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39 lines
1.5 KiB
Markdown
39 lines
1.5 KiB
Markdown
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# Logging {#sec-logging}
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System-wide logging is provided by systemd's *journal*, which subsumes
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traditional logging daemons such as syslogd and klogd. Log entries are
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kept in binary files in `/var/log/journal/`. The command `journalctl`
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allows you to see the contents of the journal. For example,
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```ShellSession
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$ journalctl -b
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```
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shows all journal entries since the last reboot. (The output of
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`journalctl` is piped into `less` by default.) You can use various
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options and match operators to restrict output to messages of interest.
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For instance, to get all messages from PostgreSQL:
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```ShellSession
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$ journalctl -u postgresql.service
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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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```
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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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```ShellSession
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$ journalctl -b -p crit
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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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```
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The system journal is readable by root and by users in the `wheel` and
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`systemd-journal` groups. All users have a private journal that can be
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read using `journalctl`.
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