This question already has an answer here:

Plenty of free disk space. How do I either free up space on boot or increase its size? Using release 12.10 (quantal) 64-bit Kernel Linux 3.5.0-26-generic. Thanks, Dave.

marked as duplicate by Rinzwind, Panther, mikewhatever, Eric Carvalho, user83046 Mar 21 '13 at 19:33

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

Delete the old Kernels

sudo apt-get purge $( dpkg --list | grep -P -o "linux-image-\d\S+" | grep -v $(uname -r | grep -P -o ".+\d") )

OR

use Ubuntu tweaks and then run janitor to clear unused packages

http://ubuntu-tweak.com/

Not the answer you're looking for? Browse other questions tagged or ask your own question.