Clear systemd journal

If the journal is configured to archive entires these can take up unnecessary disk space when not properly maintained. The current disk usage can be seen with journalctl --disk-usage. This includes both active and archived journal files.

Clear journal entries older then X number of days

$ journalctl --vacuum-time=5d

Clear journals exceeding X storage

$ journalctl --vacuum-size=2G

Flush journal to disk

Vacuuming only impacts journals that have been written to disk. It may be necessary to first flush in-memory journal entires to disk before a vacuum reduces disk usage.

$ journalctl --rotate