mirror of
https://github.com/systemd/systemd.git
synced 2024-11-05 06:52:22 +03:00
590 lines
33 KiB
XML
590 lines
33 KiB
XML
<?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.unit">
|
|
|
|
<refentryinfo>
|
|
<title>systemd.unit</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.unit</refentrytitle>
|
|
<manvolnum>5</manvolnum>
|
|
</refmeta>
|
|
|
|
<refnamediv>
|
|
<refname>systemd.unit</refname>
|
|
<refpurpose>systemd unit configuration files</refpurpose>
|
|
</refnamediv>
|
|
|
|
<refsynopsisdiv>
|
|
<para><filename>systemd.service</filename>,
|
|
<filename>systemd.socket</filename>,
|
|
<filename>systemd.device</filename>,
|
|
<filename>systemd.mount</filename>,
|
|
<filename>systemd.automount</filename>,
|
|
<filename>systemd.swap</filename>,
|
|
<filename>systemd.target</filename>,
|
|
<filename>systemd.path</filename>,
|
|
<filename>systemd.timer</filename>,
|
|
<filename>systemd.snapshot</filename></para>
|
|
</refsynopsisdiv>
|
|
|
|
<refsect1>
|
|
<title>Description</title>
|
|
|
|
<para>A unit configuration file encodes information
|
|
about a service, a socket, a device, a mount point, an
|
|
automount point, a swap file or partition, a start-up
|
|
target, a file system path or a timer controlled and
|
|
supervised by
|
|
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>. The
|
|
syntax is inspired by <ulink
|
|
url="http://standards.freedesktop.org/desktop-entry-spec/latest/">XDG
|
|
Desktop Entry Specification</ulink> <filename>.desktop</filename> files, which are in turn
|
|
inspired by Microsoft Windows
|
|
<filename>.ini</filename> files.</para>
|
|
|
|
<para>This man pages lists the common configuration
|
|
options of all the unit types. These options need to
|
|
be configured in the [Unit] resp. [Install]
|
|
section of the unit files.</para>
|
|
|
|
<para>In addition to the generic [Unit] and [Install]
|
|
sections described here, each unit should have a
|
|
type-specific section, e.g. [Service] for a service
|
|
unit. See the respective man pages for more
|
|
information.</para>
|
|
|
|
<para>Unit files may contain additional options on top
|
|
of those listed here. If systemd encounters an unknown
|
|
option it will write a warning log message but
|
|
continue loading the unit. If an option is prefixed
|
|
with <option>X-</option> it is ignored completely by
|
|
systemd. Applications may use this to include
|
|
additional information in the unit files.</para>
|
|
|
|
<para>Boolean arguments used in unit files can be
|
|
written in various formats. For positive settings the
|
|
strings <option>1</option>, <option>yes</option>,
|
|
<option>true</option> and <option>on</option> are
|
|
equivalent. For negative settings the strings
|
|
<option>0</option>, <option>no</option>,
|
|
<option>false</option> and <option>off</option> are
|
|
equivalent.</para>
|
|
|
|
<para>Time span values encoded in unit files can be
|
|
written in various formats. A stand-alone number
|
|
specifies a time in seconds. If suffixed with a time
|
|
unit, the unit is honored. A concatenation of
|
|
multiple values with units is supported, in which case
|
|
the values are added up. Example: "50" refers to 50
|
|
seconds; "2min 200ms" refers to 2 minutes plus 200
|
|
milliseconds, i.e. 120200ms. The following time units
|
|
are understood: s, min, h, d, w, ms, us.</para>
|
|
|
|
<para>Empty lines and lines starting with # or ; are
|
|
ignored. This may be used for commenting. Lines ending
|
|
in a backslash are concatenated with the following
|
|
line while reading and the backslash is replaced by a
|
|
space character. This may be used to wrap long lines.</para>
|
|
|
|
<para>If a line starts with <option>.include</option>
|
|
followed by a file name, the specified file will be
|
|
read as if its contents were listed in place of the
|
|
<option>.include</option> directive.</para>
|
|
|
|
<para>Along with a unit file
|
|
<filename>foo.service</filename> a directory
|
|
<filename>foo.service.wants/</filename> may exist. All
|
|
units symlinked from such a directory are implicitly
|
|
added as dependencies of type
|
|
<varname>Wanted=</varname> to the unit. This is useful
|
|
to hook units into the start-up of other units,
|
|
without having to modify their unit configuration
|
|
files. For details about the semantics of
|
|
<varname>Wanted=</varname> see below. The preferred
|
|
way to create symlinks in the
|
|
<filename>.wants/</filename> directory of a service is
|
|
with the
|
|
<citerefentry><refentrytitle>systemd-install</refentrytitle><manvolnum>1</manvolnum></citerefentry>
|
|
tool which reads information from the [Install]
|
|
section of unit files. (See below.)</para>
|
|
|
|
<para>Note that while systemd offers a flexible
|
|
dependency system between units it is recommended to
|
|
use this functionality only sparsely and instead rely
|
|
on techniques such as bus-based or socket-based
|
|
activation which makes dependencies implicit, which
|
|
both results in a simpler and more flexible
|
|
system.</para>
|
|
|
|
<para>Some unit names reflect paths existing in the
|
|
file system name space. Example: a device unit
|
|
<filename>dev-sda.device</filename> refers to a device
|
|
with the device node <filename>/dev/sda</filename> in
|
|
the file system namespace. If this applies a special
|
|
way to escape the path name is used, so that the
|
|
result is usable as part of a file name. Basically,
|
|
given a path, "/" is replaced by "-", and all
|
|
unprintable characters and the "-" are replaced by
|
|
C-style "\x20" escapes. The root directory "/" is
|
|
encoded as single dash, while otherwise the initial
|
|
and ending "/" is removed from all paths during
|
|
transformation. This escaping is reversible.</para>
|
|
|
|
<para>Optionally, units may be instantiated from a
|
|
template file at runtime. This allows creation of
|
|
multiple units from a single configuration file. If
|
|
systemd looks for a unit configuration file it will
|
|
first search for the literal unit name in the
|
|
filesystem. If that yields no success and the unit
|
|
name contains an @ character, systemd will look for a
|
|
unit template that shares the same name but with the
|
|
instance string (i.e. the part between the @ character
|
|
and the suffix) removed. Example: if a service
|
|
<filename>getty@tty3.service</filename> is requested
|
|
and no file by that name is found, systemd will look
|
|
for <filename>getty@.service</filename> and
|
|
instantiate a service from that configuration file if
|
|
it is found. To refer to the instance string from
|
|
within the configuration file you may use the special
|
|
<literal>%i</literal> specifier in many of the
|
|
configuration options. Other specifiers that may be
|
|
used are <literal>%n</literal>, <literal>%N</literal>,
|
|
<literal>%p</literal>, <literal>%P</literal> and
|
|
<literal>%I</literal>, for the full unit name, the
|
|
unescaped unit name, the prefix name, the unescaped
|
|
prefix name and the unescaped instance name,
|
|
respectively. The prefix name here refers to the
|
|
string before the @, i.e. "getty" in the example
|
|
above, where "tty3" is the instance name.</para>
|
|
</refsect1>
|
|
|
|
<refsect1>
|
|
<title>Options</title>
|
|
|
|
<para>Unit file may include a [Unit] section, which
|
|
carries generic information about the unit that is not
|
|
dependent on the type of unit:</para>
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term><varname>Names=</varname></term>
|
|
|
|
<listitem><para>Additional names for
|
|
this unit. The names listed here must
|
|
have the same suffix (i.e. type) as
|
|
the unit file name. This option may be
|
|
specified more than once, in which
|
|
case all listed names are used. Note
|
|
that this option is different from the
|
|
<varname>Alias=</varname> option from
|
|
the [Install] section mentioned
|
|
below. See below for details.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><varname>Description=</varname></term>
|
|
<listitem><para>A free-form string
|
|
describing the unit. This is intended
|
|
for use in UIs to show descriptive
|
|
information along with the unit
|
|
name.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><varname>Requires=</varname></term>
|
|
|
|
<listitem><para>Configures requirement
|
|
dependencies on other units. If this
|
|
unit gets activated, the units listed
|
|
here will be activated as well. If one
|
|
of the other units gets deactivated or
|
|
its activation fails, this unit will
|
|
be deactivated. This option may be
|
|
specified more than once, in which
|
|
case requirement dependencies for all
|
|
listed names are created. Note that
|
|
requirement dependencies do not
|
|
influence the order in which services
|
|
are started or stopped. This has to be
|
|
configured independently with the
|
|
<varname>After=</varname> or
|
|
<varname>Before=</varname> options. If
|
|
a unit
|
|
<filename>foo.service</filename>
|
|
requires a unit
|
|
<filename>bar.service</filename> as
|
|
configured with
|
|
<varname>Requires=</varname> and no
|
|
ordering is configured with
|
|
<varname>After=</varname> or
|
|
<varname>Before=</varname>, then both
|
|
units will be started simultaneously
|
|
and without any delay between them if
|
|
<filename>foo.service</filename> is
|
|
activated. Often it is a better choice
|
|
to use <varname>Wants=</varname>
|
|
instead of
|
|
<varname>Requires=</varname> in order
|
|
to achieve a system that is more
|
|
robust when dealing with failing
|
|
services.</para></listitem>
|
|
</varlistentry>
|
|
|
|
|
|
<varlistentry>
|
|
<term><varname>RequiresOverridable=</varname></term>
|
|
|
|
<listitem><para>Similar to
|
|
<varname>Requires=</varname>.
|
|
Dependencies listed in
|
|
<varname>RequiresOverridable=</varname>
|
|
which cannot be fulfilled or fail to
|
|
start are ignored if the startup was
|
|
explicitly requested by the user. If
|
|
the start-up was pulled in indirectly
|
|
by some dependency or automatic
|
|
start-up of units that is not
|
|
requested by the user this dependency
|
|
must be fulfilled and otherwise the
|
|
transaction fails. Hence, this option
|
|
may be used to configure dependencies
|
|
that are normally honored unless the
|
|
user explicitly starts up the unit, in
|
|
which case whether they failed or not
|
|
is irrelevant.</para></listitem>
|
|
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><varname>Requisite=</varname></term>
|
|
<term><varname>RequisiteOverridable=</varname></term>
|
|
|
|
<listitem><para>Similar to
|
|
<varname>Requires=</varname>
|
|
resp. <varname>RequiresOverridable=</varname>. However,
|
|
if a unit listed here is not started
|
|
already it will not be started and the
|
|
transaction fails
|
|
immediately.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><varname>Wants=</varname></term>
|
|
|
|
<listitem><para>A weaker version of
|
|
<varname>Requires=</varname>. A unit
|
|
listed in this option will be started
|
|
if the configuring unit is. However,
|
|
if the listed unit fails to start up
|
|
or cannot be added to the transaction
|
|
this has no impact on the validity of
|
|
the transaction as a whole. This is
|
|
the recommended way to hook start-up
|
|
of one unit to the start-up of another
|
|
unit. Note that dependencies of this
|
|
type may also be configured outside of
|
|
the unit configuration file by
|
|
adding a symlink to a
|
|
<filename>.wants/</filename> directory
|
|
accompanying the unit file. For
|
|
details see above.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><varname>Conflicts=</varname></term>
|
|
|
|
<listitem><para>Configures negative
|
|
requirement dependencies. If a unit
|
|
has a
|
|
<varname>Conflicts=</varname> setting
|
|
on another unit, starting the former
|
|
will stop the latter and vice
|
|
versa. Note that this setting is
|
|
independent of and orthogonal to the
|
|
<varname>After=</varname> and
|
|
<varname>Before=</varname> ordering
|
|
dependencies.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><varname>Before=</varname></term>
|
|
<term><varname>After=</varname></term>
|
|
|
|
<listitem><para>Configures ordering
|
|
dependencies between units. If a unit
|
|
<filename>foo.service</filename>
|
|
contains a setting
|
|
<option>Before=bar.service</option>
|
|
and both units are being started,
|
|
<filename>bar.service</filename>'s
|
|
start-up is delayed until
|
|
<filename>foo.service</filename> is
|
|
started up. Note that this setting is
|
|
independent of and orthogonal to the
|
|
requirement dependencies as configured
|
|
by <varname>Requires=</varname>. It is
|
|
a common pattern to include a unit
|
|
name in both the
|
|
<varname>After=</varname> and
|
|
<varname>Requires=</varname> option in
|
|
which case the unit listed will be
|
|
started before the unit that is
|
|
configured with these options. This
|
|
option may be specified more than
|
|
once, in which case ordering
|
|
dependencies for all listed names are
|
|
created. <varname>After=</varname> is
|
|
the inverse of
|
|
<varname>Before=</varname>, i.e. while
|
|
<varname>After=</varname> ensures that
|
|
the configured unit is started after
|
|
the listed unit finished starting up,
|
|
<varname>Before=</varname> ensures the
|
|
opposite, i.e. that the configured
|
|
unit is fully started up before the
|
|
listed unit is started. Note that when
|
|
two units with an ordering dependency
|
|
between them are shut down, the
|
|
inverse of the start-up order is
|
|
applied. i.e. if a unit is configured
|
|
with <varname>After=</varname> on
|
|
another unit, the former is stopped
|
|
before the latter if both are shut
|
|
down. If one unit with an ordering
|
|
dependency on another unit is shut
|
|
down while the latter is started up,
|
|
the shut down is ordered before the
|
|
start-up regardless whether the
|
|
ordering dependency is actually of
|
|
type <varname>After=</varname> or
|
|
<varname>Before=</varname>. If two
|
|
units have no ordering dependencies
|
|
between them they are shut down
|
|
resp. started up simultaneously, and
|
|
no ordering takes
|
|
place. </para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><varname>RecursiveStop=</varname></term>
|
|
|
|
<listitem><para>Takes a boolean
|
|
argument. If <option>true</option> and
|
|
the unit stops without being requested
|
|
by the user, all units
|
|
depending on it will be stopped as
|
|
well. (e.g. if a service exits or
|
|
crashes on its own behalf, units using
|
|
it will be stopped) Note that normally
|
|
if a unit stops without a user request,
|
|
units depending on it will not be
|
|
terminated. Only if the user requested
|
|
shutdown of a unit, all units depending
|
|
on that unit will be shut down as well
|
|
and at the same time. Defaults to
|
|
<option>false</option>.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><varname>StopWhenUnneeded=</varname></term>
|
|
|
|
<listitem><para>Takes a boolean
|
|
argument. If <option>true</option>
|
|
this unit will be stopped when it is
|
|
no longer used. Note that in order to
|
|
minimize the work to be executed,
|
|
systemd will not stop units by default
|
|
unless they are conflicting with other
|
|
units, or the user explicitly
|
|
requested their shut down. If this
|
|
option is set, a unit will be
|
|
automatically cleaned up if no other
|
|
active unit requires it. Defaults to
|
|
<option>false</option>.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><varname>OnlyByDependency=</varname></term>
|
|
|
|
<listitem><para>Takes a boolean
|
|
argument. If <option>true</option>
|
|
this unit can only be activated
|
|
indirectly. In this case explicit
|
|
start-up requested by the user is
|
|
denied, however if it is started as a
|
|
dependency of another unit, start-up
|
|
will succeed. This is mostly a safety
|
|
feature to ensure that the user does
|
|
not accidentally activate units that are
|
|
not intended to be activated
|
|
explicitly. This option defaults to
|
|
<option>false</option>.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><varname>DefaultDependencies=</varname></term>
|
|
|
|
<listitem><para>Takes a boolean
|
|
argument. If <option>true</option>
|
|
(the default), a few default
|
|
dependencies will implicitly be
|
|
created for the unit. The actual
|
|
dependencies created depend on the
|
|
unit type. For example, for service
|
|
units, these dependencies ensure that
|
|
the service is started only after
|
|
basic system initialization is
|
|
completed and is properly terminated on
|
|
system shutdown. See the respective
|
|
man pages for details. Generally, only
|
|
services involved with early boot or
|
|
late shutdown should set this option
|
|
to <option>false</option>. It is
|
|
highly recommended to leave this
|
|
option enabled for the majority of
|
|
common units. If set to
|
|
<option>false</option> this option
|
|
does not disable all implicit
|
|
dependencies, just non-essential
|
|
ones.</para></listitem>
|
|
</varlistentry>
|
|
|
|
</variablelist>
|
|
|
|
<para>Unit file may include a [Install] section, which
|
|
carries installation information for the unit. This
|
|
section is not interpreted by
|
|
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>
|
|
during runtime. It is used exclusively by the
|
|
<citerefentry><refentrytitle>systemd-install</refentrytitle><manvolnum>1</manvolnum></citerefentry>
|
|
tool during installation of a unit:</para>
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term><varname>Alias=</varname></term>
|
|
|
|
<listitem><para>Additional names this
|
|
unit shall be installed under. The
|
|
names listed here must have the same
|
|
suffix (i.e. type) as the unit file
|
|
name. This option may be specified
|
|
more than once, in which case all
|
|
listed names are used. At installation
|
|
time,
|
|
<command>systemd-install</command>
|
|
will create symlinks from these names
|
|
to the unit file name. Note that this
|
|
is different from the
|
|
<varname>Names=</varname> option from
|
|
the [Unit] section mentioned above:
|
|
The names from
|
|
<varname>Names=</varname> apply
|
|
unconditionally if the unit is
|
|
loaded. The names from
|
|
<varname>Alias=</varname> apply only
|
|
if the unit has actually been
|
|
installed with the
|
|
<command>systemd-install</command>
|
|
tool. Also, if systemd searches for a
|
|
unit, it will discover symlinked alias
|
|
names as configured with
|
|
<varname>Alias=</varname>, but not
|
|
names configured with
|
|
<varname>Names=</varname> only. It is
|
|
a common pattern to list a name in
|
|
both options. In this case, a unit
|
|
will be active under all names if
|
|
installed, but also if not installed
|
|
but requested explicitly under its
|
|
main name.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><varname>WantedBy=</varname></term>
|
|
|
|
<listitem><para>Installs a symlink in
|
|
the <filename>.wants/</filename>
|
|
subdirectory for a unit. This has the
|
|
effect that when the listed unit name
|
|
is activated the unit listing it is
|
|
activated
|
|
too. <command>WantedBy=foo.service</command>
|
|
in a service
|
|
<filename>bar.service</filename> is
|
|
mostly equivalent to
|
|
<command>Alias=foo.service.wants/bar.service</command>
|
|
in the same file.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><varname>Also=</varname></term>
|
|
|
|
<listitem><para>Additional units to
|
|
install when this unit is
|
|
installed. If the user requests
|
|
installation of a unit with this
|
|
option configured,
|
|
<command>systemd-install</command>
|
|
will automatically install units
|
|
listed in this option as
|
|
well.</para></listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
|
|
</refsect1>
|
|
|
|
<refsect1>
|
|
<title>See Also</title>
|
|
<para>
|
|
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
|
|
<citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
|
|
<citerefentry><refentrytitle>systemd-install</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
|
|
<citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
|
|
<citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
|
|
<citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
|
|
<citerefentry><refentrytitle>systemd.device</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
|
|
<citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
|
|
<citerefentry><refentrytitle>systemd.automount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
|
|
<citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
|
|
<citerefentry><refentrytitle>systemd.target</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
|
|
<citerefentry><refentrytitle>systemd.path</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
|
|
<citerefentry><refentrytitle>systemd.timer</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
|
|
<citerefentry><refentrytitle>systemd.snapshot</refentrytitle><manvolnum>5</manvolnum></citerefentry>
|
|
</para>
|
|
</refsect1>
|
|
|
|
</refentry>
|