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-<refentry id="systemd">
-
- <refentryinfo>
- <title>systemd</title>
- <productname>systemd</productname>
-
- <authorgroup>
- <author>
- <contrib>Developer</contrib>
- <firstname>Lennart</firstname>
- <surname>Poettering</surname>
- <email>lennart@poettering.net</email>
- </author>
- </authorgroup>
- </refentryinfo>
-
- <refmeta>
- <refentrytitle>systemd</refentrytitle>
- <manvolnum>1</manvolnum>
- </refmeta>
-
- <refnamediv>
- <refname>systemd</refname>
- <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 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-system.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>--version</option></term>
-
- <listitem><para>Prints a systemd version
- identifier 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>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>--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 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>
- </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 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
- 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>
-
- <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>
- <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. Full list of directories is provided in
- <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
- </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. Full list of directories is provided in
- <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
- </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><constant>SIGTERM</constant></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><constant>SIGINT</constant></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><constant>SIGWINCH</constant></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><constant>SIGPWR</constant></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><constant>SIGUSR1</constant></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><constant>SIGUSR2</constant></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><constant>SIGHUP</constant></term>
-
- <listitem><para>Reloads the complete
- daemon configuration. This is mostly
- equivalent to <command>systemctl
- daemon-reload</command>.</para></listitem>
- </varlistentry>
-
- <varlistentry>
- <term><constant>SIGRTMIN+0</constant></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><constant>SIGRTMIN+1</constant></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><constant>SIGRTMIN+2</constant></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><constant>SIGRTMIN+3</constant></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><constant>SIGRTMIN+4</constant></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><constant>SIGRTMIN+5</constant></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><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 class='environment-variables'>
- <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 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 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
- <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. 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 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
- 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 it 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>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>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>/run/systemd/notify</filename></term>
-
- <listitem><para>Daemon status
- 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>/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 <constant>AF_UNIX</constant> 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
- <constant>AF_UNIX</constant> 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>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>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>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>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>
+<refentry id="systemd"
+ xmlns:xi="http://www.w3.org/2001/XInclude">
+
+ <refentryinfo>
+ <title>systemd</title>
+ <productname>systemd</productname>
+
+ <authorgroup>
+ <author>
+ <contrib>Developer</contrib>
+ <firstname>Lennart</firstname>
+ <surname>Poettering</surname>
+ <email>lennart@poettering.net</email>
+ </author>
+ </authorgroup>
+ </refentryinfo>
+
+ <refmeta>
+ <refentrytitle>systemd</refentrytitle>
+ <manvolnum>1</manvolnum>
+ </refmeta>
+
+ <refnamediv>
+ <refname>systemd</refname>
+ <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 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 a system instance, systemd interprets the
+ configuration file <filename>system.conf</filename> and the files
+ in <filename>system.conf.d</filename> directories; when run as a
+ user instance, systemd interprets the configuration file
+ <filename>user.conf</filename> and the files in
+ <filename>user.conf.d</filename> directories. See
+ <citerefentry><refentrytitle>systemd-system.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>--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>--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>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>--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>kmsg</option>,
+ <option>journal-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 project='man-pages'><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 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>
+
+ <refsect1>
+ <title>Concepts</title>
+
+ <para>systemd provides a dependency system between 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,
+ 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 (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 start and 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>
+
+ <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 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="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 project='man-pages'><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 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>
+
+ <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>
+ <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. Full list of directories is provided in
+ <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
+ </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. Full list of
+ directories is provided in
+ <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
+ </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><constant>SIGTERM</constant></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><constant>SIGINT</constant></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>. If this signal is received more
+ often than 7 times per 2s an immediate reboot is triggered.
+ Note that pressing Ctrl-Alt-Del on the console will trigger
+ this signal. Hence, if a reboot is hanging pressing
+ Ctrl-Alt-Del more than 7 times in 2s is a relatively safe way
+ to trigger an immediate reboot.</para>
+
+ <para>systemd user managers treat this signal the same way as
+ <constant>SIGTERM</constant>.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><constant>SIGWINCH</constant></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><constant>SIGPWR</constant></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><constant>SIGUSR1</constant></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><constant>SIGUSR2</constant></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>systemd-analyze dump</command>.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><constant>SIGHUP</constant></term>
+
+ <listitem><para>Reloads the complete daemon configuration.
+ This is mostly equivalent to <command>systemctl
+ daemon-reload</command>.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><constant>SIGRTMIN+0</constant></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><constant>SIGRTMIN+1</constant></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><constant>SIGRTMIN+2</constant></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><constant>SIGRTMIN+3</constant></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><constant>SIGRTMIN+4</constant></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><constant>SIGRTMIN+5</constant></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><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>
+
+ <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>), as controlled via
+ <varname>systemd.log_target=journal-or-kmsg</varname> (or
+ <varname>systemd.log_target=console</varname> on
+ <constant>SIGRTMIN+27</constant> or
+ <varname>systemd.log_target=kmsg</varname> on
+ <constant>SIGRTMIN+28</constant>) on the kernel command
+ line.</para></listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
+
+ <refsect1>
+ <title>Environment</title>
+
+ <variablelist class='environment-variables'>
+ <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 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>emergency</varname></term>
+ <term><varname>-b</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>rescue</varname></term>
+ <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>/run/systemd/notify</filename></term>
+
+ <listitem><para>Daemon status 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>/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
+ <constant>AF_UNIX</constant> 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
+ <constant>AF_UNIX</constant> 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>
+ 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>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>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
+ <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>kernel-command-line</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
+ <citerefentry project='man-pages'><refentrytitle>bootup</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>
+ </para>
+ </refsect1>
</refentry>
~ianmdlvl / elogind.git / blobdiff