My disk space is suddenly gone and nowhere to be found

A couple of days ago I got a notification, that my storage space was full. It happened about a week after I transferred to a new machine. (from x86 to x86) Both were running HASS supervised on Ubuntu, and the new one is a completely fresh install. (I know that ubuntu isn’t supported but it never caused any trouble. Possibly until now.) The transfer was done using a backup and I had no apparent problems.
Now, my space is gone. It’s not backups, it’s not the database. but almost 100 gigs are gone. HASS is the only major program on the system.
I will be very glad for any help.

out of control log file?

Log files sounds reasonable indeed, did you try to analyse the distribution of data?
e.g. below would give you some info (2nd one limits to top- 20)

du -hx | sort -rh | head -20

Has is just went missing, or has it always been gone?
Maybe not the whole size of the disk is mounted??

It is posible that i didn’t mount it properly. I did have some trouble while installing. I may reinstall the whole thing later. But still 100 Gb should be plenty for HASS.

I’ve checked but it’s not it. My home-assistant.log is only 17Mb.

So what I read is that you have LVM installed of about 100G and indeed, this should be fine for most HA installs (depends on number of add-ons and db)
The du allows you to dig into the various ‘folders’ … can you run this from the root and then find out which uses most and gradually dig deeper? Note that you may get overlapping results

And if you want to know more about du… then this is a nice example (without needing to go through --help I mean)
How to Find Top Directories and Files (Disk Space) in Linux (