<?xml version='1.0'?> <!--*-nxml-*--> <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> <!-- This file is part of systemd. Copyright 2010 Lennart Poettering systemd is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. systemd is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with systemd; If not, see <http://www.gnu.org/licenses/>. --> <refentry id="systemd.special"> <refentryinfo> <title>systemd.special</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.special</refentrytitle> <manvolnum>7</manvolnum> </refmeta> <refnamediv> <refname>systemd.special</refname> <refpurpose>special systemd units</refpurpose> </refnamediv> <refsynopsisdiv> <para><filename>basic.target</filename>, <filename>ctrl-alt-del.target</filename>, <filename>@SPECIAL_DBUS_SERVICE@</filename>, <filename>default.target</filename>, <filename>display-manager.service</filename>, <filename>emergency.service</filename>, <filename>exit.service</filename>, <filename>graphical.target</filename>, <filename>halt.target</filename>, <filename>kbrequest.target</filename>, <filename>local-fs.target</filename>, <filename>mail-transfer-agent.target</filename>, <filename>multi-user.target</filename>, <filename>network.target</filename>, <filename>nss-lookup.target</filename>, <filename>poweroff.target</filename>, <filename>reboot.target</filename>, <filename>remote-fs.target</filename>, <filename>rescue.target</filename>, <filename>rpcbind.target</filename>, <filename>rtc-set.target</filename>, <filename>runlevel0.target</filename>, <filename>runlevel1.target</filename>, <filename>runlevel2.target</filename>, <filename>runlevel3.target</filename>, <filename>runlevel4.target</filename>, <filename>runlevel5.target</filename>, <filename>runlevel6.target</filename> <filename>shutdown.target</filename>, <filename>sigpwr.target</filename>, <filename>sockets.target</filename>, <filename>swap.target</filename>, <filename>syslog.target</filename>, <filename>@SPECIAL_SYSLOG_SERVICE@</filename>, <filename>systemd-initctl.service</filename>, <filename>systemd-initctl.socket</filename>, <filename>systemd-logger.service</filename>, <filename>systemd-logger.socket</filename></para> </refsynopsisdiv> <refsect1> <title>Description</title> <para>A few units are treated specially by systemd. They have special internal semantics and cannot be renamed.</para> </refsect1> <refsect1> <title>Special System Units</title> <variablelist> <varlistentry> <term><filename>basic.target</filename></term> <listitem> <para>A special target unit covering early boot-up.</para> <para>systemd automatically adds dependencies of the types Requires and After for this target unit to all SysV service units configured for runlevel 1 to 5.</para> <para>systemd automatically adds dependencies of the types Wants and After for all SysV service units configured for runlevels that are not 0 to 6 to this target unit. This covers the special boot-up runlevels some distributions have, such as S or b.</para> </listitem> </varlistentry> <varlistentry> <term><filename>ctrl-alt-del.target</filename></term> <listitem> <para>systemd starts this target whenever Control+Alt+Del is pressed on the console. Usually this should be aliased (symlinked) to <filename>reboot.target</filename>.</para> </listitem> </varlistentry> <varlistentry> <term><filename>@SPECIAL_DBUS_SERVICE@</filename></term> <listitem> <para>A special unit for the D-Bus system bus. As soon as this service is fully started up systemd will connect to it and register its service.</para> </listitem> </varlistentry> <varlistentry> <term><filename>default.target</filename></term> <listitem> <para>The default unit systemd starts at bootup. Usually this should be aliased (symlinked) to <filename>multi-user.target</filename> or <filename>graphical.target</filename>.</para> <para>The default unit systemd starts at bootup can be overriden with the <varname>systemd.default=</varname> kernel command line option.</para> </listitem> </varlistentry> <varlistentry> <term><filename>display-manager.service</filename></term> <listitem> <para>The display manager service. Usually this should be aliased (symlinked) to <filename>gdm.service</filename> or a similar display manager service.</para> <para>systemd automatically adds dependencies of type After for this target unit to all SysV init script service units with an LSB header referring to the <literal>$x-display-manager</literal> facility, for compatibility with Debian.</para> </listitem> </varlistentry> <varlistentry> <term><filename>emergency.service</filename></term> <listitem> <para>A special service unit that starts an emergency shell on the main console. This unit is supposed to be used with the kernel command line option <varname>systemd.default=</varname> and has otherwise little use. </para> </listitem> </varlistentry> <varlistentry> <term><filename>graphical.target</filename></term> <listitem> <para>A special target unit for setting up a graphical login screen. This pulls in <filename>multi-user.target</filename>.</para> <para>Units that are needed for graphical login shall add Wants dependencies for their unit to this unit (or <filename>multi-user.target</filename>) during installation.</para> </listitem> </varlistentry> <varlistentry> <term><filename>halt.target</filename></term> <listitem> <para>A special target unit for shutting down and halting the system.</para> <para>Applications wanting to halt the system should start this unit.</para> </listitem> </varlistentry> <varlistentry> <term><filename>kbrequest.target</filename></term> <listitem> <para>systemd starts this target whenever Alt+ArrowUp is pressed on the console. This is a good candidate to be aliased (symlinked) to <filename>rescue.target</filename>.</para> </listitem> </varlistentry> <varlistentry> <term><filename>local-fs.target</filename></term> <listitem> <para>systemd automatically adds dependencies of type After to all mount units that refer to local mount points for this target unit. In addition, systemd adds dependencies of type Wants to this target unit for those mounts listed in <filename>/etc/fstab</filename> that have the <literal>auto</literal> and <literal>comment=systemd.mount</literal> mount options set.</para> <para>systemd automatically adds dependencies of type After for this target unit to all SysV init script service units with an LSB header referring to the <literal>$local_fs</literal> facility.</para> </listitem> </varlistentry> <varlistentry> <term><filename>mail-transfer-agent.target</filename></term> <listitem> <para>The mail transfer agent (MTA) service. Usually this should pull in all units necessary for sending/receiving mails on the local host.</para> <para>systemd automatically adds dependencies of type After for this target unit to all SysV init script service units with an LSB header referring to the <literal>$mail-transfer-argent</literal> or <literal>$mail-transport-agent</literal> facilities, for compatibility with Debian.</para> </listitem> </varlistentry> <varlistentry> <term><filename>multi-user.target</filename></term> <listitem> <para>A special target unit for setting up a multi-user system (non-graphical). This is pulled in by <filename>graphical.target</filename>.</para> <para>Units that are needed for a multi-user system shall add Wants dependencies to this unit for their unit during installation.</para> </listitem> </varlistentry> <varlistentry> <term><filename>network.target</filename></term> <listitem> <para>systemd automatically adds dependencies of type After for this target unit to all SysV init script service units with an LSB header referring to the <literal>$network</literal> facility.</para> </listitem> </varlistentry> <varlistentry> <term><filename>nss-lookup.target</filename></term> <listitem> <para>systemd automatically adds dependencies of type After for this target unit to all SysV init script service units with an LSB header referring to the <literal>$named</literal> facility.</para> </listitem> </varlistentry> <varlistentry> <term><filename>poweroff.target</filename></term> <listitem> <para>A special target unit for shutting down and powering off the system.</para> <para>Applications wanting to power off the system should start this unit.</para> <para><filename>runlevel0.target</filename> is an alias for this target unit, for compatibility with SysV.</para> </listitem> </varlistentry> <varlistentry> <term><filename>reboot.target</filename></term> <listitem> <para>A special target unit for shutting down and rebooting the system.</para> <para>Applications wanting to reboot the system should start this unit.</para> <para><filename>runlevel6.target</filename> is an alias for this target unit, for compatibility with SysV.</para> </listitem> </varlistentry> <varlistentry> <term><filename>remote-fs.target</filename></term> <listitem> <para>Similar to <filename>local-fs.target</filename>, but for remote mount points.</para> <para>systemd automatically adds dependencies of type After for this target unit to all SysV init script service units with an LSB header referring to the <literal>$remote_fs</literal> facility.</para> </listitem> </varlistentry> <varlistentry> <term><filename>rescue.target</filename></term> <listitem> <para>A special target unit for setting up the base system and a rescue shell.</para> <para><filename>runlevel1.target</filename> is an alias for this target unit, for compatibility with SysV.</para> </listitem> </varlistentry> <varlistentry> <term><filename>rpcbind.target</filename></term> <listitem> <para>systemd automatically adds dependencies of type After for this target unit to all SysV init script service units with an LSB header referring to the <literal>$rpcbind</literal> facility.</para> </listitem> </varlistentry> <varlistentry> <term><filename>rtc-set.target</filename></term> <listitem> <para>systemd automatically adds dependencies of type After for this target unit to all SysV init script service units with an LSB header referring to the <literal>$time</literal> facility.</para> </listitem> </varlistentry> <varlistentry> <term><filename>runlevel0.target</filename></term> <listitem> <para>This is a target that is called whever the SysV compatibility code asks for runlevel 0. This is an alias for <filename>poweroff.target</filename>, for compatibility with SysV.</para> </listitem> </varlistentry> <varlistentry> <term><filename>runlevel1.target</filename></term> <listitem> <para>This is a target that is called whever the SysV compatibility code asks for runlevel 1. This is an alias for <filename>rescue.target</filename>, for compatibility with SysV.</para> </listitem> </varlistentry> <varlistentry> <term><filename>runlevel2.target</filename></term> <listitem> <para>This is a target that is called whever the SysV compatibility code asks for runlevel 2. It is a good idea to make this an alias for (i.e. symlink to) <filename>multi-user.target</filename>.</para> </listitem> </varlistentry> <varlistentry> <term><filename>runlevel3.target</filename></term> <listitem> <para>This is a target that is called whever the SysV compatibility code asks for runlevel 3. It is a good idea to make this an alias for (i.e. symlink to) <filename>multi-user.target</filename> or <filename>graphical.target</filename>.</para> </listitem> </varlistentry> <varlistentry> <term><filename>runlevel4.target</filename></term> <listitem> <para>This is a target that is called whever the SysV compatibility code asks for runlevel 4. It is a good idea to make this an alias for (i.e. symlink to) <filename>multi-user.target</filename> or <filename>graphical.target</filename>.</para> </listitem> </varlistentry> <varlistentry> <term><filename>runlevel5.target</filename></term> <listitem> <para>This is a target that is called whever the SysV compatibility code asks for runlevel 5. It is a good idea to make this an alias for (i.e. symlink to) <filename>multi-user.target</filename> or <filename>graphical.target</filename>.</para> </listitem> </varlistentry> <varlistentry> <term><filename>runlevel6.target</filename></term> <listitem> <para>This is a target that is called whever the SysV compatibility code asks for runlevel 6. This is an alias for <filename>reboot.target</filename>, for compatibility with SysV.</para> </listitem> </varlistentry> <varlistentry> <term><filename>shutdown.target</filename></term> <listitem> <para>A special target unit that terminates the services on system shutdown.</para> <para>Services that shall be terminated on system shutdown shall add Conflicts dependencies to this unit for their service unit during installation.</para> <para>systemd automatically adds dependencies of type Conflicts to this target unit for all SysV init script service units that shall be terminated in SysV runlevels 0 or 6.</para> </listitem> </varlistentry> <varlistentry> <term><filename>sigpwr.target</filename></term> <listitem> <para>A special target that is started when systemd receives the SIGPWR process signal, which is normally sent by the kernel or UPS daemons when power fails.</para> </listitem> </varlistentry> <varlistentry> <term><filename>sockets.target</filename></term> <listitem> <para>A special target unit that sets up all service sockets.</para> <para>Services that can be socket-activated shall add Wants dependencies to this unit for their socket unit during installation.</para> </listitem> </varlistentry> <varlistentry> <term><filename>swap.target</filename></term> <listitem> <para>Similar to <filename>local-fs.target</filename>, but for swap partitions and swap files.</para> </listitem> </varlistentry> <varlistentry> <term><filename>syslog.target</filename></term> <listitem> <para>systemd automatically adds dependencies of type After for this target unit to all SysV init script service units with an LSB header referring to the <literal>$syslog</literal> facility.</para> <para>Administrators should ensure that this target pulls in a service unit with the name or alias of <filename>@SPECIAL_SYSLOG_SERVICE@</filename> (or a socket unit that activates this service).</para> </listitem> </varlistentry> <varlistentry> <term><filename>@SPECIAL_SYSLOG_SERVICE@</filename></term> <listitem> <para>A special unit for the syslog daemon. As soon as this service is fully started up systemd will connect to it and use it for logging if it has been configured for that.</para> <para>Applications should generally not depend on this service, and depend on <filename>syslog.target</filename> instead.</para> </listitem> </varlistentry> <varlistentry> <term><filename>systemd-initctl.service</filename></term> <listitem> <para>This provides compatibility with the SysV /dev/initctl file system FIFO for communication with the init system.</para> <para>This is a socket-activated service, see <filename>system-initctl.socket</filename>.</para> </listitem> </varlistentry> <varlistentry> <term><filename>systemd-initctl.socket</filename></term> <listitem> <para>Socket activation unit for <filename>system-initctl.service</filename>.</para> </listitem> </varlistentry> <varlistentry> <term><filename>systemd-logger.service</filename></term> <listitem> <para>This is internally used by systemd to provide syslog logging to the processes it maintains.</para> <para>This is a socket-activated service, see <filename>system-logger.socket</filename>.</para> </listitem> </varlistentry> <varlistentry> <term><filename>systemd-logger.socket</filename></term> <listitem> <para>Socket activation unit for <filename>system-logger.service</filename>. systemd will automatically add dependencies of types Requires and After to all units that have been configured for stdout or stderr to be connected to syslog or the kernel log buffer.</para> </listitem> </varlistentry> </variablelist> </refsect1> <refsect1> <title>Special Session Units</title> <para>When systemd runs as a service instance, the following special units are available, which have similar definitions as their system counterparts: <filename>default.target</filename>, <filename>local-fs.target</filename>, <filename>remote-fs.target</filename>, <filename>shutdown.target</filename>, <filename>sockets.target</filename>, <filename>swap.target</filename>.</para> <para>In addition the following special unit is understood only when systemd runs as service instance:</para> <variablelist> <varlistentry> <term><filename>exit.service</filename></term> <listitem> <para>A special service unit for shutting down the session.</para> <para>Applications wanting to terminate the session should start this unit. If systemd receives SIGTERM or SIGINT when running as session daemon it will start this unit.</para> <para>Normally, this pulls in <filename>shutdown.target</filename> which in turn should be conflicted by all units that want to be shut down on session exit.</para> </listitem> </varlistentry> </variablelist> </refsect1> <refsect1> <title>See Also</title> <para> <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry> <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry> <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry> <citerefentry><refentrytitle>systemd.target</refentrytitle><manvolnum>5</manvolnum></citerefentry> </para> </refsect1> </refentry>