systemd: cleaning the space used by logs (journal)
systemd has its own logging system, that is managed by journalctl.
The idea is straightforward: instead of doing textual logging,
systemd uses its own format for logging and journalctl is the way to access, read and manage the logs.
Usually the logs are stored under
/var/log/journal, and this can grow to a very large amount of space.
journalctl provides special commands to clean up old logs: the commands are named vacuum and can be any combination of
vacuum-sizeindicates the max amount of data to keep in the logs;vacuum-timeindicates the max window of time to keep in the logs (i.e., logs within the last two days);vacuum-filesindicates how many file of logs to keep.
As an example, in the following I asks the system to rotate immediatly active logs (that cannot be vacuumed while active) and on inactive logs to reduce the size to
10 MB:
% sudo journalctl --rotate --vacuum-size=10M
Vacuuming done, freed 0B of archived journals from /run/log/journal.
Vacuuming done, freed 0B of archived journals from /var/log/journal.
Deleted archived journal /var/log/journal/6d428e8be03e4038b0c1aaabdb440f0f/user-1001@883a7dd1d8c9412fb6e3fc60f8dde880-00000000001d2294-0005bdf47397f855.journal (32.0M).
Deleted archived journal /var/log/journal/6d428e8be03e4038b0c1aaabdb440f0f/system@f57c826bb8fe473b8a350e05b81944d4-00000000001eef78-0005bdfc90bffe8c.journal (96.0M).
Deleted archived journal /var/log/journal/6d428e8be03e4038b0c1aaabdb440f0f/user-1000@3640d3cc286942239ebca805b28ae167-00000000001eef97-0005bdfc90dfde70.journal (32.0M).
...
At the end, the log directory will result in pretty much the specified size, with the exception of active and ongoing log activity.