Cleanup systemd /var/log/journal/

You can control the size of this directory by editing /etc/systemd/journald.conf:

SystemMaxUse=500M

Query journalctl to find out how much disk space it's consuming:

journalctl --disk-usage

Delete old log files:

journalctl --vacuum-size=500M

You can also clean based on time:

journalctl --vacuum-time=14d