What to do if the ubuntu root partition is full and it won't start?

Question

ubuntu

HDD 70gb. And he was all overwhelmed. In the morning, the computer showed an error that 0 bytes are free on the bug. Ubuntu won't start after reboot. I tried deleting files through the grub console - and he says that he does not know the rm command.

Answer 1

Boot from livecd, mount disk and clean.

Answer 2

Hold Shift while booting to get to the Grub bootloader menu.
In it choose:
After that, you can still go to the point

root (Drop to root shell prompt)

and delete some files manually.