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<html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>systemd</title><meta name="generator" content="DocBook XSL Stylesheets V1.78.1"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><style>
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</style><a href="index.html">Index </a>·
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<a href="../python-systemd/index.html">Python </a>·
<a href="../libudev/index.html">libudev </a>·
<a href="../libudev/index.html">gudev </a><span style="float:right">systemd 215</span><hr><div class="refentry"><a name="systemd"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>systemd, init — systemd system and service manager</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><div class="cmdsynopsis"><p><code class="command">systemd [OPTIONS...]</code> </p></div><div class="cmdsynopsis"><p><code class="command">init [OPTIONS...] {COMMAND}</code> </p></div></div><div class="refsect1"><a name="idm214189898832"></a><h2 id="Description">Description<a class="headerlink" title="Permalink to this headline" href="#Description">¶</a></h2><p>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.</p><p>For compatibility with SysV, if systemd is called
as <span class="command"><strong>init</strong></span> and a PID that is not
1, it will execute <span class="command"><strong>telinit</strong></span> and pass
all command line arguments unmodified. That means
<span class="command"><strong>init</strong></span> and <span class="command"><strong>telinit</strong></span>
are mostly equivalent when invoked from normal login sessions. See
<a href="telinit.html"><span class="citerefentry"><span class="refentrytitle">telinit</span>(8)</span></a>
for more information.</p><p>When run as system instance, systemd interprets
the configuration file
<code class="filename">system.conf</code>, otherwise
<code class="filename">user.conf</code>. See
<a href="systemd-system.conf.html"><span class="citerefentry"><span class="refentrytitle">systemd-system.conf</span>(5)</span></a>
for more information.</p></div><div class="refsect1"><a name="idm214188084384"></a><h2 id="Options">Options<a class="headerlink" title="Permalink to this headline" href="#Options">¶</a></h2><p>The following options are understood:</p><div class="variablelist"><dl class="variablelist"><dt id="--test"><span class="term"><code class="option">--test</code></span><a class="headerlink" title="Permalink to this term" href="#--test">¶</a></dt><dd><p>Determine startup
sequence, dump it and exit. This is an
option useful for debugging
only.</p></dd><dt id="--dump-configuration-items"><span class="term"><code class="option">--dump-configuration-items</code></span><a class="headerlink" title="Permalink to this term" href="#--dump-configuration-items">¶</a></dt><dd><p>Dump understood unit
configuration items. This outputs a
terse but complete list of
configuration items understood in unit
definition files.</p></dd><dt id="--unit="><span class="term"><code class="option">--unit=</code></span><a class="headerlink" title="Permalink to this term" href="#--unit=">¶</a></dt><dd><p>Set default unit to
activate on startup. If not specified,
defaults to
<code class="filename">default.target</code>.</p></dd><dt id="--system"><span class="term"><code class="option">--system</code>, </span><span class="term"><code class="option">--user</code></span><a class="headerlink" title="Permalink to this term" href="#--system">¶</a></dt><dd><p>For <code class="option">--system</code>,
tell systemd to run a
system instance, even if the process ID is
not 1, i.e. systemd is not run as init process.
<code class="option">--user</code> 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 <code class="option">--system</code>
mode, but PID not 1. In practice,
passing <code class="option">--system</code> explicitly is
only useful in conjunction with
<code class="option">--test</code>.</p></dd><dt id="--dump-core"><span class="term"><code class="option">--dump-core</code></span><a class="headerlink" title="Permalink to this term" href="#--dump-core">¶</a></dt><dd><p>Dump core on
crash. This switch has no effect when
run as user
instance.</p></dd><dt id="--crash-shell"><span class="term"><code class="option">--crash-shell</code></span><a class="headerlink" title="Permalink to this term" href="#--crash-shell">¶</a></dt><dd><p>Run shell on
crash. This switch has no effect when
run as user
instance.</p></dd><dt id="--confirm-spawn"><span class="term"><code class="option">--confirm-spawn</code></span><a class="headerlink" title="Permalink to this term" href="#--confirm-spawn">¶</a></dt><dd><p>Ask for confirmation
when spawning processes. This switch
has no effect when run as user
instance.</p></dd><dt id="--show-status="><span class="term"><code class="option">--show-status=</code></span><a class="headerlink" title="Permalink to this term" href="#--show-status=">¶</a></dt><dd><p>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
<code class="option">true</code>.</p></dd><dt id="--log-target="><span class="term"><code class="option">--log-target=</code></span><a class="headerlink" title="Permalink to this term" href="#--log-target=">¶</a></dt><dd><p>Set log
target. Argument must be one of
<code class="option">console</code>,
<code class="option">journal</code>,
<code class="option">syslog</code>,
<code class="option">kmsg</code>,
<code class="option">journal-or-kmsg</code>,
<code class="option">syslog-or-kmsg</code>,
<code class="option">null</code>.</p></dd><dt id="--log-level="><span class="term"><code class="option">--log-level=</code></span><a class="headerlink" title="Permalink to this term" href="#--log-level=">¶</a></dt><dd><p>Set log level. As
argument this accepts a numerical log
level or the well-known <a href="syslog.html"><span class="citerefentry"><span class="refentrytitle">syslog</span>(3)</span></a>
symbolic names (lowercase):
<code class="option">emerg</code>,
<code class="option">alert</code>,
<code class="option">crit</code>,
<code class="option">err</code>,
<code class="option">warning</code>,
<code class="option">notice</code>,
<code class="option">info</code>,
<code class="option">debug</code>.</p></dd><dt id="--log-color="><span class="term"><code class="option">--log-color=</code></span><a class="headerlink" title="Permalink to this term" href="#--log-color=">¶</a></dt><dd><p>Highlight important
log messages. Argument is a boolean
value. If the argument is omitted, it
defaults to
<code class="option">true</code>.</p></dd><dt id="--log-location="><span class="term"><code class="option">--log-location=</code></span><a class="headerlink" title="Permalink to this term" href="#--log-location=">¶</a></dt><dd><p>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
<code class="option">true</code>.</p></dd><dt id="--default-standard-output="><span class="term"><code class="option">--default-standard-output=</code>, </span><span class="term"><code class="option">--default-standard-error=</code></span><a class="headerlink" title="Permalink to this term" href="#--default-standard-output=">¶</a></dt><dd><p>Sets the default
output or error output for all
services and sockets, respectively. That is, controls
the default for
<code class="option">StandardOutput=</code>
and <code class="option">StandardError=</code>
(see
<a href="systemd.exec.html"><span class="citerefentry"><span class="refentrytitle">systemd.exec</span>(5)</span></a>
for details). Takes one of
<code class="option">inherit</code>,
<code class="option">null</code>,
<code class="option">tty</code>,
<code class="option">journal</code>,
<code class="option">journal+console</code>,
<code class="option">syslog</code>,
<code class="option">syslog+console</code>,
<code class="option">kmsg</code>,
<code class="option">kmsg+console</code>. If the
argument is omitted
<code class="option">--default-standard-output=</code>
defaults to <code class="option">journal</code>
and
<code class="option">--default-standard-error=</code>
to
<code class="option">inherit</code>.</p></dd><dt id="-h"><span class="term"><code class="option">-h</code>, </span><span class="term"><code class="option">--help</code></span><a class="headerlink" title="Permalink to this term" href="#-h">¶</a></dt><dd><p><a name="help-text"></a>Print a short help text and exit.
</p></dd><dt id="--version"><span class="term"><code class="option">--version</code></span><a class="headerlink" title="Permalink to this term" href="#--version">¶</a></dt><dd><p><a name="version-text"></a>Print a short version string and exit.</p></dd></dl></div></div><div class="refsect1"><a name="idm214189143952"></a><h2 id="Concepts">Concepts<a class="headerlink" title="Permalink to this headline" href="#Concepts">¶</a></h2><p>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
<a href="systemd.unit.html"><span class="citerefentry"><span class="refentrytitle">systemd.unit</span>(5)</span></a>,
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.</p><p>The following unit types are available:</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>Service units, which start and control
daemons and the processes they consist of. For
details see
<a href="systemd.service.html"><span class="citerefentry"><span class="refentrytitle">systemd.service</span>(5)</span></a>.</p></li><li class="listitem"><p>Socket units, which
encapsulate local IPC or network sockets in
the system, useful for socket-based
activation. For details about socket units see
<a href="systemd.socket.html"><span class="citerefentry"><span class="refentrytitle">systemd.socket</span>(5)</span></a>,
for details on socket-based activation and
other forms of activation, see
<a href="daemon.html"><span class="citerefentry"><span class="refentrytitle">daemon</span>(7)</span></a>.</p></li><li class="listitem"><p>Target units are useful to
group units, or provide well-known
synchronization points during boot-up, see
<a href="systemd.target.html"><span class="citerefentry"><span class="refentrytitle">systemd.target</span>(5)</span></a>.</p></li><li class="listitem"><p>Device units expose kernel
devices in systemd and may be used to
implement device-based activation. For details
see
<a href="systemd.device.html"><span class="citerefentry"><span class="refentrytitle">systemd.device</span>(5)</span></a>.</p></li><li class="listitem"><p>Mount units control mount
points in the file system, for details see
<a href="systemd.mount.html"><span class="citerefentry"><span class="refentrytitle">systemd.mount</span>(5)</span></a>.</p></li><li class="listitem"><p>Automount units provide
automount capabilities, for on-demand mounting
of file systems as well as parallelized
boot-up. See
<a href="systemd.automount.html"><span class="citerefentry"><span class="refentrytitle">systemd.automount</span>(5)</span></a>.</p></li><li class="listitem"><p>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
<a href="systemd.snapshot.html"><span class="citerefentry"><span class="refentrytitle">systemd.snapshot</span>(5)</span></a>.</p></li><li class="listitem"><p>Timer units are useful for
triggering activation of other units based on
timers. You may find details in
<a href="systemd.timer.html"><span class="citerefentry"><span class="refentrytitle">systemd.timer</span>(5)</span></a>.</p></li><li class="listitem"><p>Swap units are very similar to
mount units and encapsulate memory swap
partitions or files of the operating
system. They are described in <a href="systemd.swap.html"><span class="citerefentry"><span class="refentrytitle">systemd.swap</span>(5)</span></a>.</p></li><li class="listitem"><p>Path units may be used
to activate other services when file system
objects change or are modified. See
<a href="systemd.path.html"><span class="citerefentry"><span class="refentrytitle">systemd.path</span>(5)</span></a>.</p></li><li class="listitem"><p>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
<a href="systemd.slice.html"><span class="citerefentry"><span class="refentrytitle">systemd.slice</span>(5)</span></a>.</p></li><li class="listitem"><p>Scope units are similar to
service units, but manage foreign processes
instead of starting them as well. See
<a href="systemd.scope.html"><span class="citerefentry"><span class="refentrytitle">systemd.scope</span>(5)</span></a>.</p></li></ol></div><p>Units are named as their configuration
files. Some units have special semantics. A detailed
list is available in
<a href="systemd.special.html"><span class="citerefentry"><span class="refentrytitle">systemd.special</span>(7)</span></a>.</p><p>systemd knows various kinds of dependencies,
including positive and negative requirement
dependencies (i.e. <code class="varname">Requires=</code> and
<code class="varname">Conflicts=</code>) as well as ordering
dependencies (<code class="varname">After=</code> and
<code class="varname">Before=</code>). NB: ordering and
requirement dependencies are orthogonal. If only a
requirement dependency exists between two units
(e.g. <code class="filename">foo.service</code> requires
<code class="filename">bar.service</code>), but no ordering
dependency (e.g. <code class="filename">foo.service</code>
after <code class="filename">bar.service</code>) 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.</p><p>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.</p><p>On boot systemd activates the target unit
<code class="filename">default.target</code> 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
<code class="filename">graphical.target</code> (for
fully-featured boots into the UI) or
<code class="filename">multi-user.target</code> (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
<a href="systemd.special.html"><span class="citerefentry"><span class="refentrytitle">systemd.special</span>(7)</span></a>
for details about these target units.</p><p>Processes systemd spawns are placed in
individual Linux control groups named after the unit
which they belong to in the private systemd
hierarchy. (see <a class="ulink" href="https://www.kernel.org/doc/Documentation/cgroups/cgroups.txt" target="_top">cgroups.txt</a>
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
<code class="filename">/sys/fs/cgroup/systemd/</code>), or in tools
such as
<a href="ps.html"><span class="citerefentry"><span class="refentrytitle">ps</span>(1)</span></a>
(<span class="command"><strong>ps xawf -eo pid,user,cgroup,args</strong></span>
is particularly useful to list all processes and the
systemd units they belong to.).</p><p>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
<code class="filename">/dev/initctl</code> interface is
provided, and compatibility implementations of the
various SysV client tools are available. In addition to
that, various established Unix functionality such as
<code class="filename">/etc/fstab</code> or the
<code class="filename">utmp</code> database are
supported.</p><p>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.</p><p>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
<code class="filename">/sys</code> or
<code class="filename">/proc</code>.</p><p>For more information about the concepts and
ideas behind systemd, please refer to the <a class="ulink" href="http://0pointer.de/blog/projects/systemd.html" target="_top">Original
Design Document</a>.</p><p>Note that some but not all interfaces provided
by systemd are covered by the <a class="ulink" href="http://www.freedesktop.org/wiki/Software/systemd/InterfaceStabilityPromise" target="_top">Interface
Stability Promise</a>.</p><p>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 <a class="ulink" href="http://www.freedesktop.org/wiki/Software/systemd/Generators" target="_top">Generators
Specification</a>.</p><p>Systems which invoke systemd in a container
or initrd environment should implement the
<a class="ulink" href="http://www.freedesktop.org/wiki/Software/systemd/ContainerInterface" target="_top">Container
Interface</a> or <a class="ulink" href="http://www.freedesktop.org/wiki/Software/systemd/InitrdInterface" target="_top">initrd
Interface</a> specifications, respectively.</p></div><div class="refsect1"><a name="idm214189453632"></a><h2 id="Directories">Directories<a class="headerlink" title="Permalink to this headline" href="#Directories">¶</a></h2><div class="variablelist"><dl class="variablelist"><dt id="System unit directories"><span class="term">System unit directories</span><a class="headerlink" title="Permalink to this term" href="#System%20unit%20directories">¶</a></dt><dd><p>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
<span class="command"><strong>pkg-config systemd
--variable=systemdsystemunitdir</strong></span>. Other
directories checked are
<code class="filename">/usr/local/lib/systemd/system</code>
and
<code class="filename">/usr/lib/systemd/system</code>. User
configuration always takes
precedence. <span class="command"><strong>pkg-config
systemd
--variable=systemdsystemconfdir</strong></span>
returns the path of the system
configuration directory. Packages
should alter the content of these
directories only with the
<span class="command"><strong>enable</strong></span> and
<span class="command"><strong>disable</strong></span> commands of
the
<a href="systemctl.html"><span class="citerefentry"><span class="refentrytitle">systemctl</span>(1)</span></a>
tool. Full list of directories is provided in
<a href="systemd.unit.html"><span class="citerefentry"><span class="refentrytitle">systemd.unit</span>(5)</span></a>.
</p></dd></dl></div><div class="variablelist"><dl class="variablelist"><dt id="User unit directories"><span class="term">User unit directories</span><a class="headerlink" title="Permalink to this term" href="#User%20unit%20directories">¶</a></dt><dd><p>Similar rules apply
for the user unit
directories. However, here the <a class="ulink" href="http://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html" target="_top">XDG
Base Directory specification</a>
is followed to find
units. Applications should place their
unit files in the directory returned
by <span class="command"><strong>pkg-config systemd
--variable=systemduserunitdir</strong></span>. Global
configuration is done in the directory
reported by <span class="command"><strong>pkg-config
systemd
--variable=systemduserconfdir</strong></span>. The
<span class="command"><strong>enable</strong></span> and
<span class="command"><strong>disable</strong></span> commands of
the
<a href="systemctl.html"><span class="citerefentry"><span class="refentrytitle">systemctl</span>(1)</span></a>
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
<a href="systemd.unit.html"><span class="citerefentry"><span class="refentrytitle">systemd.unit</span>(5)</span></a>.
</p></dd></dl></div><div class="variablelist"><dl class="variablelist"><dt id="SysV init scripts directory"><span class="term">SysV init scripts directory</span><a class="headerlink" title="Permalink to this term" href="#SysV%20init%20scripts%20directory">¶</a></dt><dd><p>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
<code class="filename">.service</code> suffix
removed).</p></dd></dl></div><div class="variablelist"><dl class="variablelist"><dt id="SysV runlevel link farm directory"><span class="term">SysV runlevel link farm directory</span><a class="headerlink" title="Permalink to this term" href="#SysV%20runlevel%20link%20farm%20directory">¶</a></dt><dd><p>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.</p></dd></dl></div></div><div class="refsect1"><a name="idm214189693872"></a><h2 id="Signals">Signals<a class="headerlink" title="Permalink to this headline" href="#Signals">¶</a></h2><div class="variablelist"><dl class="variablelist"><dt id="SIGTERM"><span class="term"><code class="constant">SIGTERM</code></span><a class="headerlink" title="Permalink to this term" href="#SIGTERM">¶</a></dt><dd><p>Upon receiving this
signal the systemd system manager
serializes its state, reexecutes
itself and deserializes the saved
state again. This is mostly equivalent
to <span class="command"><strong>systemctl
daemon-reexec</strong></span>.</p><p>systemd user managers will
start the
<code class="filename">exit.target</code> unit
when this signal is received. This is
mostly equivalent to
<span class="command"><strong>systemctl --user start
exit.target</strong></span>.</p></dd><dt id="SIGINT"><span class="term"><code class="constant">SIGINT</code></span><a class="headerlink" title="Permalink to this term" href="#SIGINT">¶</a></dt><dd><p>Upon receiving this
signal the systemd system manager will
start the
<code class="filename">ctrl-alt-del.target</code> unit. This
is mostly equivalent to
<span class="command"><strong>systemctl start
ctl-alt-del.target</strong></span>.</p><p>systemd user managers
treat this signal the same way as
<code class="constant">SIGTERM</code>.</p></dd><dt id="SIGWINCH"><span class="term"><code class="constant">SIGWINCH</code></span><a class="headerlink" title="Permalink to this term" href="#SIGWINCH">¶</a></dt><dd><p>When this signal is
received the systemd system manager
will start the
<code class="filename">kbrequest.target</code>
unit. This is mostly equivalent to
<span class="command"><strong>systemctl start
kbrequest.target</strong></span>.</p><p>This signal is ignored by
systemd user
managers.</p></dd><dt id="SIGPWR"><span class="term"><code class="constant">SIGPWR</code></span><a class="headerlink" title="Permalink to this term" href="#SIGPWR">¶</a></dt><dd><p>When this signal is
received the systemd manager
will start the
<code class="filename">sigpwr.target</code>
unit. This is mostly equivalent to
<span class="command"><strong>systemctl start
sigpwr.target</strong></span>.</p></dd><dt id="SIGUSR1"><span class="term"><code class="constant">SIGUSR1</code></span><a class="headerlink" title="Permalink to this term" href="#SIGUSR1">¶</a></dt><dd><p>When this signal is
received the systemd manager will try
to reconnect to the D-Bus
bus.</p></dd><dt id="SIGUSR2"><span class="term"><code class="constant">SIGUSR2</code></span><a class="headerlink" title="Permalink to this term" href="#SIGUSR2">¶</a></dt><dd><p>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 <span class="command"><strong>systemctl
dump</strong></span>.</p></dd><dt id="SIGHUP"><span class="term"><code class="constant">SIGHUP</code></span><a class="headerlink" title="Permalink to this term" href="#SIGHUP">¶</a></dt><dd><p>Reloads the complete
daemon configuration. This is mostly
equivalent to <span class="command"><strong>systemctl
daemon-reload</strong></span>.</p></dd><dt id="SIGRTMIN+0"><span class="term"><code class="constant">SIGRTMIN+0</code></span><a class="headerlink" title="Permalink to this term" href="#SIGRTMIN+0">¶</a></dt><dd><p>Enters default mode, starts the
<code class="filename">default.target</code>
unit. This is mostly equivalent to
<span class="command"><strong>systemctl start
default.target</strong></span>.</p></dd><dt id="SIGRTMIN+1"><span class="term"><code class="constant">SIGRTMIN+1</code></span><a class="headerlink" title="Permalink to this term" href="#SIGRTMIN+1">¶</a></dt><dd><p>Enters rescue mode,
starts the
<code class="filename">rescue.target</code>
unit. This is mostly equivalent to
<span class="command"><strong>systemctl isolate
rescue.target</strong></span>.</p></dd><dt id="SIGRTMIN+2"><span class="term"><code class="constant">SIGRTMIN+2</code></span><a class="headerlink" title="Permalink to this term" href="#SIGRTMIN+2">¶</a></dt><dd><p>Enters emergency mode,
starts the
<code class="filename">emergency.service</code>
unit. This is mostly equivalent to
<span class="command"><strong>systemctl isolate
emergency.service</strong></span>.</p></dd><dt id="SIGRTMIN+3"><span class="term"><code class="constant">SIGRTMIN+3</code></span><a class="headerlink" title="Permalink to this term" href="#SIGRTMIN+3">¶</a></dt><dd><p>Halts the machine,
starts the
<code class="filename">halt.target</code>
unit. This is mostly equivalent to
<span class="command"><strong>systemctl start
halt.target</strong></span>.</p></dd><dt id="SIGRTMIN+4"><span class="term"><code class="constant">SIGRTMIN+4</code></span><a class="headerlink" title="Permalink to this term" href="#SIGRTMIN+4">¶</a></dt><dd><p>Powers off the machine,
starts the
<code class="filename">poweroff.target</code>
unit. This is mostly equivalent to
<span class="command"><strong>systemctl start
poweroff.target</strong></span>.</p></dd><dt id="SIGRTMIN+5"><span class="term"><code class="constant">SIGRTMIN+5</code></span><a class="headerlink" title="Permalink to this term" href="#SIGRTMIN+5">¶</a></dt><dd><p>Reboots the machine,
starts the
<code class="filename">reboot.target</code>
unit. This is mostly equivalent to
<span class="command"><strong>systemctl start
reboot.target</strong></span>.</p></dd><dt id="SIGRTMIN+6"><span class="term"><code class="constant">SIGRTMIN+6</code></span><a class="headerlink" title="Permalink to this term" href="#SIGRTMIN+6">¶</a></dt><dd><p>Reboots the machine via kexec,
starts the
<code class="filename">kexec.target</code>
unit. This is mostly equivalent to
<span class="command"><strong>systemctl start
kexec.target</strong></span>.</p></dd><dt id="SIGRTMIN+13"><span class="term"><code class="constant">SIGRTMIN+13</code></span><a class="headerlink" title="Permalink to this term" href="#SIGRTMIN+13">¶</a></dt><dd><p>Immediately halts the machine.</p></dd><dt id="SIGRTMIN+14"><span class="term"><code class="constant">SIGRTMIN+14</code></span><a class="headerlink" title="Permalink to this term" href="#SIGRTMIN+14">¶</a></dt><dd><p>Immediately powers off the machine.</p></dd><dt id="SIGRTMIN+15"><span class="term"><code class="constant">SIGRTMIN+15</code></span><a class="headerlink" title="Permalink to this term" href="#SIGRTMIN+15">¶</a></dt><dd><p>Immediately reboots the machine.</p></dd><dt id="SIGRTMIN+16"><span class="term"><code class="constant">SIGRTMIN+16</code></span><a class="headerlink" title="Permalink to this term" href="#SIGRTMIN+16">¶</a></dt><dd><p>Immediately reboots the machine with kexec.</p></dd><dt id="SIGRTMIN+20"><span class="term"><code class="constant">SIGRTMIN+20</code></span><a class="headerlink" title="Permalink to this term" href="#SIGRTMIN+20">¶</a></dt><dd><p>Enables display of
status messages on the console, as
controlled via
<code class="varname">systemd.show_status=1</code>
on the kernel command
line.</p></dd><dt id="SIGRTMIN+21"><span class="term"><code class="constant">SIGRTMIN+21</code></span><a class="headerlink" title="Permalink to this term" href="#SIGRTMIN+21">¶</a></dt><dd><p>Disables display of
status messages on the console, as
controlled via
<code class="varname">systemd.show_status=0</code>
on the kernel command
line.</p></dd><dt id="SIGRTMIN+22"><span class="term"><code class="constant">SIGRTMIN+22</code>, </span><span class="term"><code class="constant">SIGRTMIN+23</code></span><a class="headerlink" title="Permalink to this term" href="#SIGRTMIN+22">¶</a></dt><dd><p>Sets the log level to
"<code class="literal">debug</code>"
(or "<code class="literal">info</code>" on
<code class="constant">SIGRTMIN+23</code>), as
controlled via
<code class="varname">systemd.log_level=debug</code>
(or <code class="varname">systemd.log_level=info</code>
on <code class="constant">SIGRTMIN+23</code>) on
the kernel command
line.</p></dd><dt id="SIGRTMIN+24"><span class="term"><code class="constant">SIGRTMIN+24</code></span><a class="headerlink" title="Permalink to this term" href="#SIGRTMIN+24">¶</a></dt><dd><p>Immediately exits the
manager (only available for --user
instances).</p></dd><dt id="SIGRTMIN+26"><span class="term"><code class="constant">SIGRTMIN+26</code>, </span><span class="term"><code class="constant">SIGRTMIN+27</code>, </span><span class="term"><code class="constant">SIGRTMIN+28</code>, </span><span class="term"><code class="constant">SIGRTMIN+29</code></span><a class="headerlink" title="Permalink to this term" href="#SIGRTMIN+26">¶</a></dt><dd><p>Sets the log level to
"<code class="literal">journal-or-kmsg</code>"
(or "<code class="literal">console</code>" on
<code class="constant">SIGRTMIN+27</code>,
"<code class="literal">kmsg</code>" on
<code class="constant">SIGRTMIN+28</code>,
or "<code class="literal">syslog-or-kmsg</code>"
on <code class="constant">SIGRTMIN+29</code>), as
controlled via
<code class="varname">systemd.log_target=journal-or-kmsg</code>
(or <code class="varname">systemd.log_target=console</code>
on <code class="constant">SIGRTMIN+27</code>,
<code class="varname">systemd.log_target=kmsg</code>
on <code class="constant">SIGRTMIN+28</code>,
or
<code class="varname">systemd.log_target=syslog-or-kmsg</code>
on <code class="constant">SIGRTMIN+29</code>) on
the kernel command
line.</p></dd></dl></div></div><div class="refsect1"><a name="idm214191284560"></a><h2 id="Environment">Environment<a class="headerlink" title="Permalink to this headline" href="#Environment">¶</a></h2><div class="variablelist"><dl class="variablelist"><dt id="$SYSTEMD_LOG_LEVEL"><span class="term"><code class="varname">$SYSTEMD_LOG_LEVEL</code></span><a class="headerlink" title="Permalink to this term" href="#%24SYSTEMD_LOG_LEVEL">¶</a></dt><dd><p>systemd reads the
log level from this environment
variable. This can be overridden with
<code class="option">--log-level=</code>.</p></dd><dt id="$SYSTEMD_LOG_TARGET"><span class="term"><code class="varname">$SYSTEMD_LOG_TARGET</code></span><a class="headerlink" title="Permalink to this term" href="#%24SYSTEMD_LOG_TARGET">¶</a></dt><dd><p>systemd reads the
log target from this environment
variable. This can be overridden with
<code class="option">--log-target=</code>.</p></dd><dt id="$SYSTEMD_LOG_COLOR"><span class="term"><code class="varname">$SYSTEMD_LOG_COLOR</code></span><a class="headerlink" title="Permalink to this term" href="#%24SYSTEMD_LOG_COLOR">¶</a></dt><dd><p>Controls whether
systemd highlights important log
messages. This can be overridden with
<code class="option">--log-color=</code>.</p></dd><dt id="$SYSTEMD_LOG_LOCATION"><span class="term"><code class="varname">$SYSTEMD_LOG_LOCATION</code></span><a class="headerlink" title="Permalink to this term" href="#%24SYSTEMD_LOG_LOCATION">¶</a></dt><dd><p>Controls whether
systemd prints the code location along
with log messages. This can be
overridden with
<code class="option">--log-location=</code>.</p></dd><dt id="$XDG_CONFIG_HOME"><span class="term"><code class="varname">$XDG_CONFIG_HOME</code>, </span><span class="term"><code class="varname">$XDG_CONFIG_DIRS</code>, </span><span class="term"><code class="varname">$XDG_DATA_HOME</code>, </span><span class="term"><code class="varname">$XDG_DATA_DIRS</code></span><a class="headerlink" title="Permalink to this term" href="#%24XDG_CONFIG_HOME">¶</a></dt><dd><p>The systemd user
manager uses these variables in
accordance to the <a class="ulink" href="http://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html" target="_top">XDG
Base Directory specification</a>
to find its configuration.</p></dd><dt id="$SYSTEMD_UNIT_PATH"><span class="term"><code class="varname">$SYSTEMD_UNIT_PATH</code></span><a class="headerlink" title="Permalink to this term" href="#%24SYSTEMD_UNIT_PATH">¶</a></dt><dd><p>Controls where systemd
looks for unit
files.</p></dd><dt id="$SYSTEMD_SYSVINIT_PATH"><span class="term"><code class="varname">$SYSTEMD_SYSVINIT_PATH</code></span><a class="headerlink" title="Permalink to this term" href="#%24SYSTEMD_SYSVINIT_PATH">¶</a></dt><dd><p>Controls where systemd
looks for SysV init scripts.</p></dd><dt id="$SYSTEMD_SYSVRCND_PATH"><span class="term"><code class="varname">$SYSTEMD_SYSVRCND_PATH</code></span><a class="headerlink" title="Permalink to this term" href="#%24SYSTEMD_SYSVRCND_PATH">¶</a></dt><dd><p>Controls where systemd
looks for SysV init script runlevel link
farms.</p></dd><dt id="$LISTEN_PID"><span class="term"><code class="varname">$LISTEN_PID</code>, </span><span class="term"><code class="varname">$LISTEN_FDS</code></span><a class="headerlink" title="Permalink to this term" href="#%24LISTEN_PID">¶</a></dt><dd><p>Set by systemd for
supervised processes during
socket-based activation. See
<a href="sd_listen_fds.html"><span class="citerefentry"><span class="refentrytitle">sd_listen_fds</span>(3)</span></a>
for more information.
</p></dd><dt id="$NOTIFY_SOCKET"><span class="term"><code class="varname">$NOTIFY_SOCKET</code></span><a class="headerlink" title="Permalink to this term" href="#%24NOTIFY_SOCKET">¶</a></dt><dd><p>Set by systemd for
supervised processes for status and
start-up completion notification. See
<a href="sd_notify.html"><span class="citerefentry"><span class="refentrytitle">sd_notify</span>(3)</span></a>
for more information.
</p></dd></dl></div></div><div class="refsect1"><a name="idm214191260432"></a><h2 id="Kernel Command Line">Kernel Command Line<a class="headerlink" title="Permalink to this headline" href="#Kernel%20Command%20Line">¶</a></h2><p>When run as system instance systemd parses a
number of kernel command line
arguments<a href="#ftn.idm214191259376" class="footnote" name="idm214191259376"><sup class="footnote">[1]</sup></a>:</p><div class="variablelist"><dl class="variablelist"><dt id="systemd.unit="><span class="term"><code class="varname">systemd.unit=</code>, </span><span class="term"><code class="varname">rd.systemd.unit=</code></span><a class="headerlink" title="Permalink to this term" href="#systemd.unit=">¶</a></dt><dd><p>Overrides the unit to
activate on boot. Defaults to
<code class="filename">default.target</code>. This
may be used to temporarily boot into a
different boot unit, for example
<code class="filename">rescue.target</code> or
<code class="filename">emergency.service</code>. See
<a href="systemd.special.html"><span class="citerefentry"><span class="refentrytitle">systemd.special</span>(7)</span></a>
for details about these units. The
option prefixed with
"<code class="literal">rd.</code>" is honored
only in the initial RAM disk (initrd),
while the one that is not prefixed only
in the main system.</p></dd><dt id="systemd.dump_core="><span class="term"><code class="varname">systemd.dump_core=</code></span><a class="headerlink" title="Permalink to this term" href="#systemd.dump_core=">¶</a></dt><dd><p>Takes a boolean
argument. If <code class="option">true</code>,
systemd dumps core when it
crashes. Otherwise, no core dump is
created. Defaults to
<code class="option">true</code>.</p></dd><dt id="systemd.crash_shell="><span class="term"><code class="varname">systemd.crash_shell=</code></span><a class="headerlink" title="Permalink to this term" href="#systemd.crash_shell=">¶</a></dt><dd><p>Takes a boolean
argument. If <code class="option">true</code>,
systemd spawns a shell when it
crashes. Otherwise, no shell is
spawned. Defaults to
<code class="option">false</code>, for security
reasons, as the shell is not protected
by any password
authentication.</p></dd><dt id="systemd.crash_chvt="><span class="term"><code class="varname">systemd.crash_chvt=</code></span><a class="headerlink" title="Permalink to this term" href="#systemd.crash_chvt=">¶</a></dt><dd><p>Takes an integer
argument. If positive systemd
activates the specified virtual
terminal when it crashes. Defaults to
<code class="constant">-1</code>.</p></dd><dt id="systemd.confirm_spawn="><span class="term"><code class="varname">systemd.confirm_spawn=</code></span><a class="headerlink" title="Permalink to this term" href="#systemd.confirm_spawn=">¶</a></dt><dd><p>Takes a boolean
argument. If <code class="option">true</code>,
asks for confirmation when spawning
processes. Defaults to
<code class="option">false</code>.</p></dd><dt id="systemd.show_status="><span class="term"><code class="varname">systemd.show_status=</code></span><a class="headerlink" title="Permalink to this term" href="#systemd.show_status=">¶</a></dt><dd><p>Takes a boolean
argument or the constant
<code class="constant">auto</code>. If
<code class="option">true</code>, shows terse
service status updates on the console
during bootup.
<code class="constant">auto</code> behaves like
<code class="option">false</code> until a service
fails or there is a significant delay
in boot. Defaults to
<code class="option">true</code>, unless
<code class="option">quiet</code> is passed as
kernel command line option in which
case it defaults to
<code class="constant">auto</code>.</p></dd><dt id="systemd.log_target="><span class="term"><code class="varname">systemd.log_target=</code>, </span><span class="term"><code class="varname">systemd.log_level=</code>, </span><span class="term"><code class="varname">systemd.log_color=</code>, </span><span class="term"><code class="varname">systemd.log_location=</code></span><a class="headerlink" title="Permalink to this term" href="#systemd.log_target=">¶</a></dt><dd><p>Controls log output,
with the same effect as the
<code class="varname">$SYSTEMD_LOG_TARGET</code>, <code class="varname">$SYSTEMD_LOG_LEVEL</code>, <code class="varname">$SYSTEMD_LOG_COLOR</code>, <code class="varname">$SYSTEMD_LOG_LOCATION</code>
environment variables described above.</p></dd><dt id="systemd.default_standard_output="><span class="term"><code class="varname">systemd.default_standard_output=</code>, </span><span class="term"><code class="varname">systemd.default_standard_error=</code></span><a class="headerlink" title="Permalink to this term" href="#systemd.default_standard_output=">¶</a></dt><dd><p>Controls default
standard output and error output for
services, with the same effect as the
<code class="option">--default-standard-output=</code>
and <code class="option">--default-standard-error=</code>
command line arguments described
above, respectively.</p></dd><dt id="systemd.setenv="><span class="term"><code class="varname">systemd.setenv=</code></span><a class="headerlink" title="Permalink to this term" href="#systemd.setenv=">¶</a></dt><dd><p>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.</p></dd><dt id="quiet"><span class="term"><code class="varname">quiet</code></span><a class="headerlink" title="Permalink to this term" href="#quiet">¶</a></dt><dd><p>Turn off
status output at boot, much like
<code class="varname">systemd.show_status=false</code>
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.
</p></dd><dt id="debug"><span class="term"><code class="varname">debug</code></span><a class="headerlink" title="Permalink to this term" href="#debug">¶</a></dt><dd><p>Turn on debugging
output. This is equivalent to
<code class="varname">systemd.log_level=debug</code>.
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.</p></dd><dt id="-b"><span class="term"><code class="varname">-b</code>, </span><span class="term"><code class="varname">emergency</code></span><a class="headerlink" title="Permalink to this term" href="#-b">¶</a></dt><dd><p>Boot into emergency
mode. This is equivalent to
<code class="varname">systemd.unit=emergency.target</code>
and provided for compatibility
reasons and to be easier to type.</p></dd><dt id="single"><span class="term"><code class="varname">single</code>, </span><span class="term"><code class="varname">s</code>, </span><span class="term"><code class="varname">S</code>, </span><span class="term"><code class="varname">1</code></span><a class="headerlink" title="Permalink to this term" href="#single">¶</a></dt><dd><p>Boot into rescue
mode. This is equivalent to
<code class="varname">systemd.unit=rescue.target</code>
and provided for compatibility reasons
and to be easier to
type.</p></dd><dt id="2"><span class="term"><code class="varname">2</code>, </span><span class="term"><code class="varname">3</code>, </span><span class="term"><code class="varname">4</code>, </span><span class="term"><code class="varname">5</code></span><a class="headerlink" title="Permalink to this term" href="#2">¶</a></dt><dd><p>Boot into the
specified legacy SysV runlevel. These
are equivalent to
<code class="varname">systemd.unit=runlevel2.target</code>,
<code class="varname">systemd.unit=runlevel3.target</code>,
<code class="varname">systemd.unit=runlevel4.target</code>,
and <code class="varname">systemd.unit=runlevel5.target</code>, respectively,
and provided for compatibility reasons
and to be easier to
type.</p></dd><dt id="locale.LANG="><span class="term"><code class="varname">locale.LANG=</code>, </span><span class="term"><code class="varname">locale.LANGUAGE=</code>, </span><span class="term"><code class="varname">locale.LC_CTYPE=</code>, </span><span class="term"><code class="varname">locale.LC_NUMERIC=</code>, </span><span class="term"><code class="varname">locale.LC_TIME=</code>, </span><span class="term"><code class="varname">locale.LC_COLLATE=</code>, </span><span class="term"><code class="varname">locale.LC_MONETARY=</code>, </span><span class="term"><code class="varname">locale.LC_MESSAGES=</code>, </span><span class="term"><code class="varname">locale.LC_PAPER=</code>, </span><span class="term"><code class="varname">locale.LC_NAME=</code>, </span><span class="term"><code class="varname">locale.LC_ADDRESS=</code>, </span><span class="term"><code class="varname">locale.LC_TELEPHONE=</code>, </span><span class="term"><code class="varname">locale.LC_MEASUREMENT=</code>, </span><span class="term"><code class="varname">locale.LC_IDENTIFICATION=</code></span><a class="headerlink" title="Permalink to this term" href="#locale.LANG=">¶</a></dt><dd><p>Set the system locale
to use. This overrides the settings in
<code class="filename">/etc/locale.conf</code>. For
more information see
<a href="locale.conf.html"><span class="citerefentry"><span class="refentrytitle">locale.conf</span>(5)</span></a>
and
<a href="locale.html"><span class="citerefentry"><span class="refentrytitle">locale</span>(7)</span></a>.
</p></dd></dl></div><p>For other kernel command line parameters
understood by components of the core OS, please refer
to
<a href="kernel-command-line.html"><span class="citerefentry"><span class="refentrytitle">kernel-command-line</span>(7)</span></a>.</p></div><div class="refsect1"><a name="idm214187977552"></a><h2 id="Sockets and FIFOs">Sockets and FIFOs<a class="headerlink" title="Permalink to this headline" href="#Sockets%20and%20FIFOs">¶</a></h2><div class="variablelist"><dl class="variablelist"><dt id="/run/systemd/notify"><span class="term"><code class="filename">/run/systemd/notify</code></span><a class="headerlink" title="Permalink to this term" href="#/run/systemd/notify">¶</a></dt><dd><p>Daemon status
notification socket. This is an
<code class="constant">AF_UNIX</code> datagram socket and is used to
implement the daemon notification
logic as implemented by
<a href="sd_notify.html"><span class="citerefentry"><span class="refentrytitle">sd_notify</span>(3)</span></a>.</p></dd><dt id="/run/systemd/shutdownd"><span class="term"><code class="filename">/run/systemd/shutdownd</code></span><a class="headerlink" title="Permalink to this term" href="#/run/systemd/shutdownd">¶</a></dt><dd><p>Used internally by the
<a href="shutdown.html"><span class="citerefentry"><span class="refentrytitle">shutdown</span>(8)</span></a>
tool to implement delayed
shutdowns. This is an <code class="constant">AF_UNIX</code> datagram
socket.</p></dd><dt id="/run/systemd/private"><span class="term"><code class="filename">/run/systemd/private</code></span><a class="headerlink" title="Permalink to this term" href="#/run/systemd/private">¶</a></dt><dd><p>Used internally as
communication channel between
<a href="systemctl.html"><span class="citerefentry"><span class="refentrytitle">systemctl</span>(1)</span></a>
and the systemd process. This is an
<code class="constant">AF_UNIX</code> stream socket. This interface
is private to systemd and should not
be used in external
projects.</p></dd><dt id="/dev/initctl"><span class="term"><code class="filename">/dev/initctl</code></span><a class="headerlink" title="Permalink to this term" href="#/dev/initctl">¶</a></dt><dd><p>Limited compatibility
support for the SysV client interface,
as implemented by the
<code class="filename">systemd-initctl.service</code>
unit. This is a named pipe in the file
system. This interface is obsolete and
should not be used in new
applications.</p></dd></dl></div></div><div class="refsect1"><a name="idm214187964368"></a><h2 id="See Also">See Also<a class="headerlink" title="Permalink to this headline" href="#See%20Also">¶</a></h2><p>
The <a class="ulink" href="http://www.freedesktop.org/wiki/Software/systemd/" target="_top">systemd Homepage</a>,
<a href="systemd-system.conf.html"><span class="citerefentry"><span class="refentrytitle">systemd-system.conf</span>(5)</span></a>,
<a href="locale.conf.html"><span class="citerefentry"><span class="refentrytitle">locale.conf</span>(5)</span></a>,
<a href="systemctl.html"><span class="citerefentry"><span class="refentrytitle">systemctl</span>(1)</span></a>,
<a href="journalctl.html"><span class="citerefentry"><span class="refentrytitle">journalctl</span>(1)</span></a>,
<a href="systemd-notify.html"><span class="citerefentry"><span class="refentrytitle">systemd-notify</span>(1)</span></a>,
<a href="daemon.html"><span class="citerefentry"><span class="refentrytitle">daemon</span>(7)</span></a>,
<a href="sd-daemon.html"><span class="citerefentry"><span class="refentrytitle">sd-daemon</span>(3)</span></a>,
<a href="systemd.unit.html"><span class="citerefentry"><span class="refentrytitle">systemd.unit</span>(5)</span></a>,
<a href="systemd.special.html"><span class="citerefentry"><span class="refentrytitle">systemd.special</span>(5)</span></a>,
<a href="pkg-config.html"><span class="citerefentry"><span class="refentrytitle">pkg-config</span>(1)</span></a>,
<a href="kernel-command-line.html"><span class="citerefentry"><span class="refentrytitle">kernel-command-line</span>(7)</span></a>,
<a href="bootup.html"><span class="citerefentry"><span class="refentrytitle">bootup</span>(7)</span></a>,
<a href="systemd.directives.html"><span class="citerefentry"><span class="refentrytitle">systemd.directives</span>(7)</span></a>
</p></div><div class="footnotes"><br><hr style="width:100; text-align:left;margin-left: 0"><div id="ftn.idm214191259376" class="footnote"><p><a href="#idm214191259376" class="para"><sup class="para">[1] </sup></a>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
<code class="filename">/proc/cmdline</code>
instead.</p></div></div></div></body></html>
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