>
                 <title>See Also</title>
                 <para>
+                        The <ulink url="http://www.freedesktop.org/wiki/Software/systemd/">systemd Homepage</ulink>,
+                        <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
+                        <citerefentry><refentrytitle>locale.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
                         <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
-                        <citerefentry><refentrytitle>systemadm</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
-                        <citerefentry><refentrytitle>systemd-install</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
+                        <citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
                         <citerefentry><refentrytitle>systemd-notify</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
                         <citerefentry><refentrytitle>daemon</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
-                        <citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
+                        <citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
                         <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
                         <citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
-                        <citerefentry><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
+                        <citerefentry><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
+                        <citerefentry><refentrytitle>kernel-command-line</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
+                        <citerefentry><refentrytitle>bootup</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
+                        <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>
                 </para>
         </refsect1>