Cleanup
Check current disk usage:
sudo journalctl --disk-usage
Use rotate function:
sudo journalctl --rotate
Or
Remove all logs and keep the last 2 days:
sudo journalctl --vacuum-time=2days
Or
Remove all logs and only keep the last 100MB:
sudo journalctl --vacuum-size=100M
How to read logs:
Follow specific log for a service:
sudo journalctl -fu SERVICE
Show extended log info and print the last lines of a service:
sudo journalctl -xeu SERVICE