2014-08-24 17:18:18 +00:00
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<chapter xmlns="http://docbook.org/ns/docbook"
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xmlns:xlink="http://www.w3.org/1999/xlink"
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xmlns:xi="http://www.w3.org/2001/XInclude"
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version="5.0"
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xml:id="sec-logging">
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2018-05-01 23:57:09 +00:00
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<title>Logging</title>
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<para>
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System-wide logging is provided by systemd’s <emphasis>journal</emphasis>,
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which subsumes traditional logging daemons such as syslogd and klogd. Log
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entries are kept in binary files in <filename>/var/log/journal/</filename>.
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The command <literal>journalctl</literal> allows you to see the contents of
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the journal. For example,
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2014-08-24 17:18:18 +00:00
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<screen>
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2019-06-17 11:25:50 +00:00
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<prompt>$ </prompt>journalctl -b
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2014-08-24 17:18:18 +00:00
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</screen>
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2018-05-01 23:57:09 +00:00
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shows all journal entries since the last reboot. (The output of
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<command>journalctl</command> is piped into <command>less</command> by
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default.) You can use various options and match operators to restrict output
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to messages of interest. For instance, to get all messages from PostgreSQL:
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2014-08-24 17:18:18 +00:00
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<screen>
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2019-06-17 11:25:50 +00:00
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<prompt>$ </prompt>journalctl -u postgresql.service
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2014-08-24 17:18:18 +00:00
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-- Logs begin at Mon, 2013-01-07 13:28:01 CET, end at Tue, 2013-01-08 01:09:57 CET. --
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...
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Jan 07 15:44:14 hagbard postgres[2681]: [2-1] LOG: database system is shut down
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-- Reboot --
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Jan 07 15:45:10 hagbard postgres[2532]: [1-1] LOG: database system was shut down at 2013-01-07 15:44:14 CET
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Jan 07 15:45:13 hagbard postgres[2500]: [1-1] LOG: database system is ready to accept connections
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</screen>
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2018-05-01 23:57:09 +00:00
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Or to get all messages since the last reboot that have at least a
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“critical” severity level:
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2014-08-24 17:18:18 +00:00
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<screen>
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2019-06-17 11:25:50 +00:00
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<prompt>$ </prompt>journalctl -b -p crit
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2014-08-24 17:18:18 +00:00
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Dec 17 21:08:06 mandark sudo[3673]: pam_unix(sudo:auth): auth could not identify password for [alice]
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Dec 29 01:30:22 mandark kernel[6131]: [1053513.909444] CPU6: Core temperature above threshold, cpu clock throttled (total events = 1)
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</screen>
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2018-05-01 23:57:09 +00:00
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</para>
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<para>
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The system journal is readable by root and by users in the
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<literal>wheel</literal> and <literal>systemd-journal</literal> groups. All
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users have a private journal that can be read using
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<command>journalctl</command>.
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</para>
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</chapter>
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