error no network interface

A full root filesystem ( / is 100% full) is a serious problem. It is unlikely that the server can function normally.

You can possibly fix this by booting from other media and by fixing corrupt filesystems and deleting all the junk(?) files that fill up the root filesystem.

Booting from other media typically means removing the disk/thumb drive/SD card and connect it to a working computer and access the problem filesystem from there. Or booting from a thumbdrive.

There are several possibilities for why this happened. Four possibilities are:

1. Some program malfunctioned or was badly configured and it started writing to the root filesystem and wouldn't stop.

2. A disk that should be mounted at some mount point became unmounted. And you ran some software that was supposed to write to that disk. Instead the writes were written in the mount point on the root filesystem.

3. The root file system is corrupt due to bad media.

4. A disk that should be used is corrupt and can't be mounted.

I guess 2+4 is most likely.

First a disk went bad, then it couldn't be mounted, then the root file system was filled.

You need to fix the corrupt disk. Then delete the files that fill up the root file system.

OMV typically use mount points /sharedfolders and in /srv

If a disk was connected with USB and the cable moved/was touched/the temperature changed/or there was a faint breeze or if there was a problem with sufficient voltage or current, then a disk might spontaneously become unmounted.