/var/log/journal taking up lots of space
If /var/log/journal is taking up too much space, you can clear it and prevent it growing too big again.
Prevention:
vi /etc/systemd/journald.conf
Look for:
SystemMaxUse=2000M
Or similar, and set it to a lower value
Then:
service systemd-journald restart
Clearing once-off:
journalctl --vacuum-time=2d
assuming for example you want to clear everything before two days ago.