If you find yourself low on disk space, check the size of the Systemd journal logs as a way to easily free up some space.
$ sudo journalctl --disk-usage Archived and active journals take up 528.0M in the file system. # reduce size to 300 Mb sudo journalctl --vacuum-size=300M
There are automatic jobs that trim these Systemd journal logs, but invoking manually will force the operation.
Change journal disk utilization
If you want to permanently change amount of disk these logs can utilize, modify “/etc/systemd/journald.conf“. Setting the ‘SystemMaxUse’ key will keep the persistence below the threshold.
SystemMaxUse=300M
Restart the Systemd journal service or reboot for the change to take affect.
sudo systemctl restart systemd-journald
REFERENCES
stackexchange, how to clear journalctl
linuxhandbook.com, how to clear systemd journal logs
gist bearlike, clearing systemd journal logs on Ubuntu
NOTES
Another way to check disk utilization of journal logs
sudo du -m /var/log/journal | sort -n