jourtnalctl cheat sheet

journalctl man page.

Related: systemctl

Configuration

Is in /etc/systemd/journald.conf.

Environment Vars

$SYSTEMD_PAGER overwrites $PAGER. Setting this to “” or “cat” is equivalent to passing --no-pager.

Show…

Show service-name log

journalctl --no-pager -u _service-name_

Show events since the last boot

journalctl -b

Show today events

journalctl --since=today

Show (follow) current events

journalctl -f

Show the Last 50 error-level logs

journalctl -p err -n 50

Log Size Control

Retain only the past two days:

journalctl --vacuum-time=2d

Retain only the past 500 MB:

journalctl --vacuum-size=500M

Explain the messages

Jump to the end, explain the messages:

journalctl -xe

Explain the messages from the very beginning:

journalctl -x --no-pager