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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 Session 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 session 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>

</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>--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>--running-as=</option></term>

<listitem><para>Tell systemd to run in

a particular mode. Argument is one of

<option>system</option>,

<option>session</option>. Normally it

should not be necessary to pass this

option, as systemd automatically

detects the mode it is started

in. This call is hence of little use

except for

debugging.</para></listitem>

</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>--confirm-spawn</option></term>

<listitem><para>Ask for confirmation when spawning processes.</para></listitem>

</varlistentry>

<varlistentry>

<term><option>--introspect=</option></term>

<listitem><para>Extract D-Bus

interface introspection data. This is

mostly useful at build at install time

to generate data suitable for the

D-Bus interfaces

repository. Optionally the interface

name for the introspection data may be

specified. If omitted, the

introspection data for all interfaces

is dumped.</para></listitem>

</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-target=</option></term>

<listitem><para>Set log

target. Argument must be one of

<option>console</option>,

<option>syslog</option>,

<option>kmsg</option>,

<option>syslog-or-kmsg</option>,

<option>null</option>.</para></listitem>

</varlistentry>

<varlistentry>

<term><option>--log-color=</option></term>

<listitem><para>Highlight important

log messages. Argument is a boolean

value. If the argument is omitted it

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>

</variablelist>

</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/share/systemd/system</filename>

and

<filename>/usr/share/systemd/system</filename>. User

configuration always takes

precedence. <command>pkg-config

systemd

--variable=systemdsystemconfdir</command>

returns the path of the system

configuration directory. Packages

should alter the content of these directories

only with the

<citerefentry><refentrytitle>systemd-install</refentrytitle><manvolnum>1</manvolnum></citerefentry>

tool.</para></listitem>

</varlistentry>

</variablelist>

<variablelist>

<varlistentry>

<term>Session unit directories</term>

<listitem><para>Similar rules apply

for the session 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=systemdsessionunitdir</command>. Global

configuration is done in the

directory reported by

<command>pkg-config systemd

--variable=systemdsessionconfdir</command>. The

<citerefentry><refentrytitle>systemd-install</refentrytitle><manvolnum>1</manvolnum></citerefentry>

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 can 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 session managers will

start the

<filename>exit.target</filename> unit

when this signal is received. This is

mostly equivalent to

<command>systemctl --session 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 session 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 session

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>

</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 session

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>Sockets and FIFOs</title>

<variablelist>

<varlistentry>

<term><filename>@/org/freedesktop/systemd1/notify</filename></term>

<listitem><para>Daemon status

notification socket. This is an AF_UNIX

datagram socket in the Linux abstract

namespace, and is used to implement

the daemon notification logic as

implemented by

<citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para></listitem>

</varlistentry>

<varlistentry>

<term><filename>@/org/freedesktop/systemd1/logger</filename></term>

<listitem><para>Used internally by the

<filename>systemd-logger.service</filename>

unit to connect STDOUT and/or STDERR

of spawned processes to

<citerefentry><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>

or the kernel log buffer. This is an

AF_UNIX stream socket in the Linux

abstract namespace.</para></listitem>

</varlistentry>

<varlistentry>

<term><filename>@/org/freedesktop/systemd1/private</filename></term>

<listitem><para>Used internally as

communication channel between

<citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>

and the systemd process. This is an

AF_UNIX stream socket in the Linux

abstract namespace. This interface is

private to systemd and should not be

used in external

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-install</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>

</para>

</refsect1>

</refentry>