Journalctl Tricks

journalctl --disk-usage
journalctl --vacuum-size=1G

--vacuum-size=BYTES   Reduce disk usage below specified size
--vacuum-files=INT    Leave only the specified number of journal files
--vacuum-time=TIME    Remove journal files older than specified time

journcalctl --file /var/log/.../dsdsdsdsdsdsdsds.journal~

sudo journalctl -e

journalctl -e -u certbot.service
journalctl -xeu redis-server.service

journalctl --list-boots

journalctl -p err -b

journalctl -k -e

systemctl list-unit-files

systemctl --failed
# or
systemctl list-units --state=failed

journalctl -xb