Configure journalctl

Check how much disk space is allocated for journalctl

sudo journalctl --disk-usage

Adjust journalctl diskspace allocation

In file /etc/systemd/journald.conf locate and adjust line SystemMaxUse=50M. Allocation of 50M is an example. By default this parameter might be commented in configuration file.

Restart journal to apply new settings and clean up history

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