How to use journalctl to view systemd logs?
One of the impetuses behind the systemd journal is to centralize the management of logs regardless of where the messages are originating. Since much of the boot process and service management is handled by the systemd process, it makes sense to standardize the way that logs are collected and accessed. The journald daemon collects data from all available sources and stores them in a binary format for easy and dynamic manipulation.
View logs by unit
journalctl -u nginx.service
Filter logs by time/date
journalctl -u nginx.service --since today
journalctl -u nginx.service --until "2012-10-30 18:17:16"
To actively follow the logs as they are being written, you can use the
-f flag. Again, this works as you might expect if you have experience using
To see the latest logs first
journalctl -r -u nginx.service
Find disk used by logs
This will remove old entries until the total journal space taken up on disk is at the requested size:
Keep the entries that have been created after a specific time: