man/systemd-journald.service.xml

   1 <?xml version='1.0'?> <!--*-nxml-*-->
   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
   3         "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
   4
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   6   This file is part of systemd.
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   8   Copyright 2010 Lennart Poettering
   9
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  11   under the terms of the GNU Lesser General Public License as published by
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  23
  24 <refentry id="systemd-journald.service">
  25
  26         <refentryinfo>
  27                 <title>systemd-journald</title>
  28                 <productname>systemd</productname>
  29
  30                 <authorgroup>
  31                         <author>
  32                                 <contrib>Developer</contrib>
  33                                 <firstname>Lennart</firstname>
  34                                 <surname>Poettering</surname>
  35                                 <email>lennart@poettering.net</email>
  36                         </author>
  37                 </authorgroup>
  38         </refentryinfo>
  39
  40         <refmeta>
  41                 <refentrytitle>systemd-journald</refentrytitle>
  42                 <manvolnum>8</manvolnum>
  43         </refmeta>
  44
  45         <refnamediv>
  46                 <refname>systemd-journald.service</refname>
  47                 <refname>systemd-journald</refname>
  48                 <refpurpose>systemd Journal Service</refpurpose>
  49         </refnamediv>
  50
  51         <refsynopsisdiv>
  52                 <para><filename>systemd-journald.service</filename></para>
  53                 <para><filename>/usr/lib/systemd/systemd-journald</filename></para>
  54         </refsynopsisdiv>
  55
  56         <refsect1>
  57                 <title>Description</title>
  58
  59                 <para><filename>systemd-journald</filename> is a
  60                 system service that collects and stores logging
  61                 data. It creates and maintains structured, indexed
  62                 journals based on logging information that is received
  63                 from the kernel, from user processes via the libc
  64                 <citerefentry><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  65                 call, from STDOUT/STDERR of system services or via its
  66                 native API. It will implicitly collect numerous meta
  67                 data fields for each log messages in a secure and
  68                 unfakeable way. See
  69                 <citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>
  70                 for more information about the collected meta data.
  71                 </para>
  72
  73                 <para>Log data collected by the journal is primarily
  74                 text based but can also include binary data where
  75                 necessary. All objects stored in the journal can be up
  76                 to 2^64-1 bytes in size.</para>
  77
  78                 <para>By default the journal stores log data in
  79                 <filename>/run/log/journal/</filename>. Since
  80                 <filename>/run/</filename> is volatile log data is
  81                 lost at reboot. To make the data persistent it
  82                 is sufficient to create
  83                 <filename>/var/log/journal/</filename> where
  84                 <filename>systemd-journald</filename> will then store
  85                 the data.</para>
  86
  87                 <para><filename>systemd-journald</filename> will
  88                 forward all received log messages to the AF_UNIX
  89                 SOCK_DGRAM socket
  90                 <filename>/run/systemd/journal/syslog</filename> (if it exists) which
  91                 may be used by UNIX syslog daemons to process the data
  92                 further.</para>
  93
  94                 <para>See
  95                 <citerefentry><refentrytitle>journald.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>
  96                 for information about the configuration of this
  97                 service.</para>
  98         </refsect1>
  99
 100         <refsect1>
 101                 <title>Signals</title>
 102
 103                 <variablelist>
 104                         <varlistentry>
 105                                 <term>SIGUSR1</term>
 106
 107                                 <listitem><para>Request that journal
 108                                 data from <filename>/run/</filename>
 109                                 is flushed to
 110                                 <filename>/var/</filename> in order to
 111                                 make it persistent (if this is
 112                                 enabled). This may be used after
 113                                 <filename>/var/</filename> is mounted,
 114                                 but is generally not required since
 115                                 the first journal write when
 116                                 <filename>/var/</filename> becomes
 117                                 writable triggers the flushing
 118                                 anyway.</para></listitem>
 119                         </varlistentry>
 120
 121                         <varlistentry>
 122                                 <term>SIGUSR2</term>
 123
 124                                 <listitem><para>Request immediate
 125                                 rotation of the journal
 126                                 files.</para></listitem>
 127                         </varlistentry>
 128                 </variablelist>
 129         </refsect1>
 130
 131
 132
 133         <refsect1>
 134                 <title>See Also</title>
 135                 <para>
 136                         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 137                         <citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 138                         <citerefentry><refentrytitle>journald.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 139                         <citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 140                 </para>
 141         </refsect1>
 142
 143 </refentry>