3 days ago I setup fail2ban. Nothing fancy, just reading the logs of my docker containers where it applied.

Then 2 days ago my server crashed out of nowhere, nothing in the f2b logs (I thought I had banned the entire internet by mistake), doing a nap just tells me port 80 and 443 were open (a few more should have been for Plex).

The same happened yesterday and I pulled the cable just in case I was being hacked (I'm paranoid but not too much), and looked in it. usually I ssh from my local network into the server, but couldn't this time, so I put a screen on it and it was quickly flooded with systemd failures and ext4 errors.

I reformated the disk a few months ago and ran a SMART, it told me the disk was fine, no error detected. It is a chonky 2TB disk and I have at most 150gigs used (movies, music, backups waiting to be transferred on daily basis to other servers/media, dockers).

Where should I look? I know how to work with Linux but when looking for a problem like this, except using systemctl status/restart I'm lost.