linux – Insufficient disk space on file system root error under openSUSE Leap 15

Apparently, I run out of disk space on my root partition. At the time of installation of my operating system (openSUSE Leap 15), I chose the default partitioning. Now, I receive the warning / error Insufficient disk space on the "root of the file system". It warns me when I start the system and when I try to compile a large project, an error is generated.

What's taking up so much space?

$ sudo from -hsx / * | sort -rh | head -n 40
[sudo] password for root:
from: can not access / proc / 8809 / task / 8809 / fd / 4: no file or directory of this type
from: can not access & proc / 8809 / task / 8809 / fdinfo / 4: no such file or directory
of: can not access / proc / 8809 / fd / 4: no file or directory of this type
from: can not access / proc / 8809 / fdinfo / 4: no such file or directory
51G / house
5.5G / usr
972M / opt
894M / var
792M / lib
63M / start
38M / tmp
24M / etc
18M / race
11M / sbin
11M / lib64
2.1 M / bin
320K / root
0 / sys
0 / srv
0 / selinux
0 / proc
0 / mnt
0 / dev

If you wonder what takes up so much space in / usr is my texlive installation, which I would like to keep and make available to other users.

I've also heard of old unused kernels, so check and find this:

$ ls -la / lib / modules
total 0
drwxr-xr-x 1 root root 108 November 8th 09:29 AM.
drwxr-xr-x 1 root root 78 4 Oct 16:13 ..
drwxr-xr-x 1 root root 354 16 October 09:11 4.12.14-lp150.12.22-default
drwxr-xr-x 1 root root 354 November 8th 09:26 4.12.14-lp150.12.25-default
  1. Resize the root partition. (give root 10 more gigs would be nice)
  2. Delete the old version of the kernel and hope that I do not break things and that the 245 MB released will suffice for the moment.

I really prefer to leave more space at the root, but I have no idea how to do it or if it's a good idea to mess it up.