source: BOOK/system-config/common/usage.xml @ 0d36d0a

clfs-3.0.0-systemdsystemd
Last change on this file since 0d36d0a was 0d36d0a, checked in by Chris Staub <chris@…>, 10 years ago

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1<?xml version="1.0" encoding="ISO-8859-1"?>
2<!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
3  "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
4  <!ENTITY % general-entities SYSTEM "../../general.ent">
5  %general-entities;
6]>
7
8<sect1 id="ch-config-usage">
9  <?dbhtml filename="usage.html"?>
10
11  <title>How does Systemd work?</title>
12
13  <indexterm zone="ch-config-usage">
14    <primary sortas="a-systemd">Systemd</primary>
15  <secondary>usage</secondary></indexterm>
16
17  <warning>
18    <para>Please disregard this page until it is complete and verified.</para>
19  </warning>
20
21  <sect2>
22    <title>Introduction to Systemd</title>
23
24
25    <para>Systemd is a system management daemon designed exclusively for the
26    Linux kernel API. In the Linux startup process, it is the first process to
27    execute in user land; therefore, it is also the parent process of all child
28    processes in user land.</para>
29
30    <para>Systemd's initialization instructions for each daemon are recorded in
31    a declarative configuration file rather than a shell script. For
32    inter-process communication, systemd makes Unix domain sockets and D-Bus
33    available to the running daemons. Because systemd tracks processes using
34    Linux cgroups instead of process identifiers (PIDs), daemons cannot "escape"
35    systemd; not even by double-forking. Systemd is also capable of aggressive
36    parallelization.</para>
37
38    <para>Among systemd's auxiliary features are a cron-like job scheduler
39    called systemd Calendar Timers, and an event logging subsystem called
40    journal. The system administrator may choose whether to log system events
41    with systemd or syslog. Systemd's logfile is a binary file. The state of
42    systemd itself can be preserved in a snapshot for future recall.</para>
43
44    <para>Systemd provides a replacement for sysvinit, pm-utils, inetd, acpid,
45    syslog, watchdog, cron and atd, and obsoletes ConsoleKit.</para>
46
47  </sect2>
48
49  <sect2>
50    <title>Systemctl</title>
51
52    <para><command>systemctl</command> is the main command used to introspect
53     and control systemd.</para>
54
55    <variablelist>
56
57      <varlistentry>
58        <term>List running units:</term>
59        <listitem>
60          <para><command>systemctl</command> or <command>systemctl list-units</command></para>
61        </listitem>
62      </varlistentry>
63
64      <varlistentry>
65        <term>List failed units:</term>
66        <listitem>
67          <para><command>systemctl --failed</command></para>
68        </listitem>
69      </varlistentry>
70
71      <varlistentry>
72        <term>List available unit files:</term>
73        <listitem>
74          <para><command>systemctl list-unit-files</command></para>
75        </listitem>
76      </varlistentry>
77
78      <varlistentry>
79        <term>Activate a unit immediately:</term>
80        <listitem>
81          <para><command>systemctl start</command> <replaceable>unit</replaceable></para>
82        </listitem>
83      </varlistentry>
84
85      <varlistentry>
86        <term>Stop a unit immediately:</term>
87        <listitem>
88          <para><command>systemctl stop </command><replaceable>unit</replaceable></para>
89        </listitem>
90      </varlistentry>
91
92      <varlistentry>
93        <term>Restart a unit:</term>
94        <listitem>
95          <para><command>systemctl restart </command><replaceable>unit</replaceable></para>
96        </listitem>
97      </varlistentry>
98
99      <varlistentry>
100        <term>Reload unit configuration:</term>
101        <listitem>
102          <para><command>systemctl reload </command><replaceable>unit</replaceable></para>
103        </listitem>
104      </varlistentry>
105
106      <varlistentry>
107        <term>Show status of a unit:</term>
108        <listitem>
109          <para><command>systemctl status </command><replaceable>unit</replaceable></para>
110        </listitem>
111      </varlistentry>
112
113      <varlistentry>
114        <term>Check if a unit is enabled or disabled:</term>
115        <listitem>
116          <para><command>systemctl is-enabled </command><replaceable>unit</replaceable></para>
117        </listitem>
118      </varlistentry>
119
120      <varlistentry>
121        <term>Enable a unit to start during boot:</term>
122        <listitem>
123          <para><command>systemctl enable </command><replaceable>unit</replaceable></para>
124        </listitem>
125      </varlistentry>
126
127      <varlistentry>
128        <term>Disable a unit to not start during boot:</term>
129        <listitem>
130          <para><command>systemctl disable </command><replaceable>unit</replaceable></para>
131        </listitem>
132      </varlistentry>
133
134      <varlistentry>
135        <term>Reload systemd and scan for new or changed units:</term>
136        <listitem>
137          <para><command>systemctl daemon-reload</command></para>
138        </listitem>
139      </varlistentry>
140
141    </variablelist>
142
143    <para>For more information regarding systemd, please refer to the systemd
144    and related man-pages and
145    <ulink url="https://fedoraproject.org/wiki/Systemd">Systemd at
146    FedoraProject</ulink> for documentation, examples, features, and other
147    information.</para>
148
149  </sect2>
150
151</sect1>
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