My system is split into two LVM partitions, one for / and one for /home. Before I install anything dangerous, I always create a snapshot of the / first.
I wanted some way to check the GPU temperature on my nvidia GPU and I found an upvoted answer on askubuntu recommending that I install nvidia-smi to achieve this feat. So I made the snapshot and then installed nvidia-smi. This turned out to be a big mistake, after rebooting, the login screen was in a small resolution and when I tried to log in I got a black screen and 5 seconds later was returned back to the login screen every time.
No big deal I thought, this is why I made the snapshot after all.
So I logged in over SSH which still worked, suggesting that only GUI was broken, and executed the merging command
lvconvert --merge /dev/main/systemSnapshot
The terminal replied that it can't do it right now, because the system is mounted and will do it on the next reboot. This is fine, I restored / snapshots like that several times before.
So I rebooted and was welcomed by the login screen in full resolution and everything seemed to be back in order, just as expected... that is until I tried to log in. Black screen... and then 5 seconds later thrown back onto the login screen as before.
How is this possible? The snapshot completely reversed the mess which nvidia-smi created, so how can it be still broken?
I thought that maybe the nvidia-smi created some nasty files in my home folder that were causing this, so I deleted most of the .dot files there but it had no effect.
So my question is, how is it possible that restoring the snapshot didn't fix the issue? I always felt safe knowing that I had a / snapshot running, which could easily undo any of my screw ups and now this feeling of safety was ripped away from me. I mean, snapshots are the only reason why I even use LVM.
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