My disk is full. I can't login to ssh, even PHP sessions are not working, is there any way I can fix this?
Ubuntu Server 14.04
This cannot be solved through SSH.
Go to the console, boot your iso, change into your home folder, find thumbnails, internet caches and delete them all.
Disable your internet connection because Ubuntu or other programs might fill the the available space with security updates, ... and run out of disk space immediately.
Try to reboot (still offline) and run the normal sudo apt-get remove/purge
to get space, then remove obsolete linux kernels (they can be found in aptitude
under search obsolete or no longer needed packages)!
Reboot again and activate your internet.
It should work now. Be aware that additional removal/purging of the system might be needed! Do find obsolete/unwanted packages and clean them.