The symptom
If apt-get isn’t functioning because your /boot is at 100%, you’ll need to clean out /boot first. This likely has caught a kernel upgrade in a partial install which means apt has pretty much froze up entirely and will keep telling you to run apt-get -f install even though that command keeps failing.
The cause
With a small boot partition and UnAttended upgardes on; a
The solution
Warning: only use this way of cleaning the boot partition when you tried to solve it first with apt-get itself: e.g. sudo dpkg --list 'linux-image*' and then delete unneeded kernels with: sudo apt-get remove linux-image-VERSION replacing VERSION with the linux kernel versions you want to remove.
If that yields an error like:
dpkg: dependency problems prevent removal of linux-image-3.13.0-79-generic: linux-image-extra-3.13.0-79-generic depends on linux-image-3.13.0-79-generic. dpkg: error processing package linux-image-3.13.0-79-generic (--purge): dependency problems - not removing Errors were encountered while processing: linux-image-3.13.0-79-generic
This solution is for you:
List kernels that you can remove
Get the list of kernel images and determine what you can do without. The next command will list all installed kernels .
sudo dpkg --list 'linux-image*'|awk '{ if ($1=="ii") print $2}'|grep -v `uname -r`
Remove unneeded/unwanted kernels
Craft a command to delete all files in /boot for kernels that don’t matter to you using brace expansion to keep you sane. Remember to exclude the current and two newest kernel images. Example:
sudo rm -rf /boot/*-3.13.0-{68,70,71,72,73}-*.
Fix apt
sudo apt-get -f install to clean up what’s making apt grumpy about a partial install.
If you run into an error that includes a line like “Internal Error: Could not find image (/boot/vmlinuz-3.13.0-68-generic)”, then run the command sudo apt-get purge linux-image-3.13.0-68-generic (with your appropriate version).
Finally, sudo apt-get autoremove to clear out the old kernel image packages that have been orphaned by the manual boot clean.
Install updates/upgrades
Optionally: run sudo apt-get update and sudo apt-get upgrade to take care of any upgrades that may have backed up while waiting for you to discover the full /boot partition.
Eliminating the root cause
You can turn on autoremoval of unneeded software after you unattended security updates by uncommentng an option in /etc/apt/apt.conf.d/50unattended-upgrades:
Look for this line:
// Do automatic removal of new unused dependencies after the upgrade
// (equivalent to apt-get autoremove)
Unattended-Upgrade::Remove-Unused-Dependencies "true";
Then apt-get autoremove is executed after each unattended upgrade.
The alternative
Someone wrote a small python program that does this for you: https://github.com/EvanK/ubuntu-purge-kernels Use at your own risk.