I recently upgraded my quite old (I think installed around 6 years ago, and upgraded a few times since) installation a few weeks ago. When rebooted it won't boot up with the following grub error:
'error: unknown filesystem'
Upon which it enters rescue mode.
I'm assuming that the issue was introduced by the upgrade, but I can't be sure as the system had been up months before the upgrade.
It's pure Ubuntu. Never been anything else, or dual booted etc.
The install disc has 3 partitions, sda1 / ext4, sda2 swap and sda3 'everything else' - a storage partition mounted under /media which is ext3.
I have a feeling that sda1 / was ext3 before the upgrade, but can't be sure, I don't pay attention to details when they work...
ls (hd0, msdos1) and (hd0, msdos2) returns 'Filesystem is unknown'. ls (hd0, mddos3) returns ext2.
I've booted Gpartd and checked the filesystems. They're all fine. /dev/sda1 is ext4 and has 'boot' flag set, and when mounted looks ok to me. /boot is there, with what look like reasonable contents, but I'm no expert.
I then booted a live USB and ran 'boot-repair'. The output from its last re-install attempt is here:
It fails with a similar error:
" Generating grub configuration file ... grub-probe: error: unknown filesystem.
An error occurred during the repair.
You can now reboot your computer. "
I am now at a loss as to where to go next - this isn't googling very well, I can't find anyone who actually found the root cause of an issue - only cases where a re-install or similar worked. I think I could install grub on a different partition, but that seems to be guesswork to me, rather than based on any evidence.
Any ideas anyone?