man: update description of polkit rules for systemd1

[thirdparty/systemd.git] / man / org.freedesktop.systemd1.xml

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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
  "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd" >
<!-- SPDX-License-Identifier: LGPL-2.1+ -->

<refentry id="org.freedesktop.systemd1" xmlns:xi="http://www.w3.org/2001/XInclude">
  <refentryinfo>
    <title>org.freedesktop.systemd1</title>
    <productname>systemd</productname>
  </refentryinfo>

  <refmeta>
    <refentrytitle>org.freedesktop.systemd1</refentrytitle>
    <manvolnum>5</manvolnum>
  </refmeta>

  <refnamediv>
    <refname>org.freedesktop.systemd1</refname>
    <refpurpose>The D-Bus interface of systemd-systemdd</refpurpose>
  </refnamediv>

  <refsect1>
    <title>Introduction</title>

    <para>
    <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry> and its
    auxiliary daemons expose a number of APIs over D-Bus. This page describes the various APIs exposed by the
    system and service manager itself, and does not cover the auxiliary daemons.
    </para>

    <para>The service manager exposes a number of objects on the bus: one
    <interfacename>Manager</interfacename> object as central entry point for clients, and individual objects
    for each unit and for each queued job. The unit objects each implement a generic
    <interfacename>Unit</interfacename> interface plus a type-specific interface. For example, service units
    implement <interfacename>org.freedesktop.systemd1.Unit</interfacename> as well as
    <interfacename>org.freedesktop.system1.Service</interfacename>. The manager object can be used to list
    unit and job objects, or to directly convert a unit name or job id into a bus path of the corresponding
    D-Bus object.</para>

    <para>Properties exposing time values are usually encoded in microseconds (usec) on the bus, even if
    their corresponding settings in the unit files are in seconds.</para>

    <para>In contrast to most of the other services of the systemd suite PID 1 does not use PolicyKit for
    controlling access to privileged operations, but relies exclusively on the low-level D-Bus policy
    language. (This is done in order to avoid a cyclic dependency between PolicyKit and systemd/PID 1.) This
    means that sensitive operations exposed by PID 1 on the bus are generally not available to unprivileged
    processes directly. However some (such as shutdown/reboot/suspend) are made available through the D-Bus
    API of logind, see
    <citerefentry><refentrytitle>org.freedesktop.login1</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
    </para>
  </refsect1>

  <refsect1>
    <title>The Manager Object</title>

    <para>The main entry point object is available on the fixed
    <constant>/org/freedesktop/systemd1</constant> object path:</para>

    <programlisting>
$ gdbus introspect --system \
        --dest org.freedesktop.systemd1 \
        --object-path /org/freedesktop/systemd1

node /org/freedesktop/systemd1 {
  interface org.freedesktop.systemd1.Manager {
    methods:
      GetUnit(in  s name,
              out o unit);
      GetUnitByPID(in  u pid,
                   out o unit);
      LoadUnit(in  s name,
               out o unit);
      StartUnit(in  s name,
                in  s mode,
                out o job);
      StartUnitReplace(in  s old_unit,
                       in  s new_unit,
                       in  s mode,
                       out o job);
      StopUnit(in  s name,
               in  s mode,
               out o job);
      ReloadUnit(in  s name,
                 in  s mode,
                 out o job);
      RestartUnit(in  s name,
                  in  s mode,
                  out o job);
      TryRestartUnit(in  s name,
                     in  s mode,
                     out o job);
      ReloadOrRestartUnit(in  s name,
                          in  s mode,
                          out o job);
      ReloadOrTryRestartUnit(in  s name,
                             in  s mode,
                             out o job);
      KillUnit(in  s name,
               in  s who,
               in  i signal);
      ResetFailedUnit(in  s name);
      GetJob(in  u id,
             out o job);
      CancelJob(in  u id);
      ClearJobs();
      ResetFailed();
      ListUnits(out a(ssssssouso) units);
      ListJobs(out a(usssoo) jobs);
      Subscribe();
      Unsubscribe();
      Reload();
      Reexecute();
      Exit();
      Reboot();
      PowerOff();
      Halt();
      KExec();
      SwitchRoot(in  s new_root,
                 in  s init);
      SetEnvironment(in  as names);
      UnsetEnvironment(in  as names);
      UnsetAndSetEnvironment(in  as unset,
                             in  as set);
      ListUnitFiles(out a(ss) files);
      GetUnitFileState(in  s file,
                       out s state);
      EnableUnitFiles(in  as files,
                      in  b runtime,
                      in  b force,
                      out b carries_install_info,
                      out a(sss) changes);
      DisableUnitFiles(in  as files,
                       in  b runtime,
                       out a(sss) changes);
      ReenableUnitFiles(in  as files,
                        in  b runtime,
                        in  b force,
                        out b carries_install_info,
                        out a(sss) changes);
      LinkUnitFiles(in  as files,
                    in  b runtime,
                    in  b force,
                    out a(sss) changes);
      PresetUnitFiles(in  as files,
                      in  b runtime,
                      in  b force,
                      out b carries_install_info,
                      out a(sss) changes);
      MaskUnitFiles(in  as files,
                    in  b runtime,
                    in  b force,
                    out a(sss) changes);
      UnmaskUnitFiles(in  as files,
                      in  b runtime,
                      out a(sss) changes);
      SetDefaultTarget(in  as files,
                       out a(sss) changes);
      GetDefaultTarget(out s name);
      SetUnitProperties(in  s name,
                        in  b runtime,
                        in  a(sv) properties);
      StartTransientUnit(in  s name,
                         in  s mode,
                         in  a(sv) properties,
                         in  a(sa(sv)) aux,
                         out o job);
    signals:
      UnitNew(s id,
              o unit);
      UnitRemoved(s id,
                  o unit);
      JobNew(u id,
             o job,
             s unit);
      JobRemoved(u id,
                 o job,
                 s unit,
                 s result);
      StartupFinished(t firmware,
                      t loader,
                      t kernel,
                      t initrd,
                      t userspace,
                      t total);
      UnitFilesChanged();
      Reloading(b active);
    properties:
      readonly s Version = 'systemd 205';
      readonly s Features = '+PAM +LIBWRAP +AUDIT +SELINUX +IMA +SYSVINIT +LIBCRYPTSETUP +GCRYPT +ACL +XZ';
      readonly s Tainted = '';
      readonly t FirmwareTimestamp = 0;
      readonly t FirmwareTimestampMonotonic = 0;
      readonly t LoaderTimestamp = 0;
      readonly t LoaderTimestampMonotonic = 0;
      readonly t KernelTimestamp = 0;
      readonly t KernelTimestampMonotonic = 0;
      readonly t InitRDTimestamp = 0;
      readonly t InitRDTimestampMonotonic = 0;
      readonly t UserspaceTimestamp = 1373892700771932;
      readonly t UserspaceTimestampMonotonic = 347348267507;
      readonly t FinishTimestamp = 1373892717621078;
      readonly t FinishTimestampMonotonic = 347365116654;
      readonly t GeneratorsStartTimestamp = 1374345509428734;
      readonly t GeneratorsStartTimestampMonotonic = 500549330609;
      readonly t GeneratorsFinishTimestamp = 1374345509562375;
      readonly t GeneratorsFinishTimestampMonotonic = 500549464250;
      readonly t UnitsLoadStartTimestamp = 1374345509562782;
      readonly t UnitsLoadStartTimestampMonotonic = 500549464657;
      readonly t UnitsLoadFinishTimestamp = 1374345509652212;
      readonly t UnitsLoadFinishTimestampMonotonic = 500549554088;
      readonly t SecurityStartTimestamp = 1374345509562782;
      readonly t SecurityStartTimestampMonotonic = 500549464657;
      readonly t SecurityFinishTimestamp = 1374345509652212;
      readonly t SecurityFinishTimestampMonotonic = 500549554088;
      readwrite s LogLevel = 'info';
      readwrite s LogTarget = 'journal';
      readonly u NNames = 100;
      readonly u NJobs = 0;
      readonly u NInstalledJobs = 266;
      readonly u NFailedJobs = 4;
      readonly d Progress = 1.0;
      readonly as Environment = ['PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin', 'LANG=C'];
      readonly b ConfirmSpawn = false;
      readonly b ShowStatus = true;
      readonly as UnitPath = ['/etc/systemd/system', '/run/systemd/system', '/run/systemd/generator', '/usr/local/lib/systemd/system', '/usr/lib/systemd/system'];
      readonly s DefaultStandardOutput = 'journal';
      readonly s DefaultStandardError = 'inherit';
      readwrite t RuntimeWatchdogUSec = 0;
      readwrite t ShutdownWatchdogUSec = 600000000;
      readonly s Virtualization = '';
      readonly s Architecture = 'x86-64';
  };
  interface org.freedesktop.DBus.Properties {
    ...
  };
  interface org.freedesktop.DBus.Peer {
    ...
  };
  interface org.freedesktop.DBus.Introspectable {
    ...
  };
};
    </programlisting>

    <refsect2>
      <title>Methods</title>

      <para>Note that many of the calls exist twice: once on the <interfacename>Manager</interfacename>
      object, and once on the respective unit objects. This is to optimize access times so that methods that
      belong to unit objects do not have to be called with a resolved unit path, but can be called with only
      the unit id, too.</para>

      <para><function>GetUnit()</function> may be used to get the unit object path for a unit name. It takes
      the unit name and returns the object path. If a unit has not been loaded yet by this name this call
      will fail.</para>

      <para><function>GetUnitByPID()</function> may be used to get the unit object path of the unit a process
      ID belongs to. Takes a UNIX PID and returns the object path. The PID must refer to an existing process
      of the system.</para>

      <para><function>LoadUnit()</function> is similar to <function>GetUnit()</function> but will load the
      unit from disk if possible.</para>

      <para><function>StartUnit()</function> enqeues a start job, and possibly depending jobs. Takes the unit
      to activate, plus a mode string. The mode needs to be one of <literal>replace</literal>,
      <literal>fail</literal>, <literal>isolate</literal>, <literal>ignore-dependencies</literal>,
      <literal>ignore-requirements</literal>. If <literal>replace</literal> the call will start the unit and
      its dependencies, possibly replacing already queued jobs that conflict with this. If
      <literal>fail</literal> the call will start the unit and its dependencies, but will fail if this would
      change an already queued job. If <literal>isolate</literal> the call will start the unit in question
      and terminate all units that aren't dependencies of it. If <literal>ignore-dependencies</literal> it
      will start a unit but ignore all its dependencies. If <literal>ignore-requirements</literal> it will
      start a unit but only ignore the requirement dependencies. It is not recommended to make use of the
      latter two options. Returns the newly created job object.</para>

      <para><function>StartUnitReplace()</function> is similar to <function>StartUnit()</function> but
      replaces a job that is queued for one unit by a job for another.</para>

      <para><function>StopUnit()</function> is similar to <function>StartUnit()</function> but stops the
      specified unit rather than starting it. Note that <literal>isolate</literal> mode is invalid for this
      call.</para>

      <para><function>ReloadUnit()</function>, <function>RestartUnit()</function>,
      <function>TryRestartUnit()</function>, <function>ReloadOrRestartUnit()</function>,
      <function>ReloadOrTryRestartUnit()</function> may be used to restart and/or reload a unit, and takes
      similar arguments as <function>StartUnit()</function>. Reloading is done only if the unit is already
      running and fails otherwise. If a service is restarted that isn't running it will be started, unless
      the "Try" flavor is used in which case a service that isn't running is not affected by the restart. The
      "ReloadOrRestart" flavors attempt a reload if the unit supports it and use a restart otherwise.</para>

      <para><function>KillUnit()</function> may be used to kill (i.e. send a signal to) all processes of a
      unit. Takes the unit <varname>name</varname>, an enum <varname>who</varname> and a UNIX
      <varname>signal</varname> number to send. The <varname>who</varname> enum is one of
      <literal>main</literal>, <literal>control</literal> or <literal>all</literal>. If
      <literal>main</literal>, only the main process of a unit is killed. If <literal>control</literal> only
      the control process of the unit is killed, if <literal>all</literal> all processes are killed. A
      <literal>control</literal> process is for example a process that is configured via
      <varname>ExecStop=</varname> and is spawned in parallel to the main daemon process, in order to shut it
      down.</para>

      <para><function>GetJob()</function> returns the job object path for a specific job, identified by its
      id.</para>

      <para><function>CancelJob()</function> cancels a specific job identified by its numer ID. This
      operation is also available in the <function>Cancel()</function> method of Job objects (see below), and
      exists primarily to reduce the necessary round trips to execute this operation. Note that this will not
      have any effect on jobs whose execution has already begun.</para>

      <para><function>ClearJobs()</function> flushes the job queue, removing all jobs that are still
      queued. Note that this does not have any effect on jobs whose execution has already begun, it only
      flushes jobs that are queued and have not yet begun execution.</para>

      <para><function>ResetFailedUnit()</function> resets the "failed" state of a specific unit.</para>

      <para><function>ResetFailed()</function> resets the "failed" state of all units.</para>

      <para><function>ListUnits()</function> returns an array with all currently loaded units. Note that
      units may be known by multiple names at the same name, and hence there might be more unit names loaded
      than actual units behind them. The array consists of structures with the following elements:
      <itemizedlist>
        <listitem><para>The primary unit name as string</para></listitem>

        <listitem><para>The human readable description string</para></listitem>

        <listitem><para>The load state (i.e. whether the unit file has been loaded
        successfully)</para></listitem>

        <listitem><para>The active state (i.e. whether the unit is currently started or
        not)</para></listitem>

        <listitem><para>The sub state (a more fine-grained version of the active state that is specific to
        the unit type, which the active state is not)</para></listitem>

        <listitem><para>A unit that is being followed in its state by this unit, if there is any, otherwise
        the empty string.</para></listitem>

        <listitem><para>The unit object path</para></listitem>

        <listitem><para>If there is a job queued for the job unit the numeric job id, 0
        otherwise</para></listitem>

        <listitem><para>The job type as string</para></listitem>

        <listitem><para>The job object path</para></listitem>
      </itemizedlist></para>

      <para><function>ListJobs()</function> returns an array with all currently queued jobs. Returns an array
      consisting of structures with the following elements:
      <itemizedlist>
        <listitem><para>The numeric job id</para></listitem>

        <listitem><para>The primary unit name for this job</para></listitem>

        <listitem><para>The job type as string</para></listitem>

        <listitem><para>The job state as string</para></listitem>

        <listitem><para>The job object path</para></listitem>

        <listitem><para>The unit object path</para></listitem>
      </itemizedlist></para>

      <para><function>Subscribe()</function> enables most bus signals to be sent out. Clients which are
      interested in signals need to call this function. Signals are only sent out if at least one client
      invoked this function. <function>Unsubscribe()</function> undoes the signal subscription that
      <function>Subscribe()</function> implements. It is not necessary to invoke
      <function>Unsubscribe()</function> as clients are tracked. Signals are no longer sent out as soon as
      all clients which previously asked for <function>Subscribe()</function> either closed the bus
      connection or invoked <function>Unsubscribe()</function>.</para>

      <para><function>Reload()</function> may be invoked to reload all unit files.</para>

      <para><function>Reexecute()</function> may be invoked to reexecute the main manager process. It will
      serialize its state, reexecute, and deserizalize the state again. This is useful for upgrades and is a
      more comprehensive version of <function>Reload()</function>.</para>

      <para><function>Exit()</function> may be invoked to ask the manager to exit. This is not available for
      the system manager and is useful only for user session managers.</para>

      <para><function>Reboot()</function>, <function>PowerOff()</function>, <function>Halt()</function>,
      <function>KExec()</function> may be used to ask for immediate reboot, powering down, halt or kexec
      based reboot of the system. Note that this does not shut down any services and immediately transitions
      into the reboot process. These functions are normally only called as last step of shutdown, and should
      not be called directly. To shut down the machine it is a much better choice generally to invoke
      <function>Reboot()</function> and <function>PoweOff()</function> on the
      <filename>systemd-logind</filename> manager object; see
      <citerefentry><refentrytitle>org.freedesktop.login1</refentrytitle><manvolnum>5</manvolnum></citerefentry>
      for more information.</para>

      <para><function>SwitchRoot()</function> may be used to transition to a new root directory. This is
      intended to be used by initial RAM disks. The call takes two arguments: the new root directory (which
      needs to be specified), plus an init binary path (which may be left empty, in which case it is
      automatically searched for). The state of the system manager will be serialized before the
      transition. After the transition the manager binary on the main system is invoked and replaces the old
      PID 1. All state will then be deserialized.</para>

      <para><function>SetEnvironment()</function> may be used to alter the environment block that is passed
      to all spawned processes. Takes a string array with environment variable assignments. Settings passed
      will override previously set variables.</para>

      <para><function>UnsetEnvironment()</function> may be used to unset environment variables. Takes a
      string array with environment variable names. All variables specified will be unset (if they have been
      set previously) and no longer be passed to all spawned processes. This call has no effect for variables
      that were previously not set, but will not fail in that case.</para>

      <para><function>UnsetAndSetEnvironment()</function> is a combination of
      <function>UnsetEnvironment()</function> and <function>SetEnvironment()</function>. It takes two
      lists. The first one is a list of variables to unset, the second one of assignments to set. If a
      variable is listed in both, the variable is set after this call, i.e. the set list overrides the unset
      list.</para>

      <para><function>ListUnitFiles()</function> returns an array of unit names plus their enablement
      status. Note that <function>ListUnit()</function> returns a list of units currently loaded into memory,
      while <function>ListUnitFiles()</function> returns a list of unit <emphasis>files</emphasis> that could
      be found on disk. Note that while most units are read directly from a unit file with the same name some
      units are not backed by files, and some files (templates) cannot directly be loaded as units but need
      to be instantiated.</para>

      <para><function>GetUnitFileState()</function> returns the current enablement status of specific unit
      file.</para>

      <para><function>EnableUnitFiles()</function> may be used to enable one or more units in the system (by
      creating symlinks to them in <filename>/etc</filename> or <filename>/run</filename>). It takes a list
      of unit files to enable (either just file names or full absolute paths if the unit files are residing
      outside the usual unit search paths), and two booleans: the first controls whether the unit shall be
      enabled for runtime only (true, <filename>/run</filename>), or persistently (false,
      <filename>/etc</filename>). The second one controls whether symlinks pointing to other units shall be
      replaced if necessary. This call returns one boolean and an array with the changes made. The boolean
      signals whether the unit files contained any enablement information (i.e. an [Install]) section. The
      changes list consists of structures with three strings: the type of the change (one of
      <literal>symlink</literal> or <literal>unlink</literal>), the file name of the symlink and the
      destination of the symlink. Note that most of the following calls return a changes list in the same
      format.</para>

      <para>Similarly, <function>DisableUnitFiles()</function> disables one or more units in the system,
      i.e. removes all symlinks to them in <filename>/etc</filename> and <filename>/run</filename>.</para>

      <para>Similarly, <function>ReenableUnitFiles()</function> applies the changes to one or more units that
      would result from disabling and enabling the unit quickly one after the other in an atomic
      fashion. This is useful to apply updated [Install] information contained in unit files.</para>

      <para>Similarly, <function>LinkUnitFiles()</function> links unit files (that are located outside of the
      usual unit search paths) into the unit search path.</para>

      <para>Similarly, <function>PresetUnitFiles()</function> enables/disables one or more units file
      according to the preset policy. See
      <citerefentry><refentrytitle>systemd.preset</refentrytitle><manvolnum>7</manvolnum></citerefentry> for more
      information.</para>

      <para>Similarly, <function>MaskUnitFiles()</function> masks unit files, and
      <function>UnmaskUnitFiles()</function> unmasks them again.</para>

      <para><function>SetDefaultTarget()</function> changes the <filename>default.target</filename> link. See
      <citerefentry><refentrytitle>bootup</refentrytitle><manvolnum>7</manvolnum></citerefentry> for more
      information</para>

      <para><function>GetDefaultTarget()</function> retrieves the name of the unit to which
      <filename>default.target</filename> is aliased</para>

      <para><function>SetUnitProperties()</function> may be used to modify certain unit properties at
      runtime. Not all properties may be changed at runtime, but many resource management settings (primarily
      those listed in
      <citerefentry><refentrytitle>systemd.cgroup</refentrytitle><manvolnum>5</manvolnum></citerefentry>)
      may. The changes are applied instantly, and stored on disk for future boots, unless
      <varname>runtime</varname> is true, in which case the settings only apply until the next
      reboot. <varname>name</varname> is the name of the unit to modify. <varname>properties</varname> are
      the settings to set, encoded as an array of property name and value pairs. Note that this is not a
      dictionary! Note that when setting array properties with this call this usually results in appending to
      the pre-configured array. To reset the configured arrays set the property to an empty array first, then
      append to it.</para>

      <para><function>StartTransientUnit()</function> may be used to create and start a transient unit, which
      will be released as soon as it is not running or referenced anymore or the system is
      rebooted. <varname>name</varname> is the unit name including suffix, and must be
      unique. <varname>mode</varname> is the same as in <function>StartUnit()</function>,
      <varname>properties</varname> contains properties of the unit, specified like in
      <function>SetUnitProperties()</function>. <varname>aux</varname> is currently unused and should be
      passed as empty array. See the <ulink
      url="http://www.freedesktop.org/wiki/Software/systemd/ControlGroupInterface/">New Control Group
      Interface</ulink> for more information how to make use of this functionality for resource control
      purposes.</para>
    </refsect2>

    <refsect2>
      <title>Signals</title>

      <para>Note that most signals are sent out only after <function>Subscribe()</function> has been invoked
      by at least one client. Make sure to invoke this call when subscribing to these signals!</para>

      <para><function>UnitNew()</function> and <function>UnitRemoved()</function> are sent out each time a
      new unit is loaded or unloaded. Note that this has little to do with whether a unit is available on
      disk or not, and simply reflects the units that are currently loaded into memory. The signals take two
      parameters: the primary unit name and the object path.</para>

      <para><function>JobNew()</function> and <function>JobRemoved()</function> are sent out each time a new
      job is queued or dequeued. Both signals take the numeric job ID, the bus path and the primary unit name
      for this job as argument. <function>JobRemoved()</function> also includes a result string, being one of
      <literal>done</literal>, <literal>canceled</literal>, <literal>timeout</literal>,
      <literal>failed</literal>, <literal>dependency</literal>,
      <literal>skipped</literal>. <literal>done</literal> indicates successful execution of a
      job. <literal>canceled</literal> indicates that a job has been canceled (via
      <function>CancelJob()</function> above) before it finished execution (this doesn't necessarily mean
      though that the job operation is actually cancelled too, see above). <literal>timeout</literal>
      indicates that the job timeout was reached. <literal>failed</literal> indicates that the job
      failed. <literal>dependency</literal> indicates that a job this job has been depending on failed and
      the job hence has been removed too. <literal>skipped</literal> indicates that a job was skipped because
      it didn't apply to the units current state.</para>

      <para><function>StartupFinished()</function> is sent out when startup finished. It carries six
      microsecond timespan values each indicating how much boot time has been spent in the firmware (if
      known), in the boot loader (if known), in the kernel initialization phase, in the initrd (if known), in
      userspace and in total. These values may also be calculated from the
      <varname>FirmwareTimestampMonotonic</varname>, <varname>LoaderTimestampMonotonic</varname>,
      <varname>InitRDTimestampMonotonic</varname>, <varname>UserspaceTimestampMonotonic</varname>,
      <varname>FinishTimestampMonotonic</varname> properties (see below).</para>

      <para><function>UnitFilesChanged()</function> is sent out each time the list of enabled or masked unit
      files on disk have changed.</para>

      <para><function>Reloading()</function> is sent out immediately before a daemon reload is done (with the
      boolean parameter set to True) and after a daemon reload is completed (with the boolean parameter set
      to False). This may be used by UIs to optimize UI updates</para>
    </refsect2>

    <refsect2>
      <title>Properties</title>

      <para>Most properties simply reflect the respective options in
      <filename>/etc/systemd/system.conf</filename> and the kernel command line.</para>

      <para>The others:</para>

      <para><varname>Version</varname> encodes the version string of the running systemd instance. Note that
      the version string is purely informational, it should not be parsed, one may not assume the version to
      be formatted in any particular way. We take the liberty to change the versioning scheme at any time and
      it is not part of the API.</para>

      <para><varname>Features</varname> encodes the features that have been enabled and disabled for this
      build. Enabled options are prefixed with +, disabled options with -.</para>

      <para><varname>Tainted</varname> encodes a couple of taint flags, as a colon-separated list. When
      systemd detects it is run on a system with certain problems it will set an appropriate taint
      flag. Taints may be used to lower the chance of bogus bug reports. The following taints are currently
      known: <literal>split-usr</literal>, <literal>mtab-not-symlink</literal>,
      <literal>cgroups-missing</literal>, <literal>local-hwclock</literal>. <literal>split-usr</literal> is
      set if <filename>/usr</filename> is not pre-mounted when systemd is first invoked. See
      <ulink url="http://freedesktop.org/wiki/Software/systemd/separate-usr-is-broken">
      Booting Without /usr is Broken</ulink>
      for details why this is bad. <literal>mtab-not-symlink</literal> indicates that
      <filename>/etc/mtab</filename> is not a symlink to <filename>/proc/self/mounts</filename> as
      required. <literal>cgroups-missing</literal> indicates that control groups have not been enabled in the
      kernel. <literal>local-hwclock</literal> indicates that the local RTC is configured to be in local time
      rather than UTC.</para>

      <para><varname>FirmwareTimestamp</varname>, <varname>FirmwareTimestampMonotonic</varname>,
      <varname>LoaderTimestamp</varname>, <varname>LoaderTimestampMonotonic</varname>,
      <varname>KernelTimestamp</varname>, <varname>KernelTimestampMonotonic</varname>,
      <varname>InitRDTimestamp</varname>, <varname>InitRDTimestampMonotonic</varname>,
      <varname>UserspaceTimestamp</varname>, <varname>UserspaceTimestampMonotonic</varname>,
      <varname>FinishTimestamp</varname>, <varname>FinishTimestampMonotonic</varname> encode
      <constant>CLOCK_REALTIME</constant> and <constant>CLOCK_MONOTONIC</constant> microsecond timestamps
      taken when the firmware first began execution, when the boot loader first began execution, when the
      kernel first began execution, when the initrd first began execution, when the main systemd instance
      began execution and finally, when all queued startup jobs finished execution. These values are useful
      for determining boot-time performance. Note that as monotonic time begins with the kernel startup the
      KernelTimestampMonotonic timestamp will always be 0, and FirmwareTimestampMonotonic and
      LoaderTimestampMonotonic are to be read as negative values. Also, not all fields are available,
      depending on the used firmware, boot loader or initrd implementation. In these cases the respective
      pairs of timestamps are both 0, indicating that no data is available.</para>

      <para>Similarly, the <varname>SecurityStartTimestamp</varname>,
      <varname>GeneratorsStartTimestamp</varname> and <varname>LoadUnitTimestamp</varname> (plus their
      monotonic and stop counterparts) expose performance data for uploading the security policies to the
      kernel (such as the SELinux, IMA, or SMACK policies), for running the generator tools and for loading
      the unit files</para>

      <para><varname>NNames</varname> encodes how many unit names are currently known. This only includes
      names of units that are currently loaded and can be more than actually loaded units since units may
      have more than one name.</para>

      <para><varname>NJobs</varname> encodes how many jobs are currently queued.</para>

      <para><varname>NInstalledJobs</varname> encodes how many jobs have ever been queued in total.</para>

      <para><varname>NFailedJobs</varname> encodes how many jobs have ever failed in total.</para>

      <para><varname>Progress</varname> encodes boot progress as floating point value between 0.0 and
      1.0. This value begins at 0.0 at early-boot and ends at 1.0 when boot is finished and is based on the
      number of executed and queued jobs. After startup this field is always 1.0 indicating a finished
      boot.</para>

      <para><varname>Environment</varname> encodes the environment block passed to all executed services. It
      may be altered with bus calls such as <function>SetEnvironment()</function> (see above).</para>

      <para><varname>UnitPath</varname> encodes the currently active unit file search path. It is an array of
      strings, each being one file system path</para>

      <para><varname>Virtualization</varname> contains a short ID string describing the virtualization
      technology the system runs in. On bare-metal hardware this is the empty string, otherwise an identifier
      such as <literal>kvm</literal>, <literal>vmware</literal> and so on. For a full list of IDs see
      <citerefentry><refentrytitle>systemd-detect-virt</refentrytitle><manvolnum>1</manvolnum></citerefentry>.
      Note that only the "innermost" virtualization technology is exported here. This detects both
      full-machine virtualizations (VMs) and shared-kernel virtualization (containers).</para>

      <para><varname>Architecture</varname> contains a short ID string describing the architecture the
      systemd instance is running on. This follows the same vocabulary as
      <varname>ConditionArchitectures=</varname>.</para>

      <para><varname>ControlGroup</varname> contains the root control group path of this system manager. Note
      that the root path is encoded as empty string here (not as <literal>/</literal>!), so that it can be
      appended to <filename>/sys/fs/cgroup/systemd</filename> easily. This value will be set to the empty
      string for the host instance, and some other string for container instances</para>
    </refsect2>

    <refsect2>
      <title>Security</title>

      <para>Read access is generally granted to all clients. Additionally, for unprivileged clients, some
      operations are allowed through the PolicyKit privilege system. Operations which modify unit state
      (<function>StartUnit()</function>, <function>StopUnit()</function>, <function>KillUnit()</function>,
      <function>RestartUnit()</function> and similar, <function>SetProperty</function>) require
      <interfacename>org.freedesktop.systemd1.manage-units</interfacename>. Operations which modify unit file
      enablement state (<function>EnableUnitFiles()</function>, <function>DisableUnitFiles()</function>,
      <function>ReenableUnitFiles()</function>, <function>LinkUnitFiles()</function>,
      <function>PresetUnitFiles</function>, <function>MaskUnitFiles</function>, and similar) require
      <interfacename>org.freedesktop.systemd1.manage-unit-files</interfacename>). Operations which modify the
      exported environment ( <function>SetEnvironment()</function>, <function>UnsetEnvironment()</function>,
      <function>UnsetAndSetEnvironment()</function>) require
      <interfacename>org.freedesktop.systemd1.set-environment</interfacename>.  <function>Reload()</function>
      and <function>Reexecute()</function> require
      <interfacename>org.freedesktop.systemd1.reload-daemon</interfacename>.
      </para>
    </refsect2>
  </refsect1>

  <refsect1>
    <title>Unit Objects</title>

    <programlisting interface="org.freedesktop.systemd1.Unit">
$ gdbus introspect --system --dest org.freedesktop.systemd1 \
      --object-path /org/freedesktop/systemd1/unit/avahi_2ddaemon_2eservice

node /org/freedesktop/systemd1/unit/avahi_2ddaemon_2eservice {
  interface org.freedesktop.systemd1.Unit {
    methods:
      Start(in  s mode,
            out o job);
      Stop(in  s mode,
           out o job);
      Reload(in  s mode,
             out o job);
      Restart(in  s mode,
              out o job);
      TryRestart(in  s mode,
                 out o job);
      ReloadOrRestart(in  s mode,
                      out o job);
      ReloadOrTryRestart(in  s mode,
                         out o job);
      Kill(in  s who,
           in  i signal);
      ResetFailed();
      SetProperties(in  b runtime,
                    in  a(sv) properties);
    signals:
    properties:
      readonly s Id = 'avahi-daemon.service';
      readonly as Names = ['avahi-daemon.service'];
      readonly s Following = '';
      readonly as Requires = ['avahi-daemon.socket', 'dbus.socket', 'basic.target'];
      readonly as RequiresOverridable = [];
      readonly as Requisite = [];
      readonly as RequisiteOverridable = [];
      readonly as Wants = [];
      readonly as BindsTo = [];
      readonly as PartOf = [];
      readonly as RequiredBy = [];
      readonly as RequiredByOverridable = [];
      readonly as WantedBy = ['multi-user.target'];
      readonly as BoundBy = [];
      readonly as ConsistsOf = [];
      readonly as Conflicts = ['shutdown.target'];
      readonly as ConflictedBy = [];
      readonly as Before = ['shutdown.target', 'multi-user.target'];
      readonly as After = ['avahi-daemon.socket', 'systemd-journald.socket', 'dbus.socket', 'basic.target'];
      readonly as OnFailure = [];
      readonly as Triggers = [];
      readonly as TriggeredBy = ['avahi-daemon.socket'];
      readonly as PropagatesReloadTo = [];
      readonly as ReloadPropagatedFrom = [];
      readonly as RequiresMountsFor = [];
      readonly s Description = 'Avahi mDNS/DNS-SD Stack';
      readonly s SourcePath = '';
      readonly as DropInPaths = [];
      readonly as Documentation = [];
      readonly s LoadState = 'loaded';
      readonly s ActiveState = 'active';
      readonly s SubState = 'running';
      readonly s FragmentPath = '/usr/lib/systemd/system/avahi-daemon.service';
      readonly s UnitFileState = 'enabled';
      readonly t InactiveExitTimestamp = 1368576738559539;
      readonly t InactiveExitTimestampMonotonic = 22561234;
      readonly t ActiveEnterTimestamp = 1368576738648314;
      readonly t ActiveEnterTimestampMonotonic = 22650009;
      readonly t ActiveExitTimestamp = 0;
      readonly t ActiveExitTimestampMonotonic = 0;
      readonly t InactiveEnterTimestamp = 0;
      readonly t InactiveEnterTimestampMonotonic = 0;
      readonly b CanStart = true;
      readonly b CanStop = true;
      readonly b CanReload = true;
      readonly b CanIsolate = false;
      readonly (uo) Job = (0, '/org/freedesktop/systemd1/unit/avahi_2ddaemon_2eservice');
      readonly b StopWhenUnneeded = false;
      readonly b RefuseManualStart = false;
      readonly b RefuseManualStop = false;
      readonly b AllowIsolate = false;
      readonly b DefaultDependencies = true;
      readonly b OnFailureIsolate = false;
      readonly b IgnoreOnIsolate = false;
      readonly b IgnoreOnSnapshot = false;
      readonly b NeedDaemonReload = false;
      readonly t JobTimeoutUSec = 0;
      readonly t ConditionTimestamp = 1368576738557978;
      readonly t ConditionTimestampMonotonic = 22559674;
      readonly b ConditionResult = true;
      readonly a(sbbsi) Conditions = [('ConditionVirtualization, false, false, 'no', 1)];
      readonly (ss) LoadError = ('', '');
      readonly b Transient = false;
  };
  interface org.freedesktop.systemd1.Service {
    ...
  };
  interface org.freedesktop.DBus.Properties {
    ...
  };
  interface org.freedesktop.DBus.Peer {
    ...
  };
  interface org.freedesktop.DBus.Introspectable {
    ...
  };
};
    </programlisting>

    <refsect2>
      <title>Methods</title>

      <para><function>Start()</function>, <function>Stop()</function>, <function>Reload()</function>,
      <function>Restart()</function>, <function>TryRestart()</function>,
      <function>ReloadOrRestart()</function>, <function>ReloadOrTryRestart()</function>,
      <function>Kill()</function>, <function>ResetFailed()</function>, and
      <function>SetProperties()</function> implement the same operation as the respective method calls on the
      <interfacename>Manager</interfacename> object (see above), however operate on the unit object and hence
      do not take a unit name parameter. Invoking the methods directly on the Manager object has the
      advantage of not requiring a <function>GetUnit()</function> call to get the unit object for a specific
      unit name. Calling the methods on the Manager object is hence a round trip optimization.</para>
    </refsect2>

    <refsect2>
      <title>Properties</title>

      <para><varname>Id</varname> contains the primary name of the unit.</para>

      <para><varname>Names</varname> contains all names of the unit, including the primary name that is also
      exposed in <varname>Id</varname>.</para>

      <para><varname>Following</varname> either contains the empty string or contains the name of another
      unit that this unit follows in state. This is used for some device units which reflect the unit state
      machine of another unit, and which other unit this is might possibly change.</para>

      <para><varname>Requires</varname>, <varname>RequiresOverridable</varname>,
      <varname>Requisite</varname>, <varname>RequisiteOverridable</varname>, <varname>Wants</varname>,
      <varname>BindsTo</varname>, <varname>RequiredBy</varname>, <varname>RequiredByOverridable</varname>,
      <varname>WantedBy</varname>, <varname>BoundBy</varname>, <varname>Conflicts</varname>,
      <varname>ConflictedBy</varname>, <varname>Before</varname>, <varname>After</varname>,
      <varname>OnFailure</varname>, <varname>Triggers</varname>, <varname>TriggeredBy</varname>,
      <varname>PropagatesReloadTo</varname>, <varname>RequiresMountsFor</varname> contain arrays which encode
      the dependencies and their inverse dependencies (where this applies), as configured in the unit file or
      determined automatically. </para>

      <para><varname>Description</varname> contains the human readable description string for the
      unit.</para>

      <para><varname>SourcePath</varname> contains the path to a configuration file this unit is
      automatically generated from in case it is not a native unit (in which case it contains the empty
      string). For example, all mount units generated from <filename>/etc/fstab</filename> have this field
      set to this value.</para>

      <para><varname>Documentation</varname> contains a string array with URLs of documentation for this
      unit.</para>

      <para><varname>LoadState</varname> contains a state value that reflects whether the configuration file
      of this unit has been loaded. The following states are currently defined: <literal>loaded</literal>,
      <literal>error</literal>, <literal>masked</literal>. <literal>loaded</literal> indicates that the
      configuration was successfully loaded. <literal>error</literal> indicates that the configuration failed
      to load, the <varname>LoadError</varname> field (see below) contains information about the cause of
      this failure. <literal>masked</literal> indicates that the unit is currently masked out (i.e. symlinked
      to <filename>/dev/null</filename> or empty). Note that the <varname>LoadState</varname> is fully
      orthogonal to the <varname>ActiveState</varname> (see below) as units without valid loaded
      configuration might be active (because configuration might have been reloaded at a time where a unit
      was already active).</para>

      <para><varname>ActiveState</varname> contains a state value that reflects whether the unit is currently
      active or not. The following states are currently defined: <literal>active</literal>,
      <literal>reloading</literal>, <literal>inactive</literal>, <literal>failed</literal>,
      <literal>activating</literal>, <literal>deactivating</literal>. <literal>active</literal> indicates
      that unit is active (obviously...). <literal>reloading</literal> indicates that the unit is active and
      currently reloading its configuration. <literal>inactive</literal> indicates that it is inactive and
      the previous run was successful or no previous run has taken place yet. <literal>failed</literal>
      indicates that it is inactive and the previous run was not successful (more information about the
      reason for this is available on the unit type specific interfaces, for example for services in the
      <varname>Result</varname> property, see below). <literal>activating</literal> indicates that the unit
      has previously been inactive but is currently in the process of entering an active state. Conversely
      <literal>deactivating</literal> indicates that the unit is currently in the process of
      deactivation.</para>

      <para><varname>SubState</varname> encodes states of the same state machine that
      <varname>ActiveState</varname> covers, but knows more fine-grained states that are
      unit-type-specific. Where <varname>ActiveState</varname> only covers six high-level states,
      <varname>SubState</varname> covers possibly many more low-level unit-type-specific states that are
      mapped to the six high-level states. Note that multiple low-level states might map to the same
      high-level state, but not vice versa. Not all high-level states have low-level counterparts on all unit
      types. At this point the low-level states are not documented here, and are more likely to be extended
      later on than the common high-level states explained above.</para>

      <para><varname>FragmentPath</varname> contains the unit file path this unit was read from, if there is
      any (if not this contains the empty string).</para>

      <para><varname>UnitFileState</varname> encodes the install state of the unit file of
      <varname>FragmentPath</varname>. It currently knows the following states: <literal>enabled</literal>,
      <literal>enabled-runtime</literal>, <literal>linked</literal>, <literal>linked-runtime</literal>,
      <literal>masked</literal>, <literal>masked-runtime</literal>, <literal>static</literal>,
      <literal>disabled</literal>, <literal>invalid</literal>. <literal>enabled</literal> indicates that a
      unit file is permanently enabled. <literal>enable-runtime</literal> indicates the unit file is only
      temporarily enabled, and will no longer be enabled after a reboot (that means, it is enabled via
      <filename>/run</filename> symlinks, rather than <filename>/etc</filename>). <literal>linked</literal>
      indicates that a unit is linked into <filename>/etc</filename> permanently, <literal>linked</literal>
      indicates that a unit is linked into <filename>/run</filename> temporarily (until the next
      reboot). <literal>masked</literal> indicates that the unit file is masked permanently,
      <literal>masked-runtime</literal> indicates that it is only temporarily masked in
      <filename>/run</filename>, until the next reboot. <literal>static</literal> indicates that the unit is
      statically enabled, i.e. always enabled and doesn't need to be enabled
      explicitly. <literal>invalid</literal> indicates that it could not be determined whether the unit file
      is enabled.</para>

      <para><varname>InactiveExitTimestamp</varname>, <varname>InactiveExitTimestampMonotonic</varname>,
      <varname>ActiveEnterTimestamp</varname>, <varname>ActiveEnterTimestampMonotonic</varname>,
      <varname>ActiveExitTimestamp</varname>, <varname>ActiveExitTimestampMonotonic</varname>,
      <varname>InactiveEnterTimestamp</varname>, <varname>InactiveEnterTimestampMonotonic</varname> contain
      <constant>CLOCK_REALTIME</constant> and <constant>CLOCK_MONOTONIC</constant> 64-bit microsecond
      timestamps of the last time a unit left the inactive state, entered the active state, exited the active
      state, or entered an inactive state. These are the points in time where the unit transitioned
      <literal>inactive</literal>/<literal>failed</literal> → <literal>activating</literal>,
      <literal>activating</literal> → <literal>active</literal>, <literal>active</literal> →
      <literal>deactivating</literal>, and finally <literal>deactivating</literal> →
      <literal>inactive</literal>/<literal>failed</literal>. The fields are 0 in case such a transition has
      not been recording on this boot yet.</para>

      <para><varname>CanStart</varname>, <varname>CanStop</varname>, <varname>CanReload</varname> encodes as
      booleans whether the unit supports the start, stop or reload operations. Even if a unit supports such
      an operation the client might not necessary have the right privileges to execute them.</para>

      <para><varname>CanIsolate</varname> encodes as boolean whether the unit may be started in isolation
      mode.</para>

      <para><varname>Job</varname> encodes the job ID and job object path of the job currently scheduled or
      executed for this unit, if there is any. If no job is scheduled or executed the job id field will be
      0.</para>

      <para><varname>StopWhenUnneeded</varname>, <varname>RefuseManualStart</varname>,
      <varname>RefuseManualStop</varname>, <varname>AllowIsolate</varname>,
      <varname>DefaultDependencies</varname>, <varname>OnFailureIsolate</varname>,
      <varname>IgnoreOnIsolate</varname>, <varname>IgnoreOnSnapshot</varname> map directly to the
      corresponding configuration booleans in the unit file.</para>

      <para><varname>DefaultControlGroup</varname> contains the main control group of this unit as a
      string. This refers to a group in systemd's own <literal>name=systemd</literal> hierarchy, which
      systemd uses to watch and manipulate the unit and all its processes.</para>

      <para><varname>NeedDaemonReload</varname> is a boolean that indicates whether the configuration file
      this unit is loaded from (i.e. <varname>FragmentPath</varname> or <varname>SourcePath</varname>) has
      changed since the configuration was read and hence whether a configuration reload is
      recommended.</para>

      <para><varname>JobTimeoutUSec</varname> maps directly to the corresponding configuration setting in the
      unit file.</para>

      <para><varname>ConditionTimestamp</varname> and <varname>ConditionTimestampMonotonic</varname> contain
      the <constant>CLOCK_REALTIME</constant>/<constant>CLOCK_MONOTONIC</constant> microsecond timestamps of
      the last time the configured conditions of the unit have been checked, or 0 if they have never been
      checked. Conditions are checked when a unit is requested to start.</para>

      <para><varname>ConditionResult</varname> contains the condition result of the last time the configured
      conditions of this unit were checked. </para>

      <para><varname>Conditions</varname> contains all configured conditions of the unit. For each condition
      five fields are given: condition type (e.g. <varname>ConditionPathExists</varname>), whether the
      condition is a trigger condition, whether the condition is reversed, the right hand side of the
      condition (e.g. the path in case of <varname>ConditionPathExists</varname>), and the status. The status
      can be 0, in which case the condition hasn't been checked yet, a positive value, in which case the
      condition passed, or a negative value, in which case the condition failed. Currently only 0, +1, and -1
      are used, but additional values may be used in the future, retaining the meaning of
      zero/positive/negative values</para>

      <para><varname>LoadError</varname> contains a pair of strings. If the unit failed to load (as encoded
      in <varname>LoadState</varname>, see above), then this will include a D-Bus error pair consisting of
      the error ID and an explanatory human readable string of what happened. If it succeeded to load this
      will be a pair of empty strings.</para>

      <para><varname>Transient</varname> contains a boolean that indicates whether the unit was created as
      transient unit (i.e. via <function>CreateTransientUnit()</function> on the manager object)</para>
    </refsect2>

    <refsect2>
      <title>Security</title>

      <para>Similarly to methods on the <interfacename>Manager</interfacename> object, read-only access is
      allowed for everyone. All operations are allowed for clients with the
      <constant>CAP_SYS_ADMIN</constant> capability or when the
      <interfacename>org.freedesktop.systemd1.manage-units</interfacename> privilege is granted by
      PolicyKit.</para>
    </refsect2>
  </refsect1>

  <refsect1>
    <title>Service Unit Objects</title>

    <para>All service unit objects implement the
    <interfacename>org.freedesktop.systemd1.Service</interfacename> interface (described here) in addition to
    the generic <interfacename>org.freedesktop.systemd1.Unit</interfacename> interface (see above).</para>

    <programlisting interface="org.freedesktop.systemd1.Service">
$ gdbus introspect --system --dest org.freedesktop.systemd1 \
      --object-path /org/freedesktop/systemd1/unit/avahi_2ddaemon_2eservice

  interface org.freedesktop.systemd1.Unit {
    ...
  };
  interface org.freedesktop.systemd1.Service {
    methods:
    signals:
    properties:
      readonly s Type = 'dbus';
      readonly s Restart = 'no';
      readonly s PIDFile = '';
      readonly s NotifyAccess = 'main';
      readonly t RestartUSec = 100000;
      readonly t TimeoutUSec = 90000000;
      readonly t WatchdogUSec = 0;
      readonly t WatchdogTimestamp = 0;
      readonly t WatchdogTimestampMonotonic = 0;
      readonly t StartLimitInterval = 10000000;
      readonly u StartLimitBurst = 5;
      readwrite s StartLimitAction = 'none
      readonly s Slice = 'system.slice';
      readonly s ControlGroup = '/system.slice/avahi-daemon.service';
      readonly a(sasbttuii) ExecStartPre = [];
      readonly a(sasbttuii) ExecStart = [('/usr/sbin/avahi-daemon', ['/usr/sbin/avahi-daemon', '-s'], false, 0, 0, 0, 0, 0, 0, 0)];
      readonly a(sasbttuii) ExecStartPost = [];
      readonly a(sasbttuii) ExecReload = [('/usr/sbin/avahi-daemon', ['/usr/sbin/avahi-daemon', '-r'], false, 0, 0, 0, 0, 0, 0, 0)];
      readonly a(sasbttuii) ExecStop = [];
      readonly a(sasbttuii) ExecStopPost = [];
      readonly as Environment = [];
      readonly a(sb) EnvironmentFiles = [];
      readonly u UMask = 18;
      readonly t LimitCPU = 18446744073709551615;
      readonly t LimitFSIZE = 18446744073709551615;
      readonly t LimitDATA = 18446744073709551615;
      readonly t LimitSTACK = 18446744073709551615;
      readonly t LimitCORE = 18446744073709551615;
      readonly t LimitRSS = 18446744073709551615;
      readonly t LimitNOFILE = 4096;
      readonly t LimitAS = 18446744073709551615;
      readonly t LimitNPROC = 256963;
      readonly t LimitMEMLOCK = 65536;
      readonly t LimitLOCKS = 18446744073709551615;
      readonly t LimitSIGPENDING = 256963;
      readonly t LimitMSGQUEUE = 819200;
      readonly t LimitNICE = 0;
      readonly t LimitRTPRIO = 0;
      readonly t LimitRTTIME = 18446744073709551615;
      readonly s WorkingDirectory = '';
      readonly s RootDirectory = '';
      readonly i OOMScoreAdjust = 0;
      readonly i Nice = 0;
      readonly i IOScheduling = 0;
      readonly i CPUSchedulingPolicy = 0;
      readonly i CPUSchedulingPriority = 0;
      readonly ay CPUAffinity = [];
      readonly t TimerSlackNSec = 50000;
      readonly b CPUSchedulingResetOnFork = false;
      readonly b NonBlocking = false;
      readonly s StandardInput = 'null';
      readonly s StandardOutput = 'journal';
      readonly s StandardError = 'inherit';
      readonly s TTYPath = '';
      readonly b TTYReset = false;
      readonly b TTYVHangup = false;
      readonly b TTYVTDisallocate = false;
      readonly i SyslogPriority = 30;
      readonly s SyslogIdentifier = '';
      readonly b SyslogLevelPrefix = true;
      readonly s Capabilities = '';
      readonly i SecureBits = 0;
      readonly t CapabilityBoundingSet = 18446744073709551615;
      readonly s User = '';
      readonly s Group = '';
      readonly as SupplementaryGroups = [];
      readonly s TCPWrapName = '';
      readonly s PAMName = '';
      readonly as ReadWriteDirectories = [];
      readonly as ReadOnlyDirectories = [];
      readonly as InaccessibleDirectories = [];
      readonly t MountFlags = 0;
      readonly b PrivateTmp = false;
      readonly b PrivateNetwork = false;
      readonly b SameProcessGroup = false;
      readonly s UtmpIdentifier = '';
      readonly b IgnoreSIGPIPE = true;
      readonly b NoNewPrivileges = false;
      readonly au SystemCallFilter = [];
      readonly s KillMode = 'control-group';
      readonly i KillSignal = 15;
      readonly b SendSIGKILL = true;
      readonly b SendSIGHUP = false;
      readonly b CPUAccounting = false;
      readonly t CPUShares = 1024;
      readonly b BlockIOAccounting = false;
      readonly t BlockIOWeight = 1000;
      readonly a(st) BlockIODeviceWeight = [];
      readonly a(st) BlockIOReadBandwidth=;
      readonly a(st) BlockIOWriteBandwidth=;
      readonly b MemoryAccounting = false;
      readonly t MemoryLimit = 18446744073709551615;
      readonly s DevicePolicy = 'auto';
      readonly a(ss) DeviceAllow = [];
      readonly b PermissionsStartOnly = false;
      readonly b RootDirectoryStartOnly = false;
      readonly b RemainAfterExit = false;
      readonly t ExecMainStartTimestamp = 1368576738559537;
      readonly t ExecMainStartTimestampMonotonic = 22561233;
      readonly t ExecMainExitTimestamp = 1368576738559537;
      readonly t ExecMainExitTimestampMonotonic = 22561233;
      readonly u ExecMainPID = 666;
      readonly i ExecMainCode = 0;
      readonly i ExecMainStatus = 0;
      readonly u MainPID = 666;
      readonly u ControlPID = 0;
      readonly s BusName = 'org.freedesktop.Avahi';
      readonly s StatusText = 'Server startup complete. Host name is fedora.local. Local service cookie is 2431121142.';
      readonly s Result = 'success';
  };
  interface org.freedesktop.DBus.Properties {
    ...
  };
  interface org.freedesktop.DBus.Peer {
    ...
  };
  interface org.freedesktop.DBus.Introspectable {
    ...
  };
};
    </programlisting>

    <refsect2>
      <title>Properties</title>

      <para>Most properties of the Service interface map directly to the corresponding settings in service
      unit files. For the sake of brevity, here's a list of all exceptions only:</para>

      <para><varname>WatchdogTimestamp</varname> and <varname>WatchdogTimestampMonotonic</varname> contain
      <constant>CLOCK_REALTIME</constant>/<constant>CLOCK_MONOTONIC</constant> microsecond timestamps of the
      last watchdog ping received from the service, or 0 if none was ever received.</para>

      <para><varname>ExecStartPre</varname>, <varname>ExecStart</varname>, <varname>ExecStartPost</varname>,
      <varname>ExecReload</varname>, <varname>ExecStop</varname>, <varname>ExecStop</varname> each are arrays
      of structures each containing: the binary path to execute; an array with all arguments to pass to the
      executed command, starting with argument 0; a boolean whether it should be considered a failure if the
      process exits uncleanly; two pairs of
      <constant>CLOCK_REALTIME</constant>/<constant>CLOCK_MONOTONIC</constant> microsecond timestamps when
      the process began and finished running the last time, or 0 if it never ran or never finished running;
      the PID of the process, or 0 if it has not run yet; the exit code and status of the last run. This
      field hence maps more or less to the corresponding setting in the service unit file but is augmented
      with runtime data.</para>

      <para><varname>LimitCPU</varname> (and related properties) map more or less directly to the
      corresponding settings in the service unit files, however are set to 18446744073709551615 (i.e. -1) if
      they aren't set.</para>

      <para><varname>Capabilities</varname> contains the configured capabilities, as formatted with
      <citerefentry project='man-pages'><refentrytitle>cap_to_text</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
      </para>

      <para><varname>SecureBits</varname>, <varname>CapabilityBoundingSet</varname>,
      <varname>MountFlags</varname> also correspond to the configured settings of the unit files, but are
      encoded as the actual binary flag fields they are, rather than formatted as string.</para>

      <para><varname>ExecMainStartTimestamp</varname>, <varname>ExecMainStartTimestampMonotonic</varname>,
      <varname>ExecMainExitTimestamp</varname>, <varname>ExecMainExitTimestampMonotonic</varname>,
      <varname>ExecMainPID</varname>, <varname>ExecMainCode</varname>, <varname>ExecMainStatus</varname>
      contain information about the main process of the service as far as it is known. This is often the same
      runtime information that is stored in <varname>ExecStart</varname>. However, it deviates for
      <varname>Type=forking</varname> services where the main process of the service is not forked off
      systemd directly. These fields either contain information of the last run of the process or of the
      current running process.</para>

      <para><varname>MainPID</varname> and <varname>ControlPID</varname> contain the main and control PID of
      the service. The main PID is the current main PID of the service and is 0 when the service currently
      has no main PID. The control PID is the PID of the current start/stop/reload process running and is 0
      if no such process is currently running. That means that <varname>ExecMainPID</varname> and
      <varname>MainPID</varname> differ in the way that the latter immediately reflects whether a main
      process is currently running while the latter possible contains information collected from the last run
      even if the process is no longer around.</para>

      <para><varname>StatusText</varname> contains the status text passed to the service manager via a call
      to
      <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
      This may be used by services to inform the service manager about its internal state with a nice
      explanatory string.</para>

      <para><varname>Result</varname> encodes the execution result of the last run of the service. It is
      useful to determine the reason a service failed if it is in <literal>failed</literal> state (see
      <varname>ActiveState</varname> above). The following values are currently known:
      <literal>success</literal> is set if the unit didn't fail. <literal>resources</literal> indicates that
      not enough resources have been available to fork off and execute the service
      processes. <literal>timeout</literal> indicates that a time-out occurred while executing a service
      operation. <literal>exit-code</literal> indicates that a service process exited with an unclean exit
      code. <literal>signal</literal> indicates that a service process exited with an uncaught
      signal. <literal>core-dump</literal> indicates that a service process exited uncleanly and dumped
      core. <literal>watchdog</literal> indicates that a service did not send out watchdog ping messages
      often enough. <literal>start-limit</literal> indicates that a service has been started too frequently
      in a time frame (as configured in <varname>StartLimitInterval</varname>,
      <varname>StartLimitBurst</varname>).</para>

      <para><varname>ControlGroup</varname> indicates the control group path the processes of this service
      unit are placed in.</para>
    </refsect2>
  </refsect1>

  <refsect1>
    <title>Socket Unit Objects</title>

    <programlisting interface="org.freedesktop.systemd1.Socket">
$ gdbus introspect --system --dest org.freedesktop.systemd1 \
      --object-path /org/freedesktop/systemd1/unit/avahi_2ddaemon_2esocket

node /org/freedesktop/systemd1/unit/avahi_2ddaemon_2esocket {
  interface org.freedesktop.systemd1.Unit {
    ...
  };
  interface org.freedesktop.systemd1.Socket {
    methods:
    signals:
    properties:
      readonly b BindIPv6Only = 'default';
      readonly u Backlog = 128;
      readonly t TimeoutUSec = 90000000;
      readonly s Slice = 'system.slice';
      readonly s ControlGroup = '/system.slice/avahi-daemon.socket';
      readonly a(sasbttuii) ExecStartPre = [];
      readonly a(sasbttuii) ExecStartPost = [];
      readonly a(sasbttuii) ExecStopPre = [];
      readonly a(sasbttuii) ExecStopPost = [];
      readonly as Environment = [];
      readonly a(sb) EnvironmentFiles = [];
      readonly u UMask = 18;
      readonly t LimitCPU = 18446744073709551615;
      readonly t LimitFSIZE = 18446744073709551615;
      readonly t LimitDATA = 18446744073709551615;
      readonly t LimitSTACK = 18446744073709551615;
      readonly t LimitCORE = 18446744073709551615;
      readonly t LimitRSS = 18446744073709551615;
      readonly t LimitNOFILE = 4096;
      readonly t LimitAS = 18446744073709551615;
      readonly t LimitNPROC = 61434;
      readonly t LimitMEMLOCK = 65536;
      readonly t LimitLOCKS = 18446744073709551615;
      readonly t LimitSIGPENDING = 61434;
      readonly t LimitMSGQUEUE = 819200;
      readonly t LimitNICE = 0;
      readonly t LimitRTPRIO = 0;
      readonly t LimitRTTIME = 18446744073709551615;
      readonly s WorkingDirectory = '';
      readonly s RootDirectory = '';
      readonly i OOMScoreAdjust = 0;
      readonly i Nice = 0;
      readonly i IOScheduling = 0;
      readonly i CPUSchedulingPolicy = 0;
      readonly i CPUSchedulingPriority = 0;
      readonly ay CPUAffinity = [];
      readonly t TimerSlackNSec = 50000;
      readonly b CPUSchedulingResetOnFork = false;
      readonly b NonBlocking = false;
      readonly s StandardInput = 'null';
      readonly s StandardOutput = 'journal';
      readonly s StandardError = 'inherit';
      readonly s TTYPath = '';
      readonly b TTYReset = false;
      readonly b TTYVHangup = false;
      readonly b TTYVTDisallocate = false;
      readonly i SyslogPriority = 30;
      readonly s SyslogIdentifier = '';
      readonly b SyslogLevelPrefix = true;
      readonly s Capabilities = '';
      readonly i SecureBits = 0;
      readonly t CapabilityBoundingSet = 18446744073709551615;
      readonly s User = '';
      readonly s Group = '';
      readonly as SupplementaryGroups = [];
      readonly s TCPWrapName = '';
      readonly s PAMName = '';
      readonly as ReadWriteDirectories = [];
      readonly as ReadOnlyDirectories = [];
      readonly as InaccessibleDirectories = [];
      readonly t MountFlags = 0;
      readonly b PrivateTmp = false;
      readonly b PrivateNetwork = false;
      readonly b SameProcessGroup = false;
      readonly s UtmpIdentifier = '';
      readonly b IgnoreSIGPIPE = true;
      readonly b NoNewPrivileges = false;
      readonly au SystemCallFilter = [];
      readonly s KillMode = 'control-group';
      readonly i KillSignal = 15;
      readonly b SendSIGKILL = true;
      readonly b SendSIGHUP = false;
      readonly b CPUAccounting = false;
      readonly t CPUShares = 1024;
      readonly b BlockIOAccounting = false;
      readonly t BlockIOWeight = 1000;
      readonly a(st) BlockIODeviceWeight = [];
      readonly a(st) BlockIOReadBandwidth=;
      readonly a(st) BlockIOWriteBandwidth=;
      readonly b MemoryAccounting = false;
      readonly t MemoryLimit = 18446744073709551615;
      readonly s DevicePolicy = 'auto';
      readonly a(ss) DeviceAllow = [];
      readonly u ControlPID = 0;
      readonly s BindToDevice = '';
      readonly u DirectoryMode = 493;
      readonly u SocketMode = 438;
      readonly b Accept = false;
      readonly b KeepAlive = false;
      readonly i Priority = -1;
      readonly t ReceiveBuffer = 0;
      readonly t SendBuffer = 0;
      readonly i IPTOS = -1;
      readonly i IPTTL = -1;
      readonly t PipeSize = 0;
      readonly b FreeBind = false;
      readonly b Transparent = false;
      readonly b Broadcast = false;
      readonly b PassCredentials = false;
      readonly b PassSecurity = false;
      readonly i Mark = -1;
      readonly u MaxConnections = 64;
      readonly u NAccepted = 0;
      readonly u NConnections = 0;
      readonly x MessageQueueMaxMessages = 0;
      readonly x MessageQueueMessageSize = 0;
      readonly a(ss) Listen = [('Stream', '/var/run/avahi-daemon/socket')];
      readonly s Result = 'success';
      readonly b ReusePort = false;
      readonly s SmackLabel = '';
      readonly s SmackLabelIPIn = '';
      readonly s SmackLabelIPOut = '';
  };
  interface org.freedesktop.DBus.Properties {
    ...
  };
  interface org.freedesktop.DBus.Peer {
    ...
  };
  interface org.freedesktop.DBus.Introspectable {
    ...
  };
};
    </programlisting>

    <refsect2>
      <title>Properties</title>

      <para>Most of the properties map directly to the corresponding settings in socket unit files. As socket
      units can include <varname>ExecStartPre</varname> (and similar) fields which contain information about
      processes to execute. They also share most of the fields related to the execution context that Service
      objects expose (see above).</para>

      <para>In addition to these properties there are the following:</para>

      <para><varname>NAccepted</varname> contains the accumulated number of connections ever accepted on this
      socket. This only applies to sockets with <varname>Accept</varname> set to <literal>true</literal>,
      i.e. those where systemd is responsible for accepted connections. </para>

      <para>Similarly <varname>NConnections</varname> contains the number of currently open connections on
      this socket, and also applies only to socket with <varname>Accept</varname> set to
      <literal>true</literal>.</para>

      <para><varname>Result</varname> encodes the reason why a socket unit failed if it is in
      <literal>failed</literal> state (see <varname>ActiveState</varname> above). The values
      <literal>success</literal>, <literal>resources</literal>, <literal>timeout</literal>,
      <literal>exit-code</literal>, <literal>signal</literal> and <literal>core-dump</literal> have the same
      meaning as they have for the corresponding field of service units (see above). In addition to that the
      value <literal>service-failed-permanent</literal> indicates that the service of this socket failed
      continuously.</para>
    </refsect2>
  </refsect1>

  <refsect1>
    <title>Target Unit Objects</title>

    <programlisting interface="org.freedesktop.systemd1.Target">
$ gdbus introspect --system --dest org.freedesktop.systemd1 \
      --object-path /org/freedesktop/systemd1/unit/basic_2etarget

node /org/freedesktop/systemd1/unit/basic_2etarget {
  interface org.freedesktop.systemd1.Unit {
    ...
  };
  interface org.freedesktop.systemd1.Target {
    methods:
    signals:
    properties:
  };
  interface org.freedesktop.DBus.Properties {
    ...
  };
  interface org.freedesktop.DBus.Peer {
    ...
  };
  interface org.freedesktop.DBus.Introspectable {
    ...
  };
};
    </programlisting>

    <para>Target units have neither type-specific methods nor properties.</para>
  </refsect1>


  <refsect1>
    <title>Device Unit Objects</title>

    <para>All device unit objects implement the <interfacename>org.freedesktop.systemd1.Device</interfacename> interface (described here)
    in addition to the generic <interfacename>org.freedesktop.systemd1.Unit</interfacename> interface (see above).</para>

    <programlisting interface="org.freedesktop.systemd1.Device">
$ gdbus introspect --system --dest org.freedesktop.systemd1 \
      --object-path /org/freedesktop/systemd1/unit/dev_2dfoo_2edevice

node /org/freedesktop/systemd1/unit/dev_2d_foo_2edevice {
  interface org.freedesktop.systemd1.Unit {
    ...
  };
  interface org.freedesktop.systemd1.Device {
    methods:
    signals:
    properties:
      readonly s SysFSPath = '/sys/devices/pci0000:00/0000:00:1f.2/ata2/host1/target1:0:0/1:0:0:0/block/sdb';
  };
  interface org.freedesktop.DBus.Properties {
    ...
  };
  interface org.freedesktop.DBus.Peer {
    ...
  };
  interface org.freedesktop.DBus.Introspectable {
    ...
  };
};
    </programlisting>

    <refsect2>
      <title>Properties</title>

      <para>Device units only expose a single type-specific property:</para>

      <para><varname>SysFSPath</varname> contains the sysfs path of the kernel device this object corresponds
      to.</para>
    </refsect2>
  </refsect1>


  <refsect1>
    <title>Mount Unit Objects</title>

    <para>All mount unit objects implement the <interfacename>org.freedesktop.systemd1.Mount</interfacename>
    interface (described here) in addition to the generic
    <interfacename>org.freedesktop.systemd1.Unit</interfacename> interface (see above)</para>

    <programlisting interface="org.freedesktop.systemd1.Mount">
$ gdbus introspect --system --dest org.freedesktop.systemd1 \
      --object-path /org/freedesktop/systemd1/unit/home_2emount

node /org/freedesktop/systemd1/unit/home_2emount {
  interface org.freedesktop.systemd1.Unit {
    ...
  };
  interface org.freedesktop.systemd1.Mount {
    methods:
    signals:
    properties:
      readonly s Where = '/home';
      readonly s What = '/dev/mapper/home';
      readonly s Options = 'rw,relatime,rw,seclabel,data=ordered';
      readonly s Type = 'ext4';
      readonly t TimeoutUSec = 90000000;
      readonly s Slice = 'system.slice';
      readonly s ControlGroup = '/system.slice/home.mount';
      readonly a(sasbttuii) ExecMount = [('/bin/mount', ['/bin/mount', '/dev/disk/by-uuid/59a54df8-d070-4907-a4a7-2e0ce05d5c2a', '/home', '-t', 'ext4'], false, 1357656124168977, 11158027, 1357656124274805, 11263855, 608, 1, 0)];
      readonly a(sasbttuii) ExecUnmount = [];
      readonly a(sasbttuii) ExecRemount = [];
      readonly as Environment = [];
      readonly a(sb) EnvironmentFiles = [];
      readonly u UMask = 18;
      readonly t LimitCPU = 18446744073709551615;
      readonly t LimitFSIZE = 18446744073709551615;
      readonly t LimitDATA = 18446744073709551615;
      readonly t LimitSTACK = 18446744073709551615;
      readonly t LimitCORE = 18446744073709551615;
      readonly t LimitRSS = 18446744073709551615;
      readonly t LimitNOFILE = 4096;
      readonly t LimitAS = 18446744073709551615;
      readonly t LimitNPROC = 61434;
      readonly t LimitMEMLOCK = 65536;
      readonly t LimitLOCKS = 18446744073709551615;
      readonly t LimitSIGPENDING = 61434;
      readonly t LimitMSGQUEUE = 819200;
      readonly t LimitNICE = 0;
      readonly t LimitRTPRIO = 0;
      readonly t LimitRTTIME = 18446744073709551615;
      readonly s WorkingDirectory = '';
      readonly s RootDirectory = '';
      readonly i OOMScoreAdjust = 0;
      readonly i Nice = 0;
      readonly i IOScheduling = 0;
      readonly i CPUSchedulingPolicy = 0;
      readonly i CPUSchedulingPriority = 0;
      readonly ay CPUAffinity = [];
      readonly t TimerSlackNSec = 50000;
      readonly b CPUSchedulingResetOnFork = false;
      readonly b NonBlocking = false;
      readonly s StandardInput = 'null';
      readonly s StandardOutput = 'journal';
      readonly s StandardError = 'inherit';
      readonly s TTYPath = '';
      readonly b TTYReset = false;
      readonly b TTYVHangup = false;
      readonly b TTYVTDisallocate = false;
      readonly i SyslogPriority = 30;
      readonly s SyslogIdentifier = '';
      readonly b SyslogLevelPrefix = true;
      readonly s Capabilities = '';
      readonly i SecureBits = 0;
      readonly t CapabilityBoundingSet = 18446744073709551615;
      readonly s User = '';
      readonly s Group = '';
      readonly as SupplementaryGroups = [];
      readonly s TCPWrapName = '';
      readonly s PAMName = '';
      readonly as ReadWriteDirectories = [];
      readonly as ReadOnlyDirectories = [];
      readonly as InaccessibleDirectories = [];
      readonly t MountFlags = 0;
      readonly b PrivateTmp = false;
      readonly b PrivateNetwork = false;
      readonly b SameProcessGroup = true;
      readonly s UtmpIdentifier = '';
      readonly b IgnoreSIGPIPE = true;
      readonly b NoNewPrivileges = false;
      readonly au SystemCallFilter = [];
      readonly s KillMode = 'control-group';
      readonly i KillSignal = 15;
      readonly b SendSIGKILL = true;
      readonly b SendSIGHUP = false;
      readonly b CPUAccounting = false;
      readonly t CPUShares = 1024;
      readonly b BlockIOAccounting = false;
      readonly t BlockIOWeight = 1000;
      readonly a(st) BlockIODeviceWeight = [];
      readonly a(st) BlockIOReadBandwidth=;
      readonly a(st) BlockIOWriteBandwidth=;
      readonly b MemoryAccounting = false;
      readonly t MemoryLimit = 18446744073709551615;
      readonly s DevicePolicy = 'auto';
      readonly a(ss) DeviceAllow = [];
      readonly u ControlPID = 0;
      readonly u DirectoryMode = 493;
      readonly s Result = 'success';
  };
  interface org.freedesktop.DBus.Properties {
    ...
  };
  interface org.freedesktop.DBus.Peer {
    ...
  };
  interface org.freedesktop.DBus.Introspectable {
    ...
  };
};
    </programlisting>

    <refsect2>
      <title>Properties</title>

      <para>Most of the properties map directly to the corresponding settings in mount unit files. As mount
      units invoke the <filename>/usr/bin/mount</filename> command their bus objects include implicit
      <varname>ExecMount</varname> (and similar) fields which contain information about processes to
      execute. They also share most of the fields related to the execution context that Service objects
      expose (see above). In addition to these properties there are the following:</para>

      <para><varname>ControlPID</varname> contains the PID of the currently running
      <filename>/usr/bin/mount</filename> or <filename>/usr/bin/umount</filename> command if there is one
      running, otherwise 0.</para>

      <para><varname>Result</varname> contains a value explaining why a mount unit failed if it failed. It
      can take the values <literal>success</literal>, <literal>resources</literal>,
      <literal>timeout</literal>, <literal>exit-code</literal>, <literal>signal</literal>,
      <literal>core-dump</literal> which have the identical meaning as the corresponding values of the
      corresponding field of service unit objects (see above).</para>
    </refsect2>
  </refsect1>

  <refsect1>
    <title>Automount Unit Objects</title>

    <para>All automount unit objects implement the
    <interfacename>org.freedesktop.systemd1.Automount</interfacename> interface (described here) in addition
    to the generic <interfacename>org.freedesktop.systemd1.Unit</interfacename> interface (see above).</para>

    <programlisting interface="org.freedesktop.systemd1.Automount">
$ gdbus introspect --system --dest org.freedesktop.systemd1 \
      --object-path /org/freedesktop/systemd1/unit/proc_2dsys_2dfs_2dbinfmt_5fmisc_2eautomount

node /org/freedesktop/systemd1/unit/proc_2dsys_2dfs_2dbinfmt_5fmisc_2eautomount {
  interface org.freedesktop.systemd1.Unit {
    ...
  };
  interface org.freedesktop.systemd1.Automount {
    methods:
    signals:
    properties:
      readonly s Where = '/proc/sys/fs/binfmt_misc';
      readonly u DirectoryMode = 493;
      readonly s Result = 'success';
  };
  interface org.freedesktop.DBus.Properties {
    ...
  };
  interface org.freedesktop.DBus.Peer {
    ...
  };
  interface org.freedesktop.DBus.Introspectable {
    ...
  };
};
    </programlisting>

    <refsect2>
      <title>Properties</title>

      <para>Most of the properties map directly to the corresponding settings in the automount unit
      files.</para>

      <para><varname>Result</varname> knows the values <literal>success</literal> and
      <literal>resources</literal>, at this time. They have the same meanings as the corresponding values of
      the corresponding field of the Service object.</para>
    </refsect2>
  </refsect1>


  <refsect1>
    <title>Timer Unit Objects</title>

    <para>All timer unit objects implement the <interfacename>org.freedesktop.systemd1.Timer</interfacename>
    interface (described here) in addition to the generic
    <interfacename>org.freedesktop.systemd1.Unit</interfacename> interface (see above).</para>

    <programlisting interface="org.freedesktop.systemd1.Timer">
$ gdbus introspect --system --dest org.freedesktop.systemd1 \
      --object-path /org/freedesktop/systemd1/unit/systemd_2dtmpfiles_2dclean_2etimer

node /org/freedesktop/systemd1/unit/systemd_2dtmpfiles_2dclean_2etimer {
  interface org.freedesktop.systemd1.Unit {
    ...
  };
  interface org.freedesktop.systemd1.Timer {
      readonly s Unit = 'systemd-tmpfiles-clean.service';
      readonly a(stt) TimersMonotonic = [('OnUnitActiveUSec', 86400000000, 173700033104), ('OnBootUSec', 900000000, 900000000)];
      readonly a(sst) TimersCalendar = [];
      readonly t NextElapseUSecRealtime = 0;
      readonly t NextElapseUSecMonotonic = 173700033104;
      readonly s Result = 'success';
  };
  interface org.freedesktop.DBus.Properties {
    ...
  };
  interface org.freedesktop.DBus.Peer {
    ...
  };
  interface org.freedesktop.DBus.Introspectable {
    ...
  };
};
    </programlisting>

    <refsect2>
      <title>Properties</title>

      <para><varname>Unit</varname> contains the name of the unit to activate when the timer elapses.</para>

      <para><varname>TimersMonotonic</varname> contains an array of structs that contain information about
      all monotonic timers of this timer unit. The structs contain a string identifying the timer base, which
      is one of <literal>OnActiveUSec</literal>, <literal>OnBootUSec</literal>,
      <literal>OnStartupUSec</literal>, <literal>OnUnitActiveUSec</literal>,
      <literal>OnUnitInactiveUSec</literal>, which correspond to the settings of the same names in the timer
      unit files; the microsecond offset from this timer base in monotonic time; the next elapsation point on
      the <constant>CLOCK_MONOTONIC</constant> clock, relative its epoch.</para>

      <para><varname>TimersCalendar</varname> contains an array of structs that contain information about all
      realtime/calendar timers of this timer unit. The structs contain a string identifying the timer base,
      which may only be <literal>OnCalendar</literal> for now; the calendar specification string; the next
      elapsation point on the <constant>CLOCK_REALTIME</constant> clock, relative to its epoch.</para>

      <para><varname>NextElapseUSecRealtime</varname> contains the next elapsation point on the
      <constant>CLOCK_REALTIME</constant> clock in miscroseconds since the epoch, or 0 if this timer event
      does not include at least one calendar event.</para>

      <para>Similarly, <varname>NextElapseUSecMonotonic</varname> contains the next elapsation point on the
      <constant>CLOCK_MONOTONIC</constant> clock in microseconds since the epoch, or 0 if this timer event
      does not include at least one monotonic event.</para>

      <para><varname>Result</varname> knows the values <literal>success</literal> and
      <literal>resources</literal> with the same meanings as the matching values of the corresponding
      property of the service interface.</para>
    </refsect2>
  </refsect1>

  <refsect1>
    <title>Swap Unit Objects</title>

    <para>All swap unit objects implement the <interfacename>org.freedesktop.systemd1.Swap</interfacename>
    interface (described here) in addition to the generic
    <interfacename>org.freedesktop.systemd1.Unit</interfacename> interface (see above).</para>

    <programlisting interface="org.freedesktop.systemd1.Swap">
$ gdbus introspect --system --dest org.freedesktop.systemd1 \
      --object-path /org/freedesktop/systemd1/unit/dev_2dsda3_2eswap

node /org/freedesktop/systemd1/unit/dev_2dsda3_2eswap {
  interface org.freedesktop.systemd1.Unit {
    ...
  };
  interface org.freedesktop.systemd1.Swap {
    methods:
    signals:
    properties:
      readonly s What = '/dev/sda3';
      readonly i Priority = -1;
      readonly t TimeoutUSec = 90000000;
      readonly s Slice = 'system.slice';
      readonly s ControlGroup = '';
      readonly a(sasbttuii) ExecActivate = [];
      readonly a(sasbttuii) ExecDeactivate = [];
      readonly as Environment = [];
      readonly a(sb) EnvironmentFiles = [];
      readonly u UMask = 18;
      readonly t LimitCPU = 18446744073709551615;
      readonly t LimitFSIZE = 18446744073709551615;
      readonly t LimitDATA = 18446744073709551615;
      readonly t LimitSTACK = 18446744073709551615;
      readonly t LimitCORE = 18446744073709551615;
      readonly t LimitRSS = 18446744073709551615;
      readonly t LimitNOFILE = 4096;
      readonly t LimitAS = 18446744073709551615;
      readonly t LimitNPROC = 61434;
      readonly t LimitMEMLOCK = 65536;
      readonly t LimitLOCKS = 18446744073709551615;
      readonly t LimitSIGPENDING = 61434;
      readonly t LimitMSGQUEUE = 819200;
      readonly t LimitNICE = 0;
      readonly t LimitRTPRIO = 0;
      readonly t LimitRTTIME = 18446744073709551615;
      readonly s WorkingDirectory = '';
      readonly s RootDirectory = '';
      readonly i OOMScoreAdjust = 0;
      readonly i Nice = 0;
      readonly i IOScheduling = 0;
      readonly i CPUSchedulingPolicy = 0;
      readonly i CPUSchedulingPriority = 0;
      readonly ay CPUAffinity = [];
      readonly t TimerSlackNS = 50000;
      readonly b CPUSchedulingResetOnFork = false;
      readonly b NonBlocking = false;
      readonly s StandardInput = 'null';
      readonly s StandardOutput = 'journal';
      readonly s StandardError = 'inherit';
      readonly s TTYPath = '';
      readonly b TTYReset = false;
      readonly b TTYVHangup = false;
      readonly b TTYVTDisallocate = false;
      readonly i SyslogPriority = 30;
      readonly s SyslogIdentifier = '';
      readonly b SyslogLevelPrefix = true;
      readonly s Capabilities = '';
      readonly i SecureBits = 0;
      readonly t CapabilityBoundingSet = 18446744073709551615;
      readonly s User = '';
      readonly s Group = '';
      readonly as SupplementaryGroups = [];
      readonly s TCPWrapName = '';
      readonly s PAMName = '';
      readonly as ReadWriteDirectories = [];
      readonly as ReadOnlyDirectories = [];
      readonly as InaccessibleDirectories = [];
      readonly t MountFlags = 0;
      readonly b PrivateTmp = false;
      readonly b PrivateNetwork = false;
      readonly b SameProcessGroup = false;
      readonly s KillMode = 'control-group';
      readonly i KillSignal = 15;
      readonly s UtmpIdentifier = '';
      readonly b IgnoreSIGPIPE = true;
      readonly b NoNewPrivileges = false;
      readonly au SystemCallFilter = [];
      readonly s KillMode = 'control-group';
      readonly i KillSignal = 15;
      readonly b SendSIGKILL = true;
      readonly b SendSIGHUP = false;
      readonly b CPUAccounting = false;
      readonly t CPUShares = 1024;
      readonly b BlockIOAccounting = false;
      readonly t BlockIOWeight = 1000;
      readonly a(st) BlockIODeviceWeight = [];
      readonly a(st) BlockIOReadBandwidth=;
      readonly a(st) BlockIOWriteBandwidth=;
      readonly b MemoryAccounting = false;
      readonly t MemoryLimit = 18446744073709551615;
      readonly s DevicePolicy = 'auto';
      readonly a(ss) DeviceAllow = [];
      readonly u ControlPID = 0;
      readonly s Result = 'success';
  };
  interface org.freedesktop.DBus.Properties {
    ...
  };
  interface org.freedesktop.DBus.Peer {
    ...
  };
  interface org.freedesktop.DBus.Introspectable {
    ...
  };
};
    </programlisting>

    <refsect2>
      <title>Properties</title>

      <para>Most of the properties map directly to the corresponding settings in swap unit files. As mount
      units invoke the
      <citerefentry><refentrytitle>swapon</refentrytitle><manvolnum>8</manvolnum></citerefentry> command
      their bus objects include implicit <varname>ExecActivate</varname> (and similar) fields which contain
      information about processes to execute. They also share most of the fields related to the execution
      context that Service objects expose (see above). In addition to these properties there are the
      following:</para>

      <para><varname>ControlPID</varname> contains the PID of the currently running
      <citerefentry><refentrytitle>swapon</refentrytitle><manvolnum>8</manvolnum></citerefentry> or
      <citerefentry><refentrytitle>swapoff</refentrytitle><manvolnum>8</manvolnum></citerefentry> command if
      there is one running, otherwise 0.</para>

      <para><varname>Result</varname> contains a value explaining why a mount unit failed if it failed. It
      can take the values <literal>success</literal>, <literal>resources</literal>,
      <literal>timeout</literal>, <literal>exit-code</literal>, <literal>signal</literal>,
      <literal>core-dump</literal> which have the identical meanings as the corresponding values of the
      corresponding field of service unit objects (see above).</para>
    </refsect2>
  </refsect1>


  <refsect1>
    <title>Path Unit Objects</title>

    <programlisting interface="org.freedesktop.systemd1.Path">
$ gdbus introspect --system --dest org.freedesktop.systemd1 \
      --object-path /org/freedesktop/systemd1/unit/cups_2epath

node /org/freedesktop/systemd1/unit/cups_2epath {
  interface org.freedesktop.systemd1.Unit {
    ...
  };
  interface org.freedesktop.systemd1.Path {
    methods:
    signals:
    properties:
      readonly s Unit = 'cups.service';
      readonly a(ss) Paths = [('PathExistsGlob', '/var/spool/cups/d*')];
      readonly b MakeDirectory = false;
      readonly u DirectoryMode = 493;
      readonly s Result = 'success';
  };
  interface org.freedesktop.DBus.Properties {
    ...
  };
  interface org.freedesktop.DBus.Peer {
    ...
  };
  interface org.freedesktop.DBus.Introspectable {
    ...
  };
};
    </programlisting>

    <refsect2>
      <title>Properties</title>

      <para>Most properties correspond directly with the matching settings in path unit files.</para>

      <para>The others:</para>

      <para><varname>Paths</varname> contains an array of structs. Each struct contains the condition to
      watch, which can be one of <literal>PathExists</literal>, <literal>PathExistsGlob</literal>,
      <literal>PathChanged</literal>, <literal>PathModified</literal>, <literal>DirectoryNotEmpty</literal>
      which correspond directly to the matching settings in the path unit files; and the path to watch,
      possibly including glob expressions.</para>

      <para><varname>Result</varname> contains a result value which can be <literal>success</literal> or
      <literal>resources</literal>, which have the same meaning as the corresponding field of the service
      interface.</para>
    </refsect2>
  </refsect1>

  <refsect1>
    <title>Slice Unit Objects</title>

    <para>All slice unit objects implement the <interfacename>org.freedesktop.systemd1.Slice</interfacename>
    interface (described here) in addition to the generic
    <interfacename>org.freedesktop.systemd1.Unit</interfacename> interface (see above).</para>

    <programlisting interface="org.freedesktop.systemd1.Slice">
$ gdbus introspect --system --dest org.freedesktop.systemd1 \
      --object-path /org/freedesktop/systemd1/unit/system_2eslice

node /org/freedesktop/systemd1/unit/system_2eslice {
  interface org.freedesktop.systemd1.Unit {
    ...
  };
  interface org.freedesktop.systemd1.Slice {
    methods:
    signals:
    properties:
      readonly s Slice = '-.slice';
      readonly s ControlGroup = '/system.slice';
      readonly b CPUAccounting = false;
      readonly t CPUShares = 1024;
      readonly b BlockIOAccounting = false;
      readonly t BlockIOWeight = 1000;
      readonly a(st) BlockIODeviceWeight = [];
      readonly a(st) BlockIOReadBandwidth=;
      readonly a(st) BlockIOWriteBandwidth=;
      readonly b MemoryAccounting = false;
      readonly t MemoryLimit = 18446744073709551615;
      readonly s DevicePolicy = 'auto';
      readonly a(ss) DeviceAllow = [];
  };
  interface org.freedesktop.DBus.Properties {
    ...
  };
  interface org.freedesktop.DBus.Peer {
    ...
  };
  interface org.freedesktop.DBus.Introspectable {
    ...
  };
};
    </programlisting>

    <refsect2>
      <title>Properties</title>

      <para>Most properties correspond directly with the matching settings in slice unit files.</para>
    </refsect2>
  </refsect1>

  <refsect1>
    <title>Scope Unit Objects</title>

    <para>All slice unit objects implement the <interfacename>org.freedesktop.systemd1.Scope</interfacename>
    interface (described here) in addition to the generic
    <interfacename>org.freedesktop.systemd1.Unit</interfacename> interface (see above).</para>

    <programlisting interface="org.freedesktop.systemd1.Scope">
$ gdbus introspect --system --dest org.freedesktop.systemd1 \
      --object-path /org/freedesktop/systemd1/unit/session_2d1_2escope

node /org/freedesktop/systemd1/unit/session_2d1_2escope {
  interface org.freedesktop.systemd1.Unit {
    ...
  };
  interface org.freedesktop.systemd1.Scope {
    methods:
      Abandon();
    signals:
      RequestStop();
    properties:
      readonly s Slice = 'user-1000.slice';
      readonly s ControlGroup = '/user.slice/user-1000.slice/session-1.scope';
      readonly t TimeoutStopUSec = 500000;
      readonly s KillMode = 'none';
      readonly i KillSignal = 15;
      readonly b SendSIGKILL = true;
      readonly b SendSIGHUP = true;
      readonly b CPUAccounting = false;
      readonly t CPUShares = 1024;
      readonly b BlockIOAccounting = false;
      readonly t BlockIOWeight = 1000;
      readonly a(st) BlockIODeviceWeight = [];
      readonly a(st) BlockIOReadBandwidth=;
      readonly a(st) BlockIOWriteBandwidth=;
      readonly b MemoryAccounting = false;
      readonly t MemoryLimit = 18446744073709551615;
      readonly s DevicePolicy = 'auto';
      readonly a(ss) DeviceAllow = [];
      readonly s Result = 'success';
      readonly s Controller = '';


  };
  interface org.freedesktop.DBus.Properties {
    ...
  };
  interface org.freedesktop.DBus.Peer {
    ...
  };
  interface org.freedesktop.DBus.Introspectable {
    ...
  };
};
    </programlisting>

    <refsect2>
      <title>Methods</title>

      <para><function>Abandon()</function> may be used to place a scope unit in the "abandoned" state. This
      may be used to inform the system manager that the manager that created the scope lost interest in the
      scope (for example, because it is terminating), without wanting to shut down the scope entirely</para>
    </refsect2>

    <refsect2>
      <title>Signals</title>

      <para><function>RequestStop</function> is sent to the peer that is configured in the
      <varname>Controller</varname> property when systemd is requested to terminate the scope unit. A program
      registering a scope can use this to cleanly shut down the processes it added to the scope, instead of
      letting systemd do it with the usual <constant>SIGTERM</constant> logic.</para>
    </refsect2>

    <refsect2>
      <title>Properties</title>

      <para>All properties correspond directly with the matching properties of service units</para>

      <para><varname>Controller</varname> contains the bus name (unique or well-known) that is notified when
      the scope unit is to be shut down via a <function>RequestStop</function> signal (see below). This is
      set when the scope is created. If not set the scope's processes will terminated with
      <constant>SIGTERM</constant> directly.</para>
    </refsect2>
  </refsect1>


  <refsect1>
    <title>Job Objects</title>

    <para>Job objects encapsulate scheduled or running jobs. Each unit can have none or one jobs in the
    execution queue. Each job is attached to exactly one unit.</para>

    <programlisting>
$ gdbus introspect --system --dest org.freedesktop.systemd1 \
      --object-path /org/freedesktop/systemd1/job/1292

node /org/freedesktop/systemd1/job/1292 {
  interface org.freedesktop.systemd1.Job {
    methods:
      Cancel();
    signals:
    properties:
      readonly u Id = 1292;
      readonly (so) Unit = ('slow.service', '/org/freedesktop/systemd1/unit/slow_2eservice');
      readonly s JobType = 'start';
      readonly s State = 'running';
  };
  interface org.freedesktop.DBus.Properties {
    ...
  };
  interface org.freedesktop.DBus.Peer {
    ...
  };
  interface org.freedesktop.DBus.Introspectable {
    ...
  };
};
    </programlisting>

    <refsect2>
      <title>Methods</title>

      <para><function>Cancel()</function> cancels the job. Note that this will remove a job from the queue if
      it is not yet executed but generally will not cause a job that is already in the process of being
      executed to be aborted. This operation may also be requested via the <function>CancelJob()</function>
      method of the Manager object (see above), which is sometimes useful to reduce roundtrips.</para>
    </refsect2>

    <refsect2>
      <title>Properties</title>

      <para><varname>Id</varname> is the numeric Id of the job. During the runtime of a systemd instance each
      numeric ID is only assigned once.</para>

      <para><varname>Unit</varname> refers to the unit this job belongs two. It is a structure consisting of
      the name of the unit and a bus path to the unit's object.</para>

      <para><varname>JobType</varname> refers to the job's type and is one of <literal>start</literal>,
      <literal>verify-active</literal>, <literal>stop</literal>, <literal>reload</literal>,
      <literal>restart</literal>, <literal>try-restart</literal>, <literal>reload-or-start</literal>. Note
      that later versions might define additional values.</para>

      <para><varname>State</varname> refers to the job's state and is one of <literal>waiting</literal> and
      <literal>running</literal>. The former indicates that a job is currently queued but has not begun to
      execute yet, the latter indicates that a job is currently being executed.</para>
    </refsect2>
  </refsect1>

  <refsect1>
    <title>Versioning</title>

    <para>These D-Bus interfaces follow <ulink url="http://0pointer.de/blog/projects/versioning-dbus.html">
    the usual interface versioning guidelines</ulink>.</para>
  </refsect1>
</refentry>