I’d be interested to know how much your 15G server costs, and from which supplier. My 25G machine costs me $6 per month from Digital Ocean, and my 20G machine costs $3 from Hetzner.
If you don’t expect to have to debug any behaviour from system logs, you can be very brutal in pruning the journals.
# journalctl --rotate
# journalctl --vacuum-time=1s
although what I’ve done is change the policy:
/etc/systemd/journald.conf:
[Journal]
SystemMaxUse=50M
The disk usage on the 20G machine, which has a very small low-activity forum on it, is like this:
# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/sda1 19G 9.9G 8.1G 56% /
operating system:
15M /bin
16M /sbin
43M /boot/
135M /var/cache/
223M /var/log
435M /lib
464M /var/lib/apt
1.1G /usr
2.1G /swapfile
4.3G total
discourse:
# du -hs /var/discourse/ /var/lib/docker/
1.5G /var/discourse/
7.5G /var/lib/docker/
edit: aha, but we’re double-counting, see instead
# du -hxs /var/discourse/ /var/lib/docker/
1.5G /var/discourse/
4.1G /var/lib/docker/
the forum itself, within the above:
201M /var/discourse/shared/standalone/uploads
315M /var/discourse/shared/standalone/postgres_data
930M /var/discourse/shared/standalone/backups
I’m running Ubuntu 18.04 whereas it looks like you’re running something more like 20.04 which is probably bigger.