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<a href="../libudev/index.html">gudev </a><span style="float:right">systemd 202</span><hr><div class="refentry"><a name="systemd-journald.service"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>systemd-journald.service, systemd-journald.socket, systemd-journald — Journal service</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><p><code class="filename">systemd-journald.service</code></p><p><code class="filename">systemd-journald.socket</code></p><p><code class="filename">/usr/lib/systemd/systemd-journald</code></p></div><div class="refsect1"><a name="idp2969984"></a><h2>Description</h2><p><code class="filename">systemd-journald</code> is a
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system service that collects and stores logging
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data. It creates and maintains structured, indexed
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journals based on logging information that is received
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from the kernel, from user processes via the libc
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<a href="syslog.html"><span class="citerefentry"><span class="refentrytitle">syslog</span>(3)</span></a>
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call, from STDOUT/STDERR of system services or via its
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native API. It will implicitly collect numerous meta
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data fields for each log messages in a secure and
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<a href="systemd.journal-fields.html"><span class="citerefentry"><span class="refentrytitle">systemd.journal-fields</span>(7)</span></a>
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for more information about the collected meta data.
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</p><p>Log data collected by the journal is primarily
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text based but can also include binary data where
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necessary. All objects stored in the journal can be up
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to 2^64-1 bytes in size.</p><p>By default the journal stores log data in
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<code class="filename">/run/log/journal/</code>. Since
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<code class="filename">/run/</code> is volatile log data is
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lost at reboot. To make the data persistent it
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is sufficient to create
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<code class="filename">/var/log/journal/</code> where
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<code class="filename">systemd-journald</code> will then store
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the data.</p><p><code class="filename">systemd-journald</code> will
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forward all received log messages to the AF_UNIX
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<code class="filename">/run/systemd/journal/syslog</code> (if it exists) which
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may be used by UNIX syslog daemons to process the data
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<a href="journald.conf.html"><span class="citerefentry"><span class="refentrytitle">journald.conf</span>(5)</span></a>
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for information about the configuration of this
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service.</p></div><div class="refsect1"><a name="idp4809744"></a><h2>Signals</h2><div class="variablelist"><dl class="variablelist"><dt><span class="term">SIGUSR1</span></dt><dd><p>Request that journal
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data from <code class="filename">/run/</code>
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<code class="filename">/var/</code> in order to
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make it persistent (if this is
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enabled). This may be used after
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<code class="filename">/var/</code> is mounted,
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but is generally not required since
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the first journal write when
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<code class="filename">/var/</code> becomes
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writable triggers the flushing
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anyway.</p></dd><dt><span class="term">SIGUSR2</span></dt><dd><p>Request immediate
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rotation of the journal
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files.</p></dd></dl></div></div><div class="refsect1"><a name="idp3248992"></a><h2>Kernel Command Line</h2><p>A few configuration parameters from
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<code class="filename">journald.conf</code> may be overridden on
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the kernel command line:</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="varname">systemd.journald.forward_to_syslog=</code>, </span><span class="term"><code class="varname">systemd.journald.forward_to_kmsg=</code>, </span><span class="term"><code class="varname">systemd.journald.forward_to_console=</code></span></dt><dd><p>Enables/disables
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forwarding of collected log messages
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to syslog, the kernel log buffer or
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<a href="journald.conf.html"><span class="citerefentry"><span class="refentrytitle">journald.conf</span>(5)</span></a>
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for information about these settings.</p></dd></dl></div></div><div class="refsect1"><a name="idp2460864"></a><h2>Access Control</h2><p>Journal files are by default owned and readable
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by the <code class="literal">systemd-journal</code> system group
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(but not writable). Adding a user to this group thus
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enables her/him to read the journal files.</p><p>By default, each logged in user will get her/his
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own set of journal files in
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<code class="filename">/var/log/journal/</code>. These files
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will not be owned by the user however, in order to
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avoid that the user can write to them
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directly. Instead, file system ACLs are used to ensure
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the user gets read access only.</p><p>Additional users and groups may be granted
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access to journal files via file system access control
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lists (ACL). Distributions and administrators may
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choose to grant read access to all members of the
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<code class="literal">wheel</code> and <code class="literal">adm</code>
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system groups with a command such as the
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following:</p><pre class="programlisting"># setfacl -Rnm g:wheel:rx,d:g:wheel:rx,g:adm:rx,d:g:adm:rx /var/log/journal/</pre><p>Note that this command will update the ACLs both
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for existing journal files and for future journal
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<code class="filename">/var/log/journal/</code>
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directory.</p></div><div class="refsect1"><a name="idp2340640"></a><h2>See Also</h2><p>
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<a href="systemd.html"><span class="citerefentry"><span class="refentrytitle">systemd</span>(1)</span></a>,
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<a href="journalctl.html"><span class="citerefentry"><span class="refentrytitle">journalctl</span>(1)</span></a>,
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<a href="journald.conf.html"><span class="citerefentry"><span class="refentrytitle">journald.conf</span>(5)</span></a>,
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<a href="systemd.journal-fields.html"><span class="citerefentry"><span class="refentrytitle">systemd.journal-fields</span>(7)</span></a>,
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<a href="sd-journal.html"><span class="citerefentry"><span class="refentrytitle">sd-journal</span>(3)</span></a>,
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<a href="setfacl.html"><span class="citerefentry"><span class="refentrytitle">setfacl</span>(1)</span></a>
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</p></div></div></body></html>
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