i had this problem recently when i couldn't mount any disk in a read-write mode, just read-only. then i asked here and there about it. made a change or two in that file and now that i restarted the pc, i can't boot into my xubuntu. in the boot device choice screen, it doesn't list my disk with the OS anymore, just a flash drive that's plugged in my usb. i don't even know for sure if this issue is connected to the changes i made to that file.
i already tried checking the cables on the disk, but they seem fine. i was using the pc normally up until 1 hour ago. i did perform a system update though.
edit: trying to boot with the usb boot, suddenly my disk appear as a boot option. i don't know why nor if i will have the same problem again. i still have a problem with opening other disks as read and write mode