옵션편집
-t --identifier=STRING Show entries with the specified syslog identifier
$ journalctl --identifier=cron
-f --follow Follow the journal
-o --output=STRING Change journal output mode (short, short-precise, short-iso, short-full, short-monotonic, short-unix, verbose, export, json, json-pretty, json-sse, cat)
$ journalctl -o verbose -t quotaon
-a --all Show all fields, including long and unprintable
-x --catalog Add message explanations where available
-S --since=DATE Show entries not older than the specified date
$ journalctl --since=today