Original: http://ubuntuguide.net/one-command-to-remove-ubuntu-old-kernels-from-grub If you are running regularly update in your system,the old kernel left behind when ubuntu installs a new linux kernel.The old kernels leave in grub menu,so grub becomes longer and longer. You can check which kernel you are running by this command: uname -r Then use this command to remove unused kernels as well as in grub menu: sudo aptitude purge ~ilinux-image-.*\(\!`uname -r`\) Old way: http://www.linuxreaders.com/2009/08/08/remove-old-kernel-from-ubuntu/