What to do when journal is taking up a lot of space in your /var/log/ directory?

You can limit the disk space that is used by journald (the logging system) by modifying the following file:

/etc/systemd/journald.conf

Look for the line

#SystemMaxUse=

Uncomment it and set the max limit to e.g. 100M

SystemMaxUse=100M

This will cap the max disk usage for journald at 100MB.

Afer modifying the file you have to restart the journald service by running:

sudo service systemd-journald restart