unix ubuntu clear the full boot

1- get the current version
uname -r

2- check the space in boot
df -h

3- list all installed linux images

dpkg --list | grep linux-image

3- Purge the ones we don’t need any more.  for example  this one "linux-image-3.2.0-23-generic"

sudo apt-get purge linux-image-3.2.0-23-generic

if this command didn't work then try to do it  manually by this

cd /boot
sudo rm -f *-3.5.0-21-*

4-Verify

If everything worked, you can run these commands without errors.

sudo update-grub2 && sudo update-initramfs -u

Then update everything to ensure that our system is clean and up-to-date

sudo aptitude safe-upgrade && sudo reboot now