# Logging

System-wide logging is provided by systemd’s journal, which subsumes traditional logging daemons such as syslogd and klogd. Log entries are kept in binary files in `/var/log/journal/`. The command `journalctl` allows you to see the contents of the journal. For example,

    $ journalctl -b

shows all journal entries since the last reboot. (The output of `journalctl` is piped into `less` 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:

    $ 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

Or to get all messages since the last reboot that have at least a critical severity level:

    $ 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)

The system journal is readable by root and by users in the `wheel` and `systemd-journal` groups. All users have a private journal that can be read using `journalctl`.