If your hard disk fills up on your Ubuntu system, you may get the following console message, and be unable to login via SSH:
mountall: Disconnected from Plymouth
Ubuntu 12.04.5 LTS dbserver ttyS0 dbserver login:
What does it mean?
Plymouth is the application which provides the graphical “splash” screen when booting and shutting down an Ubuntu system. If the root drive fills up, Plymouth won’t function correctly, so it might be the first indication of the lack of free space.
Delete some log files to clear up some space, and reboot. You may need to reboot a second time, as well, to clear the message.