<?xml version='1.0'?> <!--*-nxml-*-->
-<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
+<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
-
-<!--
- This file is part of systemd.
-
- Copyright 2010 Lennart Poettering
-
- systemd is free software; you can redistribute it and/or modify it
- under the terms of the GNU Lesser General Public License as published by
- the Free Software Foundation; either version 2.1 of the License, or
- (at your option) any later version.
-
- systemd is distributed in the hope that it will be useful, but
- WITHOUT ANY WARRANTY; without even the implied warranty of
- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
- Lesser General Public License for more details.
-
- You should have received a copy of the GNU Lesser General Public License
- along with systemd; If not, see <http://www.gnu.org/licenses/>.
--->
+<!-- SPDX-License-Identifier: LGPL-2.1+ -->
<refentry id="systemd-journald.service">
<refentryinfo>
<title>systemd-journald.service</title>
<productname>systemd</productname>
-
- <authorgroup>
- <author>
- <contrib>Developer</contrib>
- <firstname>Lennart</firstname>
- <surname>Poettering</surname>
- <email>lennart@poettering.net</email>
- </author>
- </authorgroup>
</refentryinfo>
<refmeta>
<refname>systemd-journald.socket</refname>
<refname>systemd-journald-dev-log.socket</refname>
<refname>systemd-journald-audit.socket</refname>
+ <refname>systemd-journald@.service</refname>
+ <refname>systemd-journald@.socket</refname>
+ <refname>systemd-journald-varlink@.socket</refname>
<refname>systemd-journald</refname>
<refpurpose>Journal service</refpurpose>
</refnamediv>
<para><filename>systemd-journald.socket</filename></para>
<para><filename>systemd-journald-dev-log.socket</filename></para>
<para><filename>systemd-journald-audit.socket</filename></para>
+ <para><filename>systemd-journald@.service</filename></para>
+ <para><filename>systemd-journald@.socket</filename></para>
+ <para><filename>systemd-journald-varlink@.socket</filename></para>
<para><filename>/usr/lib/systemd/systemd-journald</filename></para>
</refsynopsisdiv>
<listitem><para>Structured system log messages via the native
Journal API, see
- <citerefentry><refentrytitle>sd_journal_print</refentrytitle><manvolnum>4</manvolnum></citerefentry></para></listitem>
+ <citerefentry><refentrytitle>sd_journal_print</refentrytitle><manvolnum>3</manvolnum></citerefentry></para></listitem>
<listitem><para>Standard output and standard error of service units. For further details see
below.</para></listitem>
for more information about the collected metadata.
</para>
- <para>Log data collected by the journal is primarily text-based
- but can also include binary data where necessary. All objects
- stored in the journal can be up to 2^64-1 bytes in size.</para>
+ <para>Log data collected by the journal is primarily text-based but can also include binary data where
+ necessary. Individual fields making up a log record stored in the journal may be up to 2^64-1 bytes in size.</para>
+
+ <para>The journal service stores log data either persistently below <filename>/var/log/journal</filename> or in a
+ volatile way below <filename>/run/log/journal/</filename> (in the latter case it is lost at reboot). By default, log
+ data is stored persistently if <filename>/var/log/journal/</filename> exists during boot, with an implicit fallback
+ to volatile storage otherwise. Use <varname>Storage=</varname> in
+ <citerefentry><refentrytitle>journald.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry> to configure
+ where log data is placed, independently of the existence of <filename>/var/log/journal/</filename>.</para>
- <para>By default, the journal stores log data in
- <filename>/run/log/journal/</filename>. Since
- <filename>/run/</filename> is volatile, log data is lost at
- reboot. To make the data persistent, it is sufficient to create
- <filename>/var/log/journal/</filename> where
- <filename>systemd-journald</filename> will then store the
- data:</para>
+ <para>On systems where <filename>/var/log/journal/</filename> does not exist yet but where persistent logging is
+ desired (and the default <filename>journald.conf</filename> is used), it is sufficient to create the directory, and
+ ensure it has the correct access modes and ownership:</para>
<programlisting>mkdir -p /var/log/journal
systemd-tmpfiles --create --prefix /var/log/journal</programlisting>
<para>If <filename>systemd-journald.service</filename> is stopped, the stream connections associated with all
services are terminated. Further writes to those streams by the service will result in <constant>EPIPE</constant>
errors. In order to react gracefully in this case it is recommended that programs logging to standard output/error
- ignore such errors. If the the <constant>SIGPIPE</constant> UNIX signal handler is not blocked or turned off, such
+ ignore such errors. If the <constant>SIGPIPE</constant> UNIX signal handler is not blocked or turned off, such
write attempts will also result in such process signals being generated, see
- <citerefentry><refentrytitle>signal</refentrytitle><manvolnum>7</manvolnum></citerefentry>. To mitigate this issue,
- systemd service manager explicitly turns off the <constant>SIGPIPE</constant> signal for all invoked processes by
- default (this may be changed for each unit individually via the <varname>IgnoreSIGPIPE=</varname> option, see
+ <citerefentry project='man-pages'><refentrytitle>signal</refentrytitle><manvolnum>7</manvolnum></citerefentry>.
+ To mitigate this issue, systemd service manager explicitly turns off the <constant>SIGPIPE</constant>
+ signal for all invoked processes by default (this may be changed for each unit individually via the
+ <varname>IgnoreSIGPIPE=</varname> option, see
<citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry> for
- details). After the standard output/standard error streams have been terminated they may not be recovered until the
- services they are associated with are restarted. Note that during normal operation,
- <filename>systemd-journald.service</filename> stores copies of the file descriptors for those streams in the
- service manager. If <filename>systemd-journald.service</filename> is restarted using <command>systemctl
- restart</command> or equivalent operation instead of a pair of separate <command>systemctl stop</command> and
- <command>systemctl start</command> commands (or equivalent operations), these stream connections are not terminated
- and survive the restart. It is thus safe to restart <filename>systemd-journald.service</filename>, but stopping it
- is not recommended.</para>
+ details). After the standard output/standard error streams have been terminated they may not be recovered
+ until the services they are associated with are restarted. Note that during normal operation,
+ <filename>systemd-journald.service</filename> stores copies of the file descriptors for those streams in
+ the service manager. If <filename>systemd-journald.service</filename> is restarted using
+ <command>systemctl restart</command> or equivalent operation instead of a pair of separate
+ <command>systemctl stop</command> and <command>systemctl start</command> commands (or equivalent
+ operations), these stream connections are not terminated and survive the restart. It is thus safe to
+ restart <filename>systemd-journald.service</filename>, but stopping it is not recommended.</para>
<para>Note that the log record metadata for records transferred via such standard output/error streams reflect the
metadata of the peer the stream was originally created for. If the stream connection is passed on to other
transports listed above, which are inherently record based and where the metadata is always associated with the
individual record.</para>
- <para>In addition to the the implicit standard output/error logging of services, stream logging is also available
+ <para>In addition to the implicit standard output/error logging of services, stream logging is also available
via the <citerefentry><refentrytitle>systemd-cat</refentrytitle><manvolnum>1</manvolnum></citerefentry> command
line tool.</para>
<para>Currently, the number of parallel log streams <filename>systemd-journald</filename> will accept is limited to
- 4096. When this limit is reached further log streams may be established but will receieve
+ 4096. When this limit is reached further log streams may be established but will receive
<constant>EPIPE</constant> right from the beginning.</para>
</refsect1>
+ <refsect1>
+ <title>Journal Namespaces</title>
+
+ <para>Journal 'namespaces' are both a mechanism for logically isolating the log stream of projects
+ consisting of one or more services from the rest of the system and a mechanism for improving
+ performance. Multiple journal namespaces may exist simultaneously, each defining its own, independent log
+ stream managed by its own instance of <command>systemd-journald</command>. Namespaces are independent of
+ each other, both in the data store and in the IPC interface. By default only a single 'default' namespace
+ exists, managed by <filename>systemd-journald.service</filename> (and its associated socket
+ units). Additional namespaces are created by starting an instance of the
+ <filename>systemd-journald@.service</filename> service template. The instance name is the namespace
+ identifier, which is a short string used for referencing the journal namespace. Service units may be
+ assigned to a specific journal namespace through the <varname>LogNamespace=</varname> unit file setting,
+ see <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry> for
+ details. The <option>--namespace=</option> switch of
+ <citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>1</manvolnum></citerefentry> may be
+ used to view the log stream of a specific namespace. If the switch is not used the log stream of the
+ default namespace is shown, i.e. log data from other namespaces is not visible.</para>
+
+ <para>Services associated with a specific log namespace may log via syslog, the native logging protocol
+ of the journal and via stdout/stderr; the logging from all three transports is associated with the
+ namespace.</para>
+
+ <para>By default only the default namespace will collect kernel and audit log messages.</para>
+
+ <para>The <command>systemd-journald</command> instance of the default namespace is configured through
+ <filename>/etc/systemd/journald.conf</filename> (see below), while the other instances are configured
+ through <filename>/etc/systemd/journald@<replaceable>NAMESPACE</replaceable>.conf</filename>. The journal
+ log data for the default namespace is placed in
+ <filename>/var/log/journal/<replaceable>MACHINE_ID</replaceable></filename> (see below) while the data
+ for the other namespaces is located in
+ <filename>/var/log/journal/<replaceable>MACHINE_ID</replaceable>.<replaceable>NAMESPACE</replaceable></filename>.</para>
+ </refsect1>
+
<refsect1>
<title>Signals</title>
<varlistentry>
<term>SIGUSR1</term>
- <listitem><para>Request that journal data from
- <filename>/run/</filename> is flushed to
- <filename>/var/</filename> in order to make it persistent (if
- this is enabled). This must be used after
- <filename>/var/</filename> is mounted, as otherwise log data
- from <filename>/run</filename> is never flushed to
- <filename>/var</filename> regardless of the configuration. The
- <command>journalctl --flush</command> command uses this signal
- to request flushing of the journal files, and then waits for
+ <listitem><para>Request that journal data from <filename>/run/</filename> is flushed to
+ <filename>/var/</filename> in order to make it persistent (if this is enabled). This must be used
+ after <filename>/var/</filename> is mounted, as otherwise log data from <filename>/run</filename> is
+ never flushed to <filename>/var</filename> regardless of the configuration. Use the
+ <command>journalctl --flush</command> command to request flushing of the journal files, and wait for
the operation to complete. See
- <citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
- for details.</para></listitem>
+ <citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>1</manvolnum></citerefentry> for
+ details.</para></listitem>
</varlistentry>
<varlistentry>
<term>SIGUSR2</term>
- <listitem><para>Request immediate rotation of the journal
- files. The <command>journalctl --rotate</command> command uses
- this signal to request journal file
- rotation.</para></listitem>
+ <listitem><para>Request immediate rotation of the journal files. Use the <command>journalctl
+ --rotate</command> command to request journal file rotation, and wait for the operation to
+ complete.</para></listitem>
</varlistentry>
<varlistentry>
<term>SIGRTMIN+1</term>
- <listitem><para>Request that all unwritten log data is written
- to disk. The <command>journalctl --sync</command> command uses
- this signal to trigger journal synchronization, and then waits
- for the operation to complete.</para></listitem>
+ <listitem><para>Request that all unwritten log data is written to disk. Use the <command>journalctl
+ --sync</command> command to trigger journal synchronization, and wait for the operation to
+ complete.</para></listitem>
</varlistentry>
</variablelist>
</refsect1>
</varlistentry>
</variablelist>
+
+ <para>Note that these kernel command line options are only honoured by the default namespace, see
+ above.</para>
</refsect1>
<refsect1>
<para>Journal files are, by default, owned and readable by the
<literal>systemd-journal</literal> system group but are not
- writable. Adding a user to this group thus enables her/him to read
+ writable. Adding a user to this group thus enables them to read
the journal files.</para>
- <para>By default, each logged in user will get her/his own set of
- journal files in <filename>/var/log/journal/</filename>. These
+ <para>By default, each user, with a UID outside the range of system users,
+ dynamic service users, and the nobody user, will get their own set of
+ journal files in <filename>/var/log/journal/</filename>. See
+ <ulink url="https://systemd.io/UIDS-GIDS">Users, Groups, UIDs and GIDs on systemd systems</ulink>
+ for more details about UID ranges. These journal
files will not be owned by the user, however, in order to avoid
that the user can write to them directly. Instead, file system
ACLs are used to ensure the user gets read access only.</para>
<varlistentry>
<term><filename>/etc/systemd/journald.conf</filename></term>
- <listitem><para>Configure
- <command>systemd-journald</command>
- behavior. See
+ <listitem><para>Configure <command>systemd-journald</command> behavior. See
<citerefentry><refentrytitle>journald.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
</para></listitem>
</varlistentry>
<term><filename>/var/log/journal/<replaceable>machine-id</replaceable>/*.journal</filename></term>
<term><filename>/var/log/journal/<replaceable>machine-id</replaceable>/*.journal~</filename></term>
- <listitem><para><command>systemd-journald</command> writes
- entries to files in
+ <listitem><para><command>systemd-journald</command> writes entries to files in
<filename>/run/log/journal/<replaceable>machine-id</replaceable>/</filename>
or
<filename>/var/log/journal/<replaceable>machine-id</replaceable>/</filename>
<filename>/var/log/journal</filename> is not available, or
when <option>Storage=volatile</option> is set in the
<citerefentry><refentrytitle>journald.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>
- configuration file.</para></listitem>
+ configuration file.</para>
+
+ <para>When <filename>systemd-journald</filename> ceases writing to a journal file,
+ it will be renamed to <literal><replaceable>original-name</replaceable>@<replaceable>suffix.journal</replaceable></literal>
+ (or <literal><replaceable>original-name</replaceable>@<replaceable>suffix.journal~</replaceable></literal>).
+ Such files are "archived" and will not be written to any more.</para>
+
+ <para>In general, it is safe to read or copy any journal file (active or archived).
+ <citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
+ and the functions in the
+ <citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+ library should be able to read all entries that have been fully written.</para>
+
+ <para><filename>systemd-journald</filename> will automatically remove the oldest
+ archived journal files to limit disk use. See <varname>SystemMaxUse=</varname>
+ and related settings in
+ <citerefentry><refentrytitle>journald.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
+ </para></listitem>
</varlistentry>
<varlistentry>
<term><filename>/run/systemd/journal/socket</filename></term>
<term><filename>/run/systemd/journal/stdout</filename></term>
- <listitem><para>Sockets and other paths that
- <command>systemd-journald</command> will listen on that are
- visible in the file system. In addition to these, journald can
- listen for audit events using netlink.</para></listitem>
+ <listitem><para>Sockets and other file node paths that <command>systemd-journald</command> will
+ listen on and are visible in the file system. In addition to these,
+ <command>systemd-journald</command> can listen for audit events using <citerefentry
+ project='man-pages'><refentrytitle>netlink</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para></listitem>
</varlistentry>
</variablelist>
+
+ <para>If journal namespacing is used these paths are slightly altered to include a namespace identifier, see above.</para>
</refsect1>
<refsect1>
<citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd-coredump</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
- <citerefentry project='die-net'><refentrytitle>setfacl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>sd_journal_print</refentrytitle><manvolnum>4</manvolnum></citerefentry>,
+ <citerefentry project='man-pages'><refentrytitle>setfacl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_journal_print</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<command>pydoc systemd.journal</command>
</para>
</refsect1>
projects / thirdparty / systemd.git / blobdiff