-<?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*-->
+<?xml version='1.0'?>
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
<!--
SPDX-License-Identifier: LGPL-2.1+
-
- 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 Lesser General Public License as published by
- the Free Software Foundation; either version 2.1 of the License, or
- (at your option) any later version.
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- 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
- Lesser General Public License for more details.
-
- You should have received a copy of the GNU Lesser General Public License
- along with systemd; If not, see <http://www.gnu.org/licenses/>.
-->
<refentry id="systemd"
<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>
outputs a terse but complete list of configuration items
understood in unit definition files.</para></listitem>
</varlistentry>
+ <varlistentry>
+ <term><option>--dump-bus-properties</option></term>
+
+ <listitem><para>Dump exposed bus properties. This outputs
+ a terse but complete list of properties exposed to dbus.
+ </para></listitem>
+ </varlistentry>
<varlistentry>
<term><option>--unit=</option></term>
to all zeros.</para></listitem>
</varlistentry>
+ <varlistentry>
+ <term><option>--service-watchdogs=</option></term>
+
+ <listitem><para>Globally enable/disable all service watchdog timeouts and emergency
+ actions. This setting may also be specified during boot, on the kernel
+ command line via the <varname>systemd.service_watchdogs=</varname>
+ option, see below. Defaults to enabled.</para></listitem>
+ </varlistentry>
+
<xi:include href="standard-options.xml" xpointer="help" />
<xi:include href="standard-options.xml" xpointer="version" />
</variablelist>
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>
+ (process returned error code on exit, or crashed, an operation
+ timed out, or after too many restarts). 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>
<citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry>
for details about these target units.</para>
+ <para>systemd only keeps a minimal set of units loaded into memory. Specifically, the only units that are kept
+ loaded into memory are those for which at least one of the following conditions is true:</para>
+
+ <orderedlist>
+ <listitem><para>It is in an active, activating, deactivating or failed state (i.e. in any unit state except for <literal>inactive</literal>)</para></listitem>
+ <listitem><para>It has a job queued for it</para></listitem>
+ <listitem><para>It is a dependency of some sort of at least one other unit that is loaded into memory</para></listitem>
+ <listitem><para>It has some form of resource still allocated (e.g. a service unit that is inactive but for which
+ a process is still lingering that ignored the request to be terminated)</para></listitem>
+ <listitem><para>It has been pinned into memory programmatically by a D-Bus call</para></listitem>
+ </orderedlist>
+
+ <para>systemd will automatically and implicitly load units from disk — if they are not loaded yet — as soon as
+ operations are requested for them. Thus, in many respects, the fact whether a unit is loaded or not is invisible to
+ clients. Use <command>systemctl list-units --all</command> to comprehensively list all units currently loaded. Any
+ unit for which none of the conditions above applies is promptly unloaded. Note that when a unit is unloaded from
+ memory its accounting data is flushed out too. However, this data is generally not lost, as a journal log record
+ is generated declaring the consumed resources whenever a unit shuts down.</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>
+ url="https://www.kernel.org/doc/Documentation/cgroup-v1/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
verify that it makes sense, fixing it if possible, and only
failing if it really cannot work.</para>
+ <para>Note that transactions are generated independently of a unit's
+ state at runtime, hence, for example, if a start job is requested on an
+ already started unit, it will still generate a transaction and wake up any
+ inactive dependencies (and cause propagation of other jobs as per the
+ defined relationships). This is because the enqueued job is at the time of
+ execution compared to the target unit's state and is marked successful and
+ complete when both satisfy. However, this job also pulls in other
+ dependencies due to the defined relationships and thus leads to, in our
+ our example, start jobs for any of those inactive units getting queued as
+ well.</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
<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
- --job-mode=replace-irreversible</command>. If this signal is
- received more 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>
+ <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 ctrl-alt-del.target --job-mode=replace-irreversible</command>. If
+ this signal is received more than 7 times per 2s, an immediate reboot is triggered. Note
+ that pressing
+ <keycombo><keycap>Ctrl</keycap><keycap>Alt</keycap><keycap>Del</keycap></keycombo> on the
+ console will trigger this signal. Hence, if a reboot is hanging, pressing
+ <keycombo><keycap>Ctrl</keycap><keycap>Alt</keycap><keycap>Del</keycap></keycombo> more than
+ 7 times in 2 seconds 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>
<term><constant>SIGRTMIN+22</constant></term>
+
+ <listitem><para>Sets the service manager's log level to <literal>debug</literal>, in a fashion equivalent to
+ <varname>systemd.log_level=debug</varname> on the kernel command line.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
<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>
+ <listitem><para>Restores the log level to its configured value. The configured value is derived from – in order
+ of priority – the value specified with <varname>systemd.log-level=</varname> on the kernel command line, or the
+ value specified with <option>LogLevel=</option> in the configuration file, or the built-in default of
+ <literal>info</literal>.</para></listitem>
</varlistentry>
<varlistentry>
<varlistentry>
<term><constant>SIGRTMIN+26</constant></term>
+
+ <listitem><para>Restores the log target to its configured value. The configured value is derived from – in
+ order of priority – the value specified with <varname>systemd.log-target=</varname> on the kernel command line,
+ or the value specified with <option>LogTarget=</option> in the configuration file, or the built-in
+ default.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
<term><constant>SIGRTMIN+27</constant></term>
<term><constant>SIGRTMIN+28</constant></term>
- <listitem><para>Sets the log target 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>
+ <listitem><para>Sets the log target to <literal>console</literal> on <constant>SIGRTMIN+27</constant> (or
+ <literal>kmsg</literal> on <constant>SIGRTMIN+28</constant>), in a fashion equivalent to
+ <varname>systemd.log_target=console</varname> (or <varname>systemd.log_target=kmsg</varname> on
+ <constant>SIGRTMIN+28</constant>) on the kernel command line.</para></listitem>
</varlistentry>
</variablelist>
</refsect1>
</listitem>
</varlistentry>
+ <varlistentry>
+ <term><varname>$SYSTEMD_URLIFY</varname></term>
+
+ <listitem><para>The value must be a boolean. Controls whether clickable links should be generated in the output
+ for terminal emulators supporting this. This can be specified to override the decision that
+ <command>systemd</command> makes based on <varname>$TERM</varname> and other conditions.</para>
+ </listitem>
+ </varlistentry>
+
<varlistentry>
<term><varname>$LISTEN_PID</varname></term>
<term><varname>$LISTEN_FDS</varname></term>
for more information.</para></listitem>
</varlistentry>
</variablelist>
+
+ <para>For further environment variables understood by systemd and its various components, see <ulink
+ url="https://systemd.io/ENVIRONMENT">Known Environment Variables</ulink>.</para>
</refsect1>
<refsect1>
</para></listitem>
</varlistentry>
+ <varlistentry>
+ <term><varname>systemd.service_watchdogs=</varname></term>
+
+ <listitem><para>Takes a boolean argument. If disabled, all service runtime
+ watchdogs (<option>WatchdogSec=</option>) and emergency actions (e.g.
+ <option>OnFailure=</option> or <option>StartLimitAction=</option>) are
+ ignored by the system manager (PID 1); see
+ <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
+ Defaults to enabled, i.e. watchdogs and failure actions are processed
+ normally. The hardware watchdog is not affected by this
+ option.</para></listitem>
+ </varlistentry>
+
<varlistentry>
<term><varname>systemd.show_status</varname></term>
hybrid or full legacy cgroup hierarchy.</para>
<para>If this option is not specified, the default behaviour is determined
- during compilation (the <option>--with-default-hierarchy=</option>
+ during compilation (the <option>-Ddefault-hierarchy=</option> meson
option). If the kernel does not support unified cgroup hierarchy, the legacy
hierarchy will be used even if this option is specified.</para>
</listitem>
the use of "hybrid" hierarchy.</para>
<para>If this option is not specified, the default behaviour is determined
- during compilation (the <option>--with-default-hierarchy=</option>
+ during compilation (the <option>-Ddefault-hierarchy=</option> meson
option). If the kernel does not support unified cgroup hierarchy, the legacy
hierarchy will be used even if this option is specified.</para>
</listitem>
<term><varname>quiet</varname></term>
<listitem><para>Turn off status output at boot, much like
- <varname>systemd.show_status=false</varname> would. Note that
+ <varname>systemd.show_status=no</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.
projects / thirdparty / systemd.git / blobdiff