I have this problem, it started without context once when i was trying to start the OS. I use a ssd external disk and its new, so i dont think that the disk is the problem.Secure boot mode disable. When i try to iniciate the OS the above message appears and entry in the emergency mode, where using the commands that provides is useless, but if before typing exit I write "mount -a" and then "exit", it works. I literally dont understand nothing, I dont know what happened, so pls any answer would be appreciated. Thank you.