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/>.
-->
<refmeta>
<refentrytitle>systemd</refentrytitle>
- <manvolnum>8</manvolnum>
+ <manvolnum>1</manvolnum>
</refmeta>
<refnamediv>
<refname>systemd</refname>
- <refpurpose>systemd System and Session Manager</refpurpose>
+ <refname>init</refname>
+ <refpurpose>systemd System and Service Manager</refpurpose>
</refnamediv>
+ <refsynopsisdiv>
+ <cmdsynopsis>
+ <command>systemd <arg choice="opt" rep="repeat">OPTIONS</arg></command>
+ </cmdsynopsis>
+ <cmdsynopsis>
+ <command>init <arg choice="opt" rep="repeat">OPTIONS</arg> <arg choice="req">COMMAND</arg></command>
+ </cmdsynopsis>
+ </refsynopsisdiv>
+
<refsect1>
<title>Description</title>
- <para>Systemd is awesome.</para>
+ <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>
+
+ <para>For compatibility with SysV, if systemd is called
+ as <command>init</command> and a PID that is not
+ 1, it will execute <command>telinit</command> and pass
+ all command line arguments unmodified. That means
+ <command>init</command> and <command>telinit</command>
+ 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.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>
+ for more information.</para>
+ </refsect1>
+
+ <refsect1>
+ <title>Options</title>
+
+ <para>The following options are understood:</para>
+
+ <variablelist>
+ <varlistentry>
+ <term><option>-h</option></term>
+ <term><option>--help</option></term>
+
+ <listitem><para>Prints a short help
+ text and exits.</para></listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><option>--test</option></term>
+
+ <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>--introspect=</option></term>
+
+ <listitem><para>Extract D-Bus
+ interface introspection data. This is
+ mostly useful 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>
+ </varlistentry>
+ <varlistentry>
+ <term><option>--unit=</option></term>
+
+ <listitem><para>Set default unit to
+ activate on startup. If not specified
+ defaults to
+ <filename>default.target</filename>.</para></listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><option>--system</option></term>
+ <term><option>--user</option></term>
+
+ <listitem><para>Tell systemd to run a
+ system instance (resp. user
+ instance), even if the process ID is
+ not 1 (resp. is 1), i.e. systemd is
+ not (resp. is) run as init process.
+ 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>--dump-core</option></term>
+
+ <listitem><para>Dump core on
+ crash. This switch has no effect when
+ run as user
+ instance.</para></listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><option>--crash-shell</option></term>
+
+ <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. 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>--log-target=</option></term>
+
+ <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>
+
+ <listitem><para>Set log level. As
+ argument this accepts a numerical log
+ level or the well-known <citerefentry><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+ symbolic names (lowercase):
+ <option>emerg</option>,
+ <option>alert</option>,
+ <option>crit</option>,
+ <option>err</option>,
+ <option>warning</option>,
+ <option>notice</option>,
+ <option>info</option>,
+ <option>debug</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
+ defaults to
+ <option>true</option>.</para></listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><option>--log-location=</option></term>
+
+ <listitem><para>Include code location
+ in log messages. This is mostly
+ relevant for debugging
+ purposes. Argument is a boolean
+ value. If the argument is omitted
+ 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 resp. error output for all
+ services and sockets, i.e. controls
+ the default for
+ <option>StandardOutput=</option>
+ resp. <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>
+ </variablelist>
+ </refsect1>
+
+ <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 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, 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 (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
+ daemons and the processes they consist of. For
+ details see
+ <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem>
+
+ <listitem><para>Socket units, which
+ encapsulate local IPC or network sockets in
+ the system, useful for socket-based
+ activation. For details about socket units see
+ <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
+ for details on socket-based activation and
+ other forms of activation, see
+ <citerefentry><refentrytitle>daemon</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para></listitem>
+
+ <listitem><para>Target units are useful to
+ group units, or provide well-known
+ synchronization points during boot-up, see
+ <citerefentry><refentrytitle>systemd.target</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem>
+
+ <listitem><para>Device units expose kernel
+ devices in systemd and may be used to
+ implement device-based activation. For details
+ see
+ <citerefentry><refentrytitle>systemd.device</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem>
+
+ <listitem><para>Mount units control mount
+ points in the file system, for details see
+ <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem>
+
+ <listitem><para>Automount units provide
+ automount capabilities, for on-demand mounting
+ of file systems as well as parallelized
+ boot-up. See
+ <citerefentry><refentrytitle>systemd.automount</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem>
+
+ <listitem><para>Snapshot units can be used to
+ temporarily save the state of the set of
+ systemd units, which later may be restored by
+ activating the saved snapshot unit. For more
+ information see
+ <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
+ timers. You may find details in
+ <citerefentry><refentrytitle>systemd.timer</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem>
+
+ <listitem><para>Swap units are very similar to
+ mount units and encapsulate memory swap
+ partitions or files of the operating
+ system. They are described in <citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem>
+
+ <listitem><para>Path units may be used
+ to activate other services when file system
+ objects change or are modified. See
+ <citerefentry><refentrytitle>systemd.path</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem>
+
+ </orderedlist>
+
+ <para>Units are named as their configuration
+ files. Some units have special semantics. A detailed
+ 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 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>graphical.target</filename> (for
+ fully-featured boots into the UI) or
+ <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
+ 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="http://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 host name 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
+ url="http://0pointer.de/blog/projects/systemd.html">Original
+ 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>
+ </refsect1>
+
+ <refsect1>
+ <title>Directories</title>
+
+ <variablelist>
+ <varlistentry>
+ <term>System unit directories</term>
+
+ <listitem><para>The systemd system
+ manager reads unit configuration from
+ various directories. Packages that
+ want to install unit files shall place
+ them in the directory returned by
+ <command>pkg-config systemd
+ --variable=systemdsystemunitdir</command>. Other
+ directories checked are
+ <filename>/usr/local/lib/systemd/system</filename>
+ and
+ <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
+ <command>enable</command> and
+ <command>disable</command> commands of
+ the
+ <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
+ tool.</para></listitem>
+ </varlistentry>
+ </variablelist>
+
+ <variablelist>
+ <varlistentry>
+ <term>User unit directories</term>
+
+ <listitem><para>Similar rules apply
+ 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>
+ is followed to find
+ units. Applications should place their
+ unit files in the directory returned
+ by <command>pkg-config systemd
+ --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>
+ </varlistentry>
+ </variablelist>
+
+ <variablelist>
+ <varlistentry>
+ <term>SysV init scripts directory</term>
+
+ <listitem><para>The location of the
+ SysV init script directory varies
+ between distributions. If systemd
+ cannot find a native unit file for a
+ requested service, it will look for a
+ SysV init script of the same name
+ (with the
+ <filename>.service</filename> suffix
+ removed).</para></listitem>
+ </varlistentry>
+ </variablelist>
+
+ <variablelist>
+ <varlistentry>
+ <term>SysV runlevel link farm directory</term>
+
+ <listitem><para>The location of the
+ SysV runlevel link farm directory
+ varies between distributions. systemd
+ will take the link farm into account
+ when figuring out whether a service
+ shall be enabled. Note that a service
+ unit with a native unit configuration
+ file cannot be started by activating it
+ in the SysV runlevel link
+ farm.</para></listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
+
+ <refsect1>
+ <title>Signals</title>
+
+ <variablelist>
+ <varlistentry>
+ <term>SIGTERM</term>
+
+ <listitem><para>Upon receiving this
+ signal the systemd system manager
+ serializes its state, reexecutes
+ itself and deserializes the saved
+ state again. This is mostly equivalent
+ to <command>systemctl
+ daemon-reexec</command>.</para>
+
+ <para>systemd user managers will
+ start the
+ <filename>exit.target</filename> unit
+ when this signal is received. This is
+ mostly equivalent to
+ <command>systemctl --user start
+ exit.target</command>.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>SIGINT</term>
+
+ <listitem><para>Upon receiving this
+ signal the systemd system manager will
+ start the
+ <filename>ctrl-alt-del.target</filename> unit. This
+ is mostly equivalent to
+ <command>systemctl start
+ ctl-alt-del.target</command>.</para>
+
+ <para>systemd user managers
+ treat this signal the same way as
+ SIGTERM.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>SIGWINCH</term>
+
+ <listitem><para>When this signal is
+ received the systemd system manager
+ will start the
+ <filename>kbrequest.target</filename>
+ unit. This is mostly equivalent to
+ <command>systemctl start
+ kbrequest.target</command>.</para>
+
+ <para>This signal is ignored by
+ systemd user
+ managers.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>SIGPWR</term>
+
+ <listitem><para>When this signal is
+ received the systemd manager
+ will start the
+ <filename>sigpwr.target</filename>
+ unit. This is mostly equivalent to
+ <command>systemctl start
+ sigpwr.target</command>.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>SIGUSR1</term>
+
+ <listitem><para>When this signal is
+ received the systemd manager will try
+ to reconnect to the D-Bus
+ bus.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>SIGUSR2</term>
+
+ <listitem><para>When this signal is
+ received the systemd manager will log
+ its complete state in human readable
+ form. The data logged is the same as
+ printed by <command>systemctl
+ dump</command>.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>SIGHUP</term>
+
+ <listitem><para>Reloads the complete
+ daemon configuration. This is mostly
+ equivalent to <command>systemctl
+ daemon-reload</command>.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>SIGRTMIN+0</term>
+
+ <listitem><para>Enters default mode, starts the
+ <filename>default.target</filename>
+ unit. This is mostly equivalent to
+ <command>systemctl start
+ default.target</command>.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>SIGRTMIN+1</term>
+
+ <listitem><para>Enters rescue mode,
+ starts the
+ <filename>rescue.target</filename>
+ unit. This is mostly equivalent to
+ <command>systemctl isolate
+ rescue.target</command>.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>SIGRTMIN+2</term>
+
+ <listitem><para>Enters emergency mode,
+ starts the
+ <filename>emergency.service</filename>
+ unit. This is mostly equivalent to
+ <command>systemctl isolate
+ emergency.service</command>.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>SIGRTMIN+3</term>
+
+ <listitem><para>Halts the machine,
+ starts the
+ <filename>halt.target</filename>
+ unit. This is mostly equivalent to
+ <command>systemctl start
+ halt.target</command>.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>SIGRTMIN+4</term>
+
+ <listitem><para>Powers off the machine,
+ starts the
+ <filename>poweroff.target</filename>
+ unit. This is mostly equivalent to
+ <command>systemctl start
+ poweroff.target</command>.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>SIGRTMIN+5</term>
+
+ <listitem><para>Reboots the machine,
+ starts the
+ <filename>reboot.target</filename>
+ unit. This is mostly equivalent to
+ <command>systemctl start
+ reboot.target</command>.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>SIGRTMIN+6</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>SIGRTMIN+13</term>
+
+ <listitem><para>Immediately halts the machine.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>SIGRTMIN+14</term>
+
+ <listitem><para>Immediately powers off the machine.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>SIGRTMIN+15</term>
+
+ <listitem><para>Immediately reboots the machine.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>SIGRTMIN+16</term>
+
+ <listitem><para>Immediately reboots the machine with kexec.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>SIGRTMIN+20</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>SIGRTMIN+21</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>SIGRTMIN+22</term>
+ <term>SIGRTMIN+23</term>
+
+ <listitem><para>Sets the log level to
+ <literal>debug</literal>
+ (resp. <literal>info</literal> on
+ <literal>SIGRTMIN+23</literal>), as
+ controlled via
+ <varname>systemd.log_level=debug</varname>
+ (resp. <varname>systemd.log_level=info</varname>
+ on <literal>SIGRTMIN+23</literal>) on
+ the kernel command
+ line.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>SIGRTMIN+26</term>
+ <term>SIGRTMIN+27</term>
+ <term>SIGRTMIN+28</term>
+ <term>SIGRTMIN+29</term>
+
+ <listitem><para>Sets the log level to
+ <literal>journal-or-kmsg</literal>
+ (resp. <literal>console</literal> on
+ <literal>SIGRTMIN+27</literal>;
+ resp. <literal>kmsg</literal> on
+ <literal>SIGRTMIN+28</literal>;
+ resp. <literal>syslog-or-kmsg</literal>
+ on <literal>SIGRTMIN+29</literal>), as
+ controlled via
+ <varname>systemd.log_target=journal-or-kmsg</varname>
+ (resp. <varname>systemd.log_target=console</varname>
+ on <literal>SIGRTMIN+27</literal>;
+ resp. <varname>systemd.log_target=kmsg</varname>
+ on <literal>SIGRTMIN+28</literal>;
+ resp
+ <varname>systemd.log_target=syslog-or-kmsg</varname>
+ on <literal>SIGRTMIN+29</literal>) on
+ the kernel command
+ line.</para></listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
+
+ <refsect1>
+ <title>Environment</title>
+
+ <variablelist>
+ <varlistentry>
+ <term><varname>$SYSTEMD_LOG_LEVEL</varname></term>
+ <listitem><para>systemd reads the
+ log level from this environment
+ variable. This can be overridden with
+ <option>--log-level=</option>.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>$SYSTEMD_LOG_TARGET</varname></term>
+ <listitem><para>systemd reads the
+ log target from this environment
+ variable. This can be overridden with
+ <option>--log-target=</option>.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>$SYSTEMD_LOG_COLOR</varname></term>
+ <listitem><para>Controls whether
+ systemd highlights important log
+ messages. This can be overridden with
+ <option>--log-color=</option>.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>$SYSTEMD_LOG_LOCATION</varname></term>
+ <listitem><para>Controls whether
+ systemd prints the code location along
+ with log messages. This can be
+ overridden with
+ <option>--log-location=</option>.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>$XDG_CONFIG_HOME</varname></term>
+ <term><varname>$XDG_CONFIG_DIRS</varname></term>
+ <term><varname>$XDG_DATA_HOME</varname></term>
+ <term><varname>$XDG_DATA_DIRS</varname></term>
+
+ <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
+ Base Directory specification</ulink>
+ to find its configuration.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>$SYSTEMD_UNIT_PATH</varname></term>
+
+ <listitem><para>Controls where systemd
+ looks for unit
+ files.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>$SYSTEMD_SYSVINIT_PATH</varname></term>
+
+ <listitem><para>Controls where systemd
+ looks for SysV init scripts.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>$SYSTEMD_SYSVRCND_PATH</varname></term>
+
+ <listitem><para>Controls where systemd
+ looks for SysV init script runlevel link
+ farms.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>$LISTEN_PID</varname></term>
+ <term><varname>$LISTEN_FDS</varname></term>
+
+ <listitem><para>Set by systemd for
+ supervised processes during
+ socket-based activation. See
+ <citerefentry><refentrytitle>sd_listen_fds</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+ for more information.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>$NOTIFY_SOCKET</varname></term>
+
+ <listitem><para>Set by systemd for
+ supervised processes for status and
+ start-up completion notification. See
+ <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+ for more information.
+ </para></listitem>
+ </varlistentry>
+ </variablelist>
</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>
+ <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 honoured
+ only in the initial RAM disk (initrd),
+ while the one that isn't 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
+ <literal>-1</literal>.</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. If <option>true</option>
+ shows terse service status updates on
+ the console during bootup. Defaults to
+ <option>true</option>, unless
+ <option>quiet</option> is passed as
+ kernel command line option in which
+ case it defaults to
+ <option>false</option>.</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/error output for
+ services, with the same effect as the
+ <option>--default-standard-output=</option>
+ resp. <option>--default-standard-error=</option>
+ command line arguments described
+ above.</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
+ environment variables for the init
+ process and all its children at boot
+ time. May be used more than once to
+ set multiple variables. If the equal
+ sign and variable are missing unsets
+ an environment variable which might be
+ passed in from the initial ram
+ disk.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>quiet</varname></term>
+
+ <listitem><para>If passed turns 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 to the
+ kernel. Passing this option hence
+ turns off the usual output from both
+ the system manager and the
+ kernel.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <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. This
+ is equivalent to
+ <varname>systemd.unit=runlevel2.target</varname>,
+ <varname>systemd.unit=runlevel3.target</varname>,
+ <varname>systemd.unit=runlevel4.target</varname>,
+ resp. <varname>systemd.unit=runlevel5.target</varname>
+ 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>/run/systemd/notify</filename></term>
+
+ <listitem><para>Daemon status
+ notification socket. This is an
+ AF_UNIX 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>/run/systemd/shutdownd</filename></term>
+
+ <listitem><para>Used internally by the
+ <citerefentry><refentrytitle>shutdown</refentrytitle><manvolnum>8</manvolnum></citerefentry>
+ tool to implement delayed
+ shutdowns. This is an AF_UNIX datagram
+ socket.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <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. This interface
+ is private to systemd and should not
+ be used in external
+ projects.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><filename>/dev/initctl</filename></term>
+
+ <listitem><para>Limited compatibility
+ support for the SysV client interface,
+ as implemented by the
+ <filename>systemd-initctl.service</filename>
+ unit. This is a named pipe in the file
+ system. This interface is obsolete and
+ should not be used in new
+ applications.</para></listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
<refsect1>
<title>See Also</title>
<para>
+ <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>systemadm</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>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>kernel-command-line</refentrytitle><manvolnum>7</manvolnum></citerefentry>
</para>
</refsect1>
~ianmdlvl / elogind.git / blobdiff