man/systemd-journald.service.xml

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  23
  24 <refentry id="systemd-journald.service">
  25
  26         <refentryinfo>
  27                 <title>systemd-journald.service</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.service</refentrytitle>
  42                 <manvolnum>8</manvolnum>
  43         </refmeta>
  44
  45         <refnamediv>
  46                 <refname>systemd-journald.service</refname>
  47                 <refname>systemd-journald.socket</refname>
  48                 <refname>systemd-journald</refname>
  49                 <refpurpose>systemd Journal Service</refpurpose>
  50         </refnamediv>
  51
  52         <refsynopsisdiv>
  53                 <para><filename>systemd-journald.service</filename></para>
  54                 <para><filename>systemd-journald.socket</filename></para>
  55                 <para><filename>/usr/lib/systemd/systemd-journald</filename></para>
  56         </refsynopsisdiv>
  57
  58         <refsect1>
  59                 <title>Description</title>
  60
  61                 <para><filename>systemd-journald</filename> is a
  62                 system service that collects and stores logging
  63                 data. It creates and maintains structured, indexed
  64                 journals based on logging information that is received
  65                 from the kernel, from user processes via the libc
  66                 <citerefentry><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  67                 call, from STDOUT/STDERR of system services or via its
  68                 native API. It will implicitly collect numerous meta
  69                 data fields for each log messages in a secure and
  70                 unfakeable way. See
  71                 <citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>
  72                 for more information about the collected meta data.
  73                 </para>
  74
  75                 <para>Log data collected by the journal is primarily
  76                 text based but can also include binary data where
  77                 necessary. All objects stored in the journal can be up
  78                 to 2^64-1 bytes in size.</para>
  79
  80                 <para>By default the journal stores log data in
  81                 <filename>/run/log/journal/</filename>. Since
  82                 <filename>/run/</filename> is volatile log data is
  83                 lost at reboot. To make the data persistent it
  84                 is sufficient to create
  85                 <filename>/var/log/journal/</filename> where
  86                 <filename>systemd-journald</filename> will then store
  87                 the data.</para>
  88
  89                 <para><filename>systemd-journald</filename> will
  90                 forward all received log messages to the AF_UNIX
  91                 SOCK_DGRAM socket
  92                 <filename>/run/systemd/journal/syslog</filename> (if it exists) which
  93                 may be used by UNIX syslog daemons to process the data
  94                 further.</para>
  95
  96                 <para>See
  97                 <citerefentry><refentrytitle>journald.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>
  98                 for information about the configuration of this
  99                 service.</para>
 100         </refsect1>
 101
 102         <refsect1>
 103                 <title>Signals</title>
 104
 105                 <variablelist>
 106                         <varlistentry>
 107                                 <term>SIGUSR1</term>
 108
 109                                 <listitem><para>Request that journal
 110                                 data from <filename>/run/</filename>
 111                                 is flushed to
 112                                 <filename>/var/</filename> in order to
 113                                 make it persistent (if this is
 114                                 enabled). This may be used after
 115                                 <filename>/var/</filename> is mounted,
 116                                 but is generally not required since
 117                                 the first journal write when
 118                                 <filename>/var/</filename> becomes
 119                                 writable triggers the flushing
 120                                 anyway.</para></listitem>
 121                         </varlistentry>
 122
 123                         <varlistentry>
 124                                 <term>SIGUSR2</term>
 125
 126                                 <listitem><para>Request immediate
 127                                 rotation of the journal
 128                                 files.</para></listitem>
 129                         </varlistentry>
 130                 </variablelist>
 131         </refsect1>
 132
 133         <refsect1>
 134                 <title>Kernel Command Line</title>
 135
 136                 <para>A few configuration parameters from
 137                 <filename>journald.conf</filename> may be overriden on
 138                 the kernel command line:</para>
 139
 140                 <variablelist>
 141                         <varlistentry>
 142                                 <term><varname>systemd.journald.forward_to_syslog=</varname></term>
 143                                 <term><varname>systemd.journald.forward_to_kmsg=</varname></term>
 144                                 <term><varname>systemd.journald.forward_to_console=</varname></term>
 145
 146                                 <listitem><para>Enables/disables
 147                                 forwarding of collected log messages
 148                                 to syslog, the kernel log buffer or
 149                                 the system console.
 150                                 </para>
 151
 152                                 <para>See
 153                                 <citerefentry><refentrytitle>journald.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 154                                 for information about these settings.</para>
 155                                 </listitem>
 156
 157                         </varlistentry>
 158                 </variablelist>
 159         </refsect1>
 160
 161
 162         <refsect1>
 163                 <title>See Also</title>
 164                 <para>
 165                         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 166                         <citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 167                         <citerefentry><refentrytitle>journald.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 168                         <citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 169                 </para>
 170         </refsect1>
 171
 172 </refentry>