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-dev-log.socket
</refname>
49 <refname>systemd-journald-audit.socket
</refname>
50 <refname>systemd-journald
</refname>
51 <refpurpose>Journal service
</refpurpose>
55 <para><filename>systemd-journald.service
</filename></para>
56 <para><filename>systemd-journald.socket
</filename></para>
57 <para><filename>systemd-journald-dev-log.socket
</filename></para>
58 <para><filename>systemd-journald-audit.socket
</filename></para>
59 <para><filename>/usr/lib/systemd/systemd-journald
</filename></para>
63 <title>Description
</title>
65 <para><filename>systemd-journald
</filename> is a system service
66 that collects and stores logging data. It creates and maintains
67 structured, indexed journals based on logging information that is
68 received from a variety of sources:
</para>
71 <listitem><para>Kernel log messages, via kmsg
</para></listitem>
73 <listitem><para>Simple system log messages, via the libc
74 <citerefentry project='man-pages'
><refentrytitle>syslog
</refentrytitle><manvolnum>3</manvolnum></citerefentry>
75 call
</para></listitem>
77 <listitem><para>Structured system log messages via the native
79 <citerefentry><refentrytitle>sd_journal_print
</refentrytitle><manvolnum>4</manvolnum></citerefentry></para></listitem>
81 <listitem><para>Standard output and standard error of system
82 services
</para></listitem>
84 <listitem><para>Audit records, via the audit
85 subsystem
</para></listitem>
88 <para>The daemon will implicitly collect numerous metadata fields
89 for each log messages in a secure and unfakeable way. See
90 <citerefentry><refentrytitle>systemd.journal-fields
</refentrytitle><manvolnum>7</manvolnum></citerefentry>
91 for more information about the collected metadata.
94 <para>Log data collected by the journal is primarily text-based
95 but can also include binary data where necessary. All objects
96 stored in the journal can be up to
2^
64-
1 bytes in size.
</para>
98 <para>By default, the journal stores log data in
99 <filename>/run/log/journal/
</filename>. Since
100 <filename>/run/
</filename> is volatile, log data is lost at
101 reboot. To make the data persistent, it is sufficient to create
102 <filename>/var/log/journal/
</filename> where
103 <filename>systemd-journald
</filename> will then store the
106 <programlisting>mkdir -p /var/log/journal
107 systemd-tmpfiles --create --prefix /var/log/journal
</programlisting>
110 <citerefentry><refentrytitle>journald.conf
</refentrytitle><manvolnum>5</manvolnum></citerefentry>
111 for information about the configuration of this service.
</para>
115 <title>Signals
</title>
121 <listitem><para>Request that journal data from
122 <filename>/run/
</filename> is flushed to
123 <filename>/var/
</filename> in order to make it persistent (if
124 this is enabled). This must be used after
125 <filename>/var/
</filename> is mounted, as otherwise log data
126 from
<filename>/run
</filename> is never flushed to
127 <filename>/var
</filename> regardless of the configuration. The
128 <command>journalctl --flush
</command> command uses this signal
129 to request flushing of the journal files, and then waits for
130 the operation to complete. See
131 <citerefentry><refentrytitle>journalctl
</refentrytitle><manvolnum>1</manvolnum></citerefentry>
132 for details.
</para></listitem>
138 <listitem><para>Request immediate rotation of the journal
139 files. The
<command>journalctl --rotate
</command> command uses
140 this signal to request journal file
141 rotation.
</para></listitem>
145 <term>SIGRTMIN+
1</term>
147 <listitem><para>Request that all unwritten log data is written
148 to disk. The
<command>journalctl --sync
</command> command uses
149 this signal to trigger journal synchronization, and then waits
150 for the operation to complete.
</para></listitem>
156 <title>Kernel Command Line
</title>
158 <para>A few configuration parameters from
159 <filename>journald.conf
</filename> may be overridden on the kernel
162 <variablelist class='kernel-commandline-options'
>
164 <term><varname>systemd.journald.forward_to_syslog=
</varname></term>
165 <term><varname>systemd.journald.forward_to_kmsg=
</varname></term>
166 <term><varname>systemd.journald.forward_to_console=
</varname></term>
167 <term><varname>systemd.journald.forward_to_wall=
</varname></term>
169 <listitem><para>Enables/disables forwarding of collected log
170 messages to syslog, the kernel log buffer, the system console
175 <citerefentry><refentrytitle>journald.conf
</refentrytitle><manvolnum>5</manvolnum></citerefentry>
176 for information about these settings.
</para>
184 <title>Access Control
</title>
186 <para>Journal files are, by default, owned and readable by the
187 <literal>systemd-journal
</literal> system group but are not
188 writable. Adding a user to this group thus enables her/him to read
189 the journal files.
</para>
191 <para>By default, each logged in user will get her/his own set of
192 journal files in
<filename>/var/log/journal/
</filename>. These
193 files will not be owned by the user, however, in order to avoid
194 that the user can write to them directly. Instead, file system
195 ACLs are used to ensure the user gets read access only.
</para>
197 <para>Additional users and groups may be granted access to journal
198 files via file system access control lists (ACL). Distributions
199 and administrators may choose to grant read access to all members
200 of the
<literal>wheel
</literal> and
<literal>adm
</literal> system
201 groups with a command such as the following:
</para>
203 <programlisting># setfacl -Rnm g:wheel:rx,d:g:wheel:rx,g:adm:rx,d:g:adm:rx /var/log/journal/
</programlisting>
205 <para>Note that this command will update the ACLs both for
206 existing journal files and for future journal files created in the
207 <filename>/var/log/journal/
</filename> directory.
</para>
215 <term><filename>/etc/systemd/journald.conf
</filename></term>
217 <listitem><para>Configure
218 <command>systemd-journald
</command>
220 <citerefentry><refentrytitle>journald.conf
</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
225 <term><filename>/run/log/journal/
<replaceable>machine-id
</replaceable>/*.journal
</filename></term>
226 <term><filename>/run/log/journal/
<replaceable>machine-id
</replaceable>/*.journal~
</filename></term>
227 <term><filename>/var/log/journal/
<replaceable>machine-id
</replaceable>/*.journal
</filename></term>
228 <term><filename>/var/log/journal/
<replaceable>machine-id
</replaceable>/*.journal~
</filename></term>
230 <listitem><para><command>systemd-journald
</command> writes
232 <filename>/run/log/journal/
<replaceable>machine-id
</replaceable>/
</filename>
234 <filename>/var/log/journal/
<replaceable>machine-id
</replaceable>/
</filename>
235 with the
<literal>.journal
</literal> suffix. If the daemon is
236 stopped uncleanly, or if the files are found to be corrupted,
237 they are renamed using the
<literal>.journal~
</literal>
238 suffix, and
<command>systemd-journald
</command> starts writing
239 to a new file.
<filename>/run
</filename> is used when
240 <filename>/var/log/journal
</filename> is not available, or
241 when
<option>Storage=volatile
</option> is set in the
242 <citerefentry><refentrytitle>journald.conf
</refentrytitle><manvolnum>5</manvolnum></citerefentry>
243 configuration file.
</para></listitem>
247 <term><filename>/dev/kmsg
</filename></term>
248 <term><filename>/dev/log
</filename></term>
249 <term><filename>/run/systemd/journal/dev-log
</filename></term>
250 <term><filename>/run/systemd/journal/socket
</filename></term>
251 <term><filename>/run/systemd/journal/stdout
</filename></term>
253 <listitem><para>Sockets and other paths that
254 <command>systemd-journald
</command> will listen on that are
255 visible in the file system. In addition to these, journald can
256 listen for audit events using netlink.
</para></listitem>
262 <title>See Also
</title>
264 <citerefentry><refentrytitle>systemd
</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
265 <citerefentry><refentrytitle>journalctl
</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
266 <citerefentry><refentrytitle>journald.conf
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
267 <citerefentry><refentrytitle>systemd.journal-fields
</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
268 <citerefentry><refentrytitle>sd-journal
</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
269 <citerefentry><refentrytitle>systemd-coredump
</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
270 <citerefentry project='die-net'
><refentrytitle>setfacl
</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
271 <citerefentry><refentrytitle>sd_journal_print
</refentrytitle><manvolnum>4</manvolnum></citerefentry>,
272 <command>pydoc systemd.journal
</command>