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</style><a href="index.html">Index </a>·
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<a href="systemd.directives.html">Directives </a>·
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<a href="../python-systemd/index.html">Python </a>·
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<a href="../libudev/index.html">libudev </a>·
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<a href="../libudev/index.html">gudev </a><span style="float:right">systemd 217</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-dev-log.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">systemd-journald-dev-log.socket</code></p><p><code class="filename">/usr/lib/systemd/systemd-journald</code></p></div><div class="refsect1"><a name="idm214180661472"></a><h2 id="Description">Description<a class="headerlink" title="Permalink to this headline" href="#Description">¶</a></h2><p><code class="filename">systemd-journald</code> is a
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system service that collects and stores logging data.
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It creates and maintains structured, indexed journals
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based on logging information that is received from the
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kernel, from user processes via the libc
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<a href="http://man7.org/linux/man-pages/man3/syslog.3.html"><span class="citerefentry"><span class="refentrytitle">syslog</span>(3)</span></a>
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call, from standard input and standard error of system
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services or via its native API. It will implicitly
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collect numerous metadata fields for each log
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messages in a secure and unfakeable way. See
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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 metadata.
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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 <code class="constant">AF_UNIX</code>
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<code class="constant">SOCK_DGRAM</code> socket
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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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further.</p><p>See
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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="idm214184603344"></a><h2 id="Signals">Signals<a class="headerlink" title="Permalink to this headline" href="#Signals">¶</a></h2><div class="variablelist"><dl class="variablelist"><dt id="SIGUSR1"><span class="term">SIGUSR1</span><a class="headerlink" title="Permalink to this term" href="#SIGUSR1">¶</a></dt><dd><p>Request that journal
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data from <code class="filename">/run/</code>
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is flushed to
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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 must be used after
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<code class="filename">/var/</code> is mounted,
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as otherwise log data from
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<code class="filename">/run</code> is never
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flushed to <code class="filename">/var</code>
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regardless of the
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configuration.</p></dd><dt id="SIGUSR2"><span class="term">SIGUSR2</span><a class="headerlink" title="Permalink to this term" href="#SIGUSR2">¶</a></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="idm214184595536"></a><h2 id="Kernel Command Line">Kernel Command Line<a class="headerlink" title="Permalink to this headline" href="#Kernel%20Command%20Line">¶</a></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 id="systemd.journald.forward_to_syslog="><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><span class="term"><code class="varname">systemd.journald.forward_to_wall=</code></span><a class="headerlink" title="Permalink to this term" href="#systemd.journald.forward_to_syslog=">¶</a></dt><dd><p>Enables/disables
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forwarding of collected log messages
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to syslog, the kernel log buffer, the
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system console or wall.
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</p><p>See
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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="idm214184588240"></a><h2 id="Access Control">Access Control<a class="headerlink" title="Permalink to this headline" href="#Access%20Control">¶</a></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 are 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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files created in the
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<code class="filename">/var/log/journal/</code>
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directory.</p></div><div class="refsect1"><a name="idm214184573264"></a><h2 id="Files">Files<a class="headerlink" title="Permalink to this headline" href="#Files">¶</a></h2><div class="variablelist"><dl class="variablelist"><dt id="/etc/systemd/journald.conf"><span class="term"><code class="filename">/etc/systemd/journald.conf</code></span><a class="headerlink" title="Permalink to this term" href="#/etc/systemd/journald.conf">¶</a></dt><dd><p>Configure
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<span class="command"><strong>systemd-journald</strong></span>
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behaviour. See
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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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</p></dd><dt id="/run/log/journal/machine-id/*.journal"><span class="term"><code class="filename">/run/log/journal/<em class="replaceable"><code>machine-id</code></em>/*.journal</code>, </span><span class="term"><code class="filename">/run/log/journal/<em class="replaceable"><code>machine-id</code></em>/*.journal~</code>, </span><span class="term"><code class="filename">/var/log/journal/<em class="replaceable"><code>machine-id</code></em>/*.journal</code>, </span><span class="term"><code class="filename">/var/log/journal/<em class="replaceable"><code>machine-id</code></em>/*.journal~</code></span><a class="headerlink" title="Permalink to this term" href="#/run/log/journal/machine-id/*.journal">¶</a></dt><dd><p><span class="command"><strong>systemd-journald</strong></span>
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writes entries to files in
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<code class="filename">/run/log/journal/<em class="replaceable"><code>machine-id</code></em>/</code>
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or
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<code class="filename">/var/log/journal/<em class="replaceable"><code>machine-id</code></em>/</code>
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with the "<code class="literal">.journal</code>"
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suffix. If the daemon is stopped
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uncleanly, or if the files are found
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to be corrupted, they are renamed
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using the "<code class="literal">.journal~</code>"
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suffix, and
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<span class="command"><strong>systemd-journald</strong></span>
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starts writing to a new
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file. <code class="filename">/run</code> is
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used when
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<code class="filename">/var/log/journal</code>
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is not available, or when
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<code class="option">Storage=volatile</code> is
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set in the
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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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configuration file.
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</p></dd></dl></div></div><div class="refsect1"><a name="idm214179589488"></a><h2 id="See Also">See Also<a class="headerlink" title="Permalink to this headline" href="#See%20Also">¶</a></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="systemd-coredump.html"><span class="citerefentry"><span class="refentrytitle">systemd-coredump</span>(8)</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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<span class="command"><strong>pydoc systemd.journal</strong></span>.
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</p></div></div></body></html>
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