Today I learned about journalctl. This tool is used to investigate logs from systems based on systemd. With this command, it is much easier to investigate various logs. It is the main interface to query journals that are stored in binary format and already indexed.
journalctl [OPTIONS] [FILTERS]
You can filter by service:
journalctl -u nginx # specific service
journalctl -u nginx -u php-fpm # multiple services
journalctl -u docker -f # follow specific service
Or see disk usage and manipulate it
journalctl --disk-usage # check current usage
journalctl --vacuum-size=500M # reduce to 500MB
journalctl --vacuum-time=2weeks # keep only last 2 weeks
To set a permanent limit, edit /etc/systemd/journald.conf:
[Journal]
SystemMaxUse=500M
for help see:
journalctl --help