So, you want to delete old log files in your Fedora system?

In my system the log space was getting big (more than 4Gb). Since nowadays we have these small solid state disks this can be a problem.

I checked Can I remove files in /var/log/journal and /var/cache/abrt-di/usr? and this instruction does the magic:

sudo journalctl --vacuum-size=500M

Moreover, you can activate log rotation with:

sudo systemctl kill --kill-who=main --signal=SIGUSR2 systemd-journald.service

and you'll need to restart the service:

sudo systemctl restart systemd-journald.service

Finally, if you want to check the size of your journaling logging space:

journalctl --disk-usage

Or, in the old-fashioned (and more 'physical') way:

du -h /var/log/journal/

No more complaints about the size of the root filesystem, for now.