are mostly equivalent when invoked from normal login sessions. See
<citerefentry><refentrytitle>telinit</refentrytitle><manvolnum>8</manvolnum></citerefentry>
for more information.</para>
+
+ <para>When run as system instance, systemd interprets
+ the configuration file
+ <filename>system.conf</filename>, otherwise
+ <filename>session.conf</filename>. See
+ <citerefentry><refentrytitle>systemd.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>
+ for more information.</para>
</refsect1>
<refsect1>
<listitem><para>Prints a short help
text and exits.</para></listitem>
</varlistentry>
+ <varlistentry>
+ <term><option>--test</option></term>
+
+ <listitem><para>Determine startup
+ sequence, dump it and exit. This is an
+ option useful for debugging
+ only.</para></listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><option>--dump-configuration-items</option></term>
+
+ <listitem><para>Dump understood unit
+ configuration items. This outputs a
+ terse but complete list of
+ configuration items understood in unit
+ definition files.</para></listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><option>--introspect=</option></term>
+
+ <listitem><para>Extract D-Bus
+ interface introspection data. This is
+ mostly useful at install time
+ to generate data suitable for the
+ D-Bus interfaces
+ repository. Optionally the interface
+ name for the introspection data may be
+ specified. If omitted, the
+ introspection data for all interfaces
+ is dumped.</para></listitem>
+ </varlistentry>
<varlistentry>
<term><option>--unit=</option></term>
debugging.</para></listitem>
</varlistentry>
<varlistentry>
- <term><option>--test</option></term>
+ <term><option>--dump-core</option></term>
- <listitem><para>Determine startup
- sequence, dump it and exit. This is an
- option useful for debugging
- only.</para></listitem>
+ <listitem><para>Dump core on crash. This switch has no effect when run as session instance.</para></listitem>
</varlistentry>
<varlistentry>
- <term><option>--dump-configuration-items</option></term>
+ <term><option>--crash-shell</option></term>
- <listitem><para>Dump understood unit
- configuration items. This outputs a
- terse but complete list of
- configuration items understood in unit
- definition files.</para></listitem>
+ <listitem><para>Run shell on crash. This switch has no effect when run as session instance.</para></listitem>
</varlistentry>
<varlistentry>
<term><option>--confirm-spawn</option></term>
- <listitem><para>Ask for confirmation when spawning processes.</para></listitem>
+ <listitem><para>Ask for confirmation when spawning processes. This switch has no effect when run as session instance.</para></listitem>
</varlistentry>
<varlistentry>
- <term><option>--introspect=</option></term>
+ <term><option>--show-status</option></term>
- <listitem><para>Extract D-Bus
- interface introspection data. This is
- mostly useful at build at install time
- to generate data suitable for the
- D-Bus interfaces
- repository. Optionally the interface
- name for the introspection data may be
- specified. If omitted, the
- introspection data for all interfaces
- is dumped.</para></listitem>
+ <listitem><para>Show terse service status information while booting. This switch has no effect when run as session instance.</para></listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><option>--log-target=</option></term>
+
+ <listitem><para>Set log
+ target. Argument must be one of
+ <option>console</option>,
+ <option>syslog</option>,
+ <option>kmsg</option>,
+ <option>syslog-or-kmsg</option>,
+ <option>null</option>.</para></listitem>
</varlistentry>
<varlistentry>
<term><option>--log-level=</option></term>
<option>info</option>,
<option>debug</option>.</para></listitem>
</varlistentry>
- <varlistentry>
- <term><option>--log-target=</option></term>
-
- <listitem><para>Set log
- target. Argument must be one of
- <option>console</option>,
- <option>syslog</option>,
- <option>kmsg</option>,
- <option>syslog-or-kmsg</option>,
- <option>null</option>.</para></listitem>
- </varlistentry>
<varlistentry>
<term><option>--log-color=</option></term>
configuration or dynamically from system state. Units
may be active (meaning started, bound, plugged in, ...
depending on the unit type), or inactive (meaning
- stopped, unbound, unplugged, ...), as well is in the
+ stopped, unbound, unplugged, ...), as well as in the
process of being activated or deactivated,
i.e. between the two states. The following unit types
are available:</para>
systemd. They are described in <citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem>
<listitem><para>Path units may be used
- activate other services when file system
+ to activate other services when file system
objects change or are modified. See
<citerefentry><refentrytitle>systemd.path</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem>
<citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para>
<para>On boot systemd activates the target unit
- <filename>default.target</filename> whose job it is to
+ <filename>default.target</filename> 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
<citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry>
for details about these target units.</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="http://www.kernel.org/doc/Documentation/cgroups/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 via the
+ file system hierarchy (beneath
+ <filename>/cgroup/systemd/</filename>), or in tools
+ such as
+ <citerefentry><refentrytitle>ps</refentrytitle><manvolnum>1</manvolnum></citerefentry>
+ (<command>ps xawf -eo pid,user,cgroup,args</command>
+ is particularly useful to list all processes and the
+ systemd units they belong to.).</para>
+
+ <para>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
+ <filename>/dev/initctl</filename> interface is
+ provided, and compatibility implementations of the
+ various SysV client tools are available. In addition to
+ that, various established Unix functionality such as
+ <filename>/etc/fstab</filename> or the
+ <filename>utmp</filename> database are
+ supported.</para>
+
+ <para>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.</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 host name or
+ configures the loopback network device. It also sets
+ up and mounts various API file systems, such as
+ <filename>/sys</filename> or
+ <filename>/proc</filename>.</para>
+
<para>For more information about the concepts and
ideas behind systemd please refer to the <ulink
url="http://0pointer.de/blog/projects/systemd.html">Original
- Announcement Document</ulink>.</para>
+ Design Document</ulink>.</para>
</refsect1>
<refsect1>
</variablelist>
</refsect1>
+ <refsect1>
+ <title>Kernel Command Line</title>
+
+ <para>When run as system instance systemd parses a few kernel command line arguments:</para>
+
+ <variablelist>
+ <varlistentry>
+ <term><varname>systemd.unit=</varname></term>
+
+ <listitem><para>Overrides the unit to
+ activate on boot. Defaults to
+ <filename>default.target</filename>. This
+ may be used to temporarily boot into a
+ different boot unit, for example
+ <filename>rescue.target</filename> or
+ <filename>emergency.service</filename>. See
+ <citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry>
+ for details about these
+ units.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>systemd.log_target=</varname></term>
+ <term><varname>systemd.log_level=</varname></term>
+ <term><varname>systemd.log_color=</varname></term>
+ <term><varname>systemd.log_location=</varname></term>
+
+ <listitem><para>Controls log output,
+ with the same effect as the
+ <varname>$SYSTEMD_LOG_TARGET</varname>, <varname>$SYSTEMD_LOG_LEVEL</varname>, <varname>$SYSTEMD_LOG_COLOR</varname>, <varname>$SYSTEMD_LOG_LOCATION</varname>
+ environment variables described above.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>systemd.dump_core=</varname></term>
+
+ <listitem><para>Takes a boolean
+ argument. If <option>true</option>
+ systemd dumps core when it
+ crashes. Otherwise no core dump is
+ created. Defaults to
+ <option>true</option>.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>systemd.crash_shell=</varname></term>
+
+ <listitem><para>Takes a boolean
+ argument. If <option>true</option>
+ systemd spawns a shell when it
+ crashes. Otherwise no core dump is
+ created. Defaults to
+ <option>false</option>, for security
+ reasons, as the shell is not protected
+ by any password
+ authentication.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>systemd.crash_chvt=</varname></term>
+
+ <listitem><para>Takes an integer
+ argument. If positive systemd
+ activates the specified virtual
+ terminal when it crashes. Defaults to
+ <literal>-1</literal>.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>systemd.show_status=</varname></term>
+
+ <listitem><para>Takes a boolean
+ argument. If <option>true</option>
+ shows terse service status updates on
+ the console during bootup. Defaults to
+ <option>true</option>.</para></listitem>
+ </varlistentry>
+
+ </variablelist>
+ </refsect1>
+
<refsect1>
<title>Sockets and FIFOs</title>
~ianmdlvl / elogind.git / blobdiff