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">
6 This file is part of systemd.
8 Copyright 2010 Lennart Poettering
10 systemd is free software; you can redistribute it and/or modify it
11 under the terms of the GNU Lesser General Public License as published by
12 the Free Software Foundation; either version 2.1 of the License, or
13 (at your option) any later version.
15 systemd is distributed in the hope that it will be useful, but
16 WITHOUT ANY WARRANTY; without even the implied warranty of
17 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
18 Lesser General Public License for more details.
20 You should have received a copy of the GNU Lesser General Public License
21 along with systemd; If not, see <http://www.gnu.org/licenses/>.
24 <refentry id="systemd-journald.service">
27 <title>systemd-journald.service</title>
28 <productname>systemd</productname>
32 <contrib>Developer</contrib>
33 <firstname>Lennart</firstname>
34 <surname>Poettering</surname>
35 <email>lennart@poettering.net</email>
41 <refentrytitle>systemd-journald.service</refentrytitle>
42 <manvolnum>8</manvolnum>
46 <refname>systemd-journald.service</refname>
47 <refname>systemd-journald.socket</refname>
48 <refname>systemd-journald</refname>
49 <refpurpose>Journal service</refpurpose>
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>
59 <title>Description</title>
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
71 <citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>
72 for more information about the collected meta data.
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>
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
89 <para><filename>systemd-journald</filename> will
90 forward all received log messages to the AF_UNIX
92 <filename>/run/systemd/journal/syslog</filename> (if it exists) which
93 may be used by UNIX syslog daemons to process the data
97 <citerefentry><refentrytitle>journald.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>
98 for information about the configuration of this
103 <title>Signals</title>
109 <listitem><para>Request that journal
110 data from <filename>/run/</filename>
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>
126 <listitem><para>Request immediate
127 rotation of the journal
128 files.</para></listitem>
134 <title>Kernel Command Line</title>
136 <para>A few configuration parameters from
137 <filename>journald.conf</filename> may be overridden on
138 the kernel command line:</para>
140 <variablelist class='kernel-commandline-options'>
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>
146 <listitem><para>Enables/disables
147 forwarding of collected log messages
148 to syslog, the kernel log buffer or
153 <citerefentry><refentrytitle>journald.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>
154 for information about these settings.</para>
162 <title>Access Control</title>
164 <para>Journal files are by default owned and readable
165 by the <literal>systemd-journal</literal> system group
166 (but not writable). Adding a user to this group thus
167 enables her/him to read the journal files.</para>
169 <para>By default, each logged in user will get her/his
170 own set of journal files in
171 <filename>/var/log/journal/</filename>. These files
172 will not be owned by the user however, in order to
173 avoid that the user can write to them
174 directly. Instead, file system ACLs are used to ensure
175 the user gets read access only.</para>
177 <para>Additional users and groups may be granted
178 access to journal files via file system access control
179 lists (ACL). Distributions and administrators may
180 choose to grant read access to all members of the
181 <literal>wheel</literal> and <literal>adm</literal>
182 system groups with a command such as the
185 <programlisting># setfacl -Rnm g:wheel:rx,d:g:wheel:rx,g:adm:rx,d:g:adm:rx /var/log/journal/</programlisting>
187 <para>Note that this command will update the ACLs both
188 for existing journal files and for future journal
190 <filename>/var/log/journal/</filename>
195 <title>See Also</title>
197 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
198 <citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
199 <citerefentry><refentrytitle>journald.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
200 <citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
201 <citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
202 <citerefentry><refentrytitle>setfacl</refentrytitle><manvolnum>1</manvolnum></citerefentry>