| <?xml version='1.0'?> <!--*-nxml-*--> |
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| Copyright 2010 Lennart Poettering |
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| |
| <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> |
| <refentrytitle>systemd</refentrytitle> |
| <manvolnum>1</manvolnum> |
| </refmeta> |
| |
| <refnamediv> |
| <refname>systemd</refname> |
| <refname>init</refname> |
| <refpurpose>systemd System and Service Manager</refpurpose> |
| </refnamediv> |
| |
| <refsynopsisdiv> |
| <cmdsynopsis> |
| <command>systemd <arg choice="opt" rep="repeat">OPTIONS</arg></command> |
| </cmdsynopsis> |
| <cmdsynopsis> |
| <command>init <arg choice="opt" rep="repeat">OPTIONS</arg> <arg choice="req">COMMAND</arg></command> |
| </cmdsynopsis> |
| </refsynopsisdiv> |
| |
| <refsect1> |
| <title>Description</title> |
| |
| <para>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.</para> |
| |
| <para>For compatibility with SysV, if systemd is called |
| as <command>init</command> and a PID that is not |
| 1, it will execute <command>telinit</command> and pass |
| all command line arguments unmodified. That means |
| <command>init</command> and <command>telinit</command> |
| 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>user.conf</filename>. See |
| <citerefentry><refentrytitle>systemd.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry> |
| for more information.</para> |
| </refsect1> |
| |
| <refsect1> |
| <title>Options</title> |
| |
| <para>The following options are understood:</para> |
| |
| <variablelist> |
| <varlistentry> |
| <term><option>-h</option></term> |
| <term><option>--help</option></term> |
| |
| <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> |
| |
| <listitem><para>Set default unit to |
| activate on startup. If not specified |
| defaults to |
| <filename>default.target</filename>.</para></listitem> |
| </varlistentry> |
| <varlistentry> |
| <term><option>--system</option></term> |
| <term><option>--user</option></term> |
| |
| <listitem><para>Tell systemd to run a |
| system instance (resp. user |
| instance), even if the process ID is |
| not 1 (resp. is 1), i.e. systemd is |
| not (resp. is) run as init process. |
| 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 <option>--system</option> |
| mode, but PID not 1. In practice, |
| passing <option>--system</option> explicitly is |
| only useful in conjunction with |
| <option>--test</option>.</para></listitem> |
| </varlistentry> |
| <varlistentry> |
| <term><option>--dump-core</option></term> |
| |
| <listitem><para>Dump core on |
| crash. This switch has no effect when |
| run as user |
| instance.</para></listitem> |
| </varlistentry> |
| <varlistentry> |
| <term><option>--crash-shell</option></term> |
| |
| <listitem><para>Run shell on |
| crash. This switch has no effect when |
| run as user |
| instance.</para></listitem> |
| </varlistentry> |
| <varlistentry> |
| <term><option>--confirm-spawn</option></term> |
| |
| <listitem><para>Ask for confirmation |
| when spawning processes. This switch |
| has no effect when run as user |
| instance.</para></listitem> |
| </varlistentry> |
| <varlistentry> |
| <term><option>--show-status=</option></term> |
| |
| <listitem><para>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 |
| <option>true</option>.</para></listitem> |
| </varlistentry> |
| <varlistentry> |
| <term><option>--sysv-console=</option></term> |
| |
| <listitem><para>Controls whether |
| output of SysV init scripts will be |
| directed to the console. This switch |
| has no effect when run as user |
| instance. Takes a boolean argument |
| which may be omitted which is |
| interpreted as |
| <option>true</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-level=</option></term> |
| |
| <listitem><para>Set log level. As |
| argument this accepts a numerical log |
| level or the well-known <citerefentry><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry> |
| symbolic names (lowercase): |
| <option>emerg</option>, |
| <option>alert</option>, |
| <option>crit</option>, |
| <option>err</option>, |
| <option>warning</option>, |
| <option>notice</option>, |
| <option>info</option>, |
| <option>debug</option>.</para></listitem> |
| </varlistentry> |
| <varlistentry> |
| <term><option>--log-color=</option></term> |
| |
| <listitem><para>Highlight important |
| log messages. Argument is a boolean |
| value. If the argument is omitted it |
| defaults to |
| <option>true</option>.</para></listitem> |
| </varlistentry> |
| <varlistentry> |
| <term><option>--log-location=</option></term> |
| |
| <listitem><para>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 |
| <option>true</option>.</para></listitem> |
| </varlistentry> |
| <varlistentry> |
| <term><option>--default-standard-output=</option></term> |
| <term><option>--default-standard-error=</option></term> |
| |
| <listitem><para>Sets the default |
| output resp. error output for all |
| services and sockets, i.e. controls |
| the default for |
| <option>StandardOutput=</option> |
| resp. <option>StandardExecute=</option> |
| (see |
| <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry> |
| for details). Takes one of |
| <option>inherit</option>, |
| <option>null</option>, |
| <option>tty</option>, |
| <option>syslog</option>, |
| <option>syslog+console</option>, |
| <option>kmsg</option>, |
| <option>kmsg-console</option>. If the |
| argument is omitted it defaults to |
| <option>inherit</option>.</para></listitem> |
| </varlistentry> |
| </variablelist> |
| </refsect1> |
| |
| <refsect1> |
| <title>Concepts</title> |
| |
| <para>systemd provides a dependency system between |
| various entities called "units". 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 |
| <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>, |
| however some are created automatically from other |
| configuration or dynamically from system state. 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.</para> |
| |
| <para>The following unit types are available:</para> |
| |
| <orderedlist> |
| <listitem><para>Service units, which control |
| daemons and the processes they consist of. For |
| details see |
| <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem> |
| |
| <listitem><para>Socket units, which |
| encapsulate local IPC or network sockets in |
| the system, useful for socket-based |
| activation. For details about socket units see |
| <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>, |
| for details on socket-based activation and |
| other forms of activation, see |
| <citerefentry><refentrytitle>daemon</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para></listitem> |
| |
| <listitem><para>Target units are useful to |
| group units, or provide well-known |
| synchronization points during boot-up, see |
| <citerefentry><refentrytitle>systemd.target</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem> |
| |
| <listitem><para>Device units expose kernel |
| devices in systemd and may be used to |
| implement device-based activation. For details |
| see |
| <citerefentry><refentrytitle>systemd.device</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem> |
| |
| <listitem><para>Mount units control mount |
| points in the file system, for details see |
| <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem> |
| |
| <listitem><para>Automount units provide |
| automount capabilities, for on-demand mounting |
| of file systems as well as parallelized |
| boot-up. See |
| <citerefentry><refentrytitle>systemd.automount</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem> |
| |
| <listitem><para>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 |
| <citerefentry><refentrytitle>systemd.snapshot</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem> |
| |
| <listitem><para>Timer units are useful for |
| triggering activation of other units based on |
| timers. You may find details in |
| <citerefentry><refentrytitle>systemd.timer</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem> |
| |
| <listitem><para>Swap units are very similar to |
| mount units and encapsulate memory swap |
| partitions or files of the operating |
| system. They are described in <citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem> |
| |
| <listitem><para>Path units may be used |
| to activate other services when file system |
| objects change or are modified. See |
| <citerefentry><refentrytitle>systemd.path</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem> |
| |
| </orderedlist> |
| |
| <para>Units are named as their configuration |
| files. Some units have special semantics. A detailed |
| list is available in |
| <citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para> |
| |
| <para>systemd knows various kinds of dependencies, |
| including positive and negative requirement |
| dependencies (i.e. <varname>Requires=</varname> and |
| <varname>Conflicts=</varname>) as well as ordering |
| dependencies (<varname>After=</varname> and |
| <varname>Before=</varname>). NB: ordering and |
| requirement dependencies are orthogonal. If only a |
| requirement dependency exists between two units |
| (e.g. <filename>foo.service</filename> requires |
| <filename>bar.service</filename>), but no ordering |
| dependency (e.g. <filename>foo.service</filename> |
| after <filename>bar.service</filename>) 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.</para> |
| |
| <para>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.</para> |
| |
| <para>On boot systemd activates the target unit |
| <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 |
| <filename>graphical.target</filename> (for |
| fully-featured boots into the UI) or |
| <filename>multi-user.target</filename> (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 |
| <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>/sys/fs/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 |
| Design Document</ulink>.</para> |
| |
| <para>Note that some but not all interfaces provided |
| by systemd are covered by the <ulink |
| url="http://www.freedesktop.org/wiki/Software/systemd/InterfaceStabilityPromise">Interface |
| Stability Promise</ulink>.</para> |
| </refsect1> |
| |
| <refsect1> |
| <title>Directories</title> |
| |
| <variablelist> |
| <varlistentry> |
| <term>System unit directories</term> |
| |
| <listitem><para>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 |
| <command>pkg-config systemd |
| --variable=systemdsystemunitdir</command>. Other |
| directories checked are |
| <filename>/usr/local/share/systemd/system</filename> |
| and |
| <filename>/usr/share/systemd/system</filename>. User |
| configuration always takes |
| precedence. <command>pkg-config |
| systemd |
| --variable=systemdsystemconfdir</command> |
| returns the path of the system |
| configuration directory. Packages |
| should alter the content of these |
| directories only with the |
| <command>enable</command> and |
| <command>disable</command> commands of |
| the |
| <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry> |
| tool.</para></listitem> |
| </varlistentry> |
| </variablelist> |
| |
| <variablelist> |
| <varlistentry> |
| <term>User unit directories</term> |
| |
| <listitem><para>Similar rules apply |
| for the user unit |
| directories. However, here the <ulink |
| url="http://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html">XDG |
| Base Directory specification</ulink> |
| is followed to find |
| units. Applications should place their |
| unit files in the directory returned |
| by <command>pkg-config systemd |
| --variable=systemduserunitdir</command>. Global |
| configuration is done in the directory |
| reported by <command>pkg-config |
| systemd |
| --variable=systemduserconfdir</command>. The |
| <command>enable</command> and |
| <command>disable</command> commands of |
| the |
| <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry> |
| tool can handle both global (i.e. for |
| all users) and private (for one user) |
| enabling/disabling of |
| units.</para></listitem> |
| </varlistentry> |
| </variablelist> |
| |
| <variablelist> |
| <varlistentry> |
| <term>SysV init scripts directory</term> |
| |
| <listitem><para>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 |
| <filename>.service</filename> suffix |
| removed).</para></listitem> |
| </varlistentry> |
| </variablelist> |
| |
| <variablelist> |
| <varlistentry> |
| <term>SysV runlevel link farm directory</term> |
| |
| <listitem><para>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.</para></listitem> |
| </varlistentry> |
| </variablelist> |
| </refsect1> |
| |
| <refsect1> |
| <title>Signals</title> |
| |
| <variablelist> |
| <varlistentry> |
| <term>SIGTERM</term> |
| |
| <listitem><para>Upon receiving this |
| signal the systemd system manager |
| serializes its state, reexecutes |
| itself and deserializes the saved |
| state again. This is mostly equivalent |
| to <command>systemctl |
| daemon-reexec</command>.</para> |
| |
| <para>systemd user managers will |
| start the |
| <filename>exit.target</filename> unit |
| when this signal is received. This is |
| mostly equivalent to |
| <command>systemctl --user start |
| exit.target</command>.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term>SIGINT</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</command>.</para> |
| |
| <para>systemd user managers |
| treat this signal the same way as |
| SIGTERM.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term>SIGWINCH</term> |
| |
| <listitem><para>When this signal is |
| received the systemd system manager |
| will start the |
| <filename>kbrequest.target</filename> |
| unit. This is mostly equivalent to |
| <command>systemctl start |
| kbrequest.target</command>.</para> |
| |
| <para>This signal is ignored by |
| systemd user |
| managers.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term>SIGPWR</term> |
| |
| <listitem><para>When this signal is |
| received the systemd manager |
| will start the |
| <filename>sigpwr.target</filename> |
| unit. This is mostly equivalent to |
| <command>systemctl start |
| sigpwr.target</command>.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term>SIGUSR1</term> |
| |
| <listitem><para>When this signal is |
| received the systemd manager will try |
| to reconnect to the D-Bus |
| bus.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term>SIGUSR2</term> |
| |
| <listitem><para>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 <command>systemctl |
| dump</command>.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term>SIGHUP</term> |
| |
| <listitem><para>Reloads the complete |
| daemon configuration. This is mostly |
| equivalent to <command>systemctl |
| daemon-reload</command>.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term>SIGRTMIN+0</term> |
| |
| <listitem><para>Enters default mode, starts the |
| <filename>default.target</filename> |
| unit. This is mostly equivalent to |
| <command>systemctl start |
| default.target</command>.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term>SIGRTMIN+1</term> |
| |
| <listitem><para>Enters rescue mode, |
| starts the |
| <filename>rescue.target</filename> |
| unit. This is mostly equivalent to |
| <command>systemctl isolate |
| rescue.target</command>.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term>SIGRTMIN+2</term> |
| |
| <listitem><para>Enters emergency mode, |
| starts the |
| <filename>emergency.service</filename> |
| unit. This is mostly equivalent to |
| <command>systemctl isolate |
| emergency.service</command>.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term>SIGRTMIN+3</term> |
| |
| <listitem><para>Halts the machine, |
| starts the |
| <filename>halt.target</filename> |
| unit. This is mostly equivalent to |
| <command>systemctl start |
| halt.target</command>.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term>SIGRTMIN+4</term> |
| |
| <listitem><para>Powers off the machine, |
| starts the |
| <filename>poweroff.target</filename> |
| unit. This is mostly equivalent to |
| <command>systemctl start |
| poweroff.target</command>.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term>SIGRTMIN+5</term> |
| |
| <listitem><para>Reboots the machine, |
| starts the |
| <filename>reboot.target</filename> |
| unit. This is mostly equivalent to |
| <command>systemctl start |
| reboot.target</command>.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term>SIGRTMIN+6</term> |
| |
| <listitem><para>Reboots the machine via kexec, |
| starts the |
| <filename>kexec.target</filename> |
| unit. This is mostly equivalent to |
| <command>systemctl start |
| kexec.target</command>.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term>SIGRTMIN+13</term> |
| |
| <listitem><para>Immediately halts the machine.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term>SIGRTMIN+14</term> |
| |
| <listitem><para>Immediately powers off the machine.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term>SIGRTMIN+15</term> |
| |
| <listitem><para>Immediately reboots the machine.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term>SIGRTMIN+16</term> |
| |
| <listitem><para>Immediately reboots the machine with kexec.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term>SIGRTMIN+20</term> |
| |
| <listitem><para>Enables display of |
| status messages on the console, as |
| controlled via |
| <varname>systemd.show_status=1</varname> |
| on the kernel command |
| line.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term>SIGRTMIN+21</term> |
| |
| <listitem><para>Disables display of |
| status messages on the console, as |
| controlled via |
| <varname>systemd.show_status=0</varname> |
| on the kernel command |
| line.</para></listitem> |
| </varlistentry> |
| </variablelist> |
| </refsect1> |
| |
| <refsect1> |
| <title>Environment</title> |
| |
| <variablelist> |
| <varlistentry> |
| <term><varname>$SYSTEMD_LOG_LEVEL</varname></term> |
| <listitem><para>systemd reads the |
| log level from this environment |
| variable. This can be overridden with |
| <option>--log-level=</option>.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><varname>$SYSTEMD_LOG_TARGET</varname></term> |
| <listitem><para>systemd reads the |
| log target from this environment |
| variable. This can be overridden with |
| <option>--log-target=</option>.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><varname>$SYSTEMD_LOG_COLOR</varname></term> |
| <listitem><para>Controls whether |
| systemd highlights important log |
| messages. This can be overridden with |
| <option>--log-color=</option>.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><varname>$SYSTEMD_LOG_LOCATION</varname></term> |
| <listitem><para>Controls whether |
| systemd prints the code location along |
| with log messages. This can be |
| overridden with |
| <option>--log-location=</option>.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><varname>$XDG_CONFIG_HOME</varname></term> |
| <term><varname>$XDG_CONFIG_DIRS</varname></term> |
| <term><varname>$XDG_DATA_HOME</varname></term> |
| <term><varname>$XDG_DATA_DIRS</varname></term> |
| |
| <listitem><para>The systemd user |
| manager uses these variables in |
| accordance to the <ulink |
| url="http://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html">XDG |
| Base Directory specification</ulink> |
| to find its configuration.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><varname>$SYSTEMD_UNIT_PATH</varname></term> |
| |
| <listitem><para>Controls where systemd |
| looks for unit |
| files.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><varname>$SYSTEMD_SYSVINIT_PATH</varname></term> |
| |
| <listitem><para>Controls where systemd |
| looks for SysV init scripts.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><varname>$SYSTEMD_SYSVRCND_PATH</varname></term> |
| |
| <listitem><para>Controls where systemd |
| looks for SysV init script runlevel link |
| farms.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><varname>$LISTEN_PID</varname></term> |
| <term><varname>$LISTEN_FDS</varname></term> |
| |
| <listitem><para>Set by systemd for |
| supervised processes during |
| socket-based activation. See |
| <citerefentry><refentrytitle>sd_listen_fds</refentrytitle><manvolnum>3</manvolnum></citerefentry> |
| for more information. |
| </para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><varname>$NOTIFY_SOCKET</varname></term> |
| |
| <listitem><para>Set by systemd for |
| supervised processes for status and |
| start-up completion notification. See |
| <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry> |
| for more information. |
| </para></listitem> |
| </varlistentry> |
| </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.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 shell is |
| spawned. 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.confirm_spawn=</varname></term> |
| |
| <listitem><para>Takes a boolean |
| argument. If <option>true</option> |
| asks for confirmation when spawning |
| processes. Defaults to |
| <option>false</option>.</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> |
| |
| <varlistentry> |
| <term><varname>systemd.sysv_console=</varname></term> |
| |
| <listitem><para>Takes a boolean |
| argument. If <option>true</option> |
| output of SysV init scripts will be |
| directed to the console. Defaults to |
| <option>true</option>, unless |
| <option>quiet</option> is passed as |
| kernel command line option in which |
| case it defaults to |
| <option>false</option>.</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.default_standard_output=</varname></term> |
| <term><varname>systemd.default_standard_error=</varname></term> |
| <listitem><para>Controls default |
| standard output/error output for |
| services, with the same effect as the |
| <option>--default-standard-output=</option> |
| resp. <option>--default-standard-error=</option> |
| command line arguments described |
| above.</para></listitem> |
| </varlistentry> |
| |
| </variablelist> |
| </refsect1> |
| |
| <refsect1> |
| <title>Sockets and FIFOs</title> |
| |
| <variablelist> |
| <varlistentry> |
| <term><filename>@/org/freedesktop/systemd1/notify</filename></term> |
| |
| <listitem><para>Daemon status |
| notification socket. This is an AF_UNIX |
| datagram socket in the Linux abstract |
| namespace, and is used to implement |
| the daemon notification logic as |
| implemented by |
| <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para></listitem> |
| |
| </varlistentry> |
| |
| <varlistentry> |
| <term><filename>@/org/freedesktop/systemd1/logger</filename></term> |
| |
| <listitem><para>Used internally by the |
| <filename>systemd-logger.service</filename> |
| unit to connect STDOUT and/or STDERR |
| of spawned processes to |
| <citerefentry><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry> |
| or the kernel log buffer. This is an |
| AF_UNIX stream socket in the Linux |
| abstract namespace.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><filename>@/org/freedesktop/systemd1/shutdown</filename></term> |
| |
| <listitem><para>Used internally by the |
| <citerefentry><refentrytitle>shutdown</refentrytitle><manvolnum>8</manvolnum></citerefentry> |
| tool to implement delayed |
| shutdowns. This is an AF_UNIX datagram |
| socket in the Linux abstract |
| namespace.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><filename>@/org/freedesktop/systemd1/private</filename></term> |
| |
| <listitem><para>Used internally as |
| communication channel between |
| <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry> |
| and the systemd process. This is an |
| AF_UNIX stream socket in the Linux |
| abstract namespace. This interface is |
| private to systemd and should not be |
| used in external |
| projects.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><filename>/dev/initctl</filename></term> |
| |
| <listitem><para>Limited compatibility |
| support for the SysV client interface, |
| as implemented by the |
| <filename>systemd-initctl.service</filename> |
| unit. This is a named pipe in the file |
| system. This interface is obsolete and |
| should not be used in new |
| applications.</para></listitem> |
| </varlistentry> |
| </variablelist> |
| </refsect1> |
| |
| <refsect1> |
| <title>See Also</title> |
| <para> |
| <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>, |
| <citerefentry><refentrytitle>systemadm</refentrytitle><manvolnum>1</manvolnum></citerefentry>, |
| <citerefentry><refentrytitle>systemd-notify</refentrytitle><manvolnum>1</manvolnum></citerefentry>, |
| <citerefentry><refentrytitle>daemon</refentrytitle><manvolnum>7</manvolnum></citerefentry>, |
| <citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>7</manvolnum></citerefentry>, |
| <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>, |
| <citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>5</manvolnum></citerefentry>, |
| <citerefentry><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry> |
| </para> |
| </refsect1> |
| |
| </refentry> |