Problem : /boot disk has no space, thus blocking installation or removal of any package using apt-get
Fix :
In terminal –
cd /boot
ls
sudo rm -r abi-4.4.0-89-generic abi-4.4.0-92-generic config-4.4.0-89-generic config-4.4.0-92-generic initrd.img-4.4.0-89-generic initrd.img-4.4.0-92-generic System.map-4.4.0-89-generic System.map-4.4.0-92-generic vmlinuz-4.4.0-89-generic vmlinuz-4.4.0-92-generic
(From the listed files, remove least two versions of every file)
This command searches of kernel files not in use and removes them to make space.