Some way to clean up / identify contents of /var/lib/docker/overlay

Hi all.

I have the same issue, my small docker server was out of space and df shows 100% usage, like

zzz@dovpn:~$ df -h
Filesystem      Size  Used Avail Use% Mounted on
tmpfs            96M  9.6M   87M  10% /run
/dev/vda1        25G   25G     0 100% /
tmpfs           479M     0  479M   0% /dev/shm
tmpfs           5.0M     0  5.0M   0% /run/lock
/dev/vda15      105M  6.1M   99M   6% /boot/efi
overlay          25G   25G     0 100% /var/lib/docker/overlay2/%ID%
tmpfs            96M  4.0K   96M   1% /run/user/1000

So, i’ve found this thread. But all commands like

docker builder prune
docker system prune -a
docker system df -v

Gives me about zero savings and about zero info. I still had out of space state. My next suggestion was to stop docker service and look around. And all my space was vasted by system logs.
du -hd2 /var/log/* | sort -rh | head

Shows me some big logs which eats my disk. So the solution was to truncate | disable logs and that is. For example, in my case
sudo truncate -s 0 /var/log/{syslog,kern.log}

Hope it helps someone.