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