Remove Old Kernels via DPKG

If your /boot partition has already full while doing an upgrade or package install, and apt (the script above uses apt) can’t remove packages due to broken dependency, here you can manually find out the old kernel packages and remove them via DPKG:
1. Run command to check out current kernel and DON’T REMOVE it:

uname -r

2. List all kernels excluding the current booted:

dpkg -l | tail -n +6 | grep -E 'linux-image-[0-9]+' | grep -Fv $(uname -r)

Example output:

rc  linux-image-4.4.0-15-generic               4.4.0-15.31                                         amd64        Linux kernel image for version 4.4.0 on 64 bit x86 SMP
ii  linux-image-4.4.0-18-generic               4.4.0-18.34                                         amd64        Linux kernel image for version 4.4.0 on 64 bit x86 SMP
rc  linux-image-4.6.0-040600rc3-generic        4.6.0-040600rc3.201604120934                        amd64        Linux kernel image for version 4.6.0 on 64 bit x86 SMP

There will be three status in the listed kernel images:

• rc: means it has already been removed.
• ii: means installed, eligible for removal.
• iU: DON’T REMOVE. It means not installed, but queued for install in apt.

3. Lsit all kernels that can deleted
dpkg -l linux-image-\* | grep ^ii
4. Remove old kernel images in status ii, it’s “linux-image-4.4.0-18-generic” in the example above:

sudo dpkg --purge linux-image-4.4.0-18-generic

If the command fails, remove the dependency packages that the output tells you via sudo dpkg --purge PACKAGE.
And also try to remove the respective header and common header packages (Don’t worry if the command fails):

sudo dpkg --purge linux-image-4.4.0-18-header linux-image-4.4.0-18

5. Finally you may fix the apt broken dependency via command:

sudo apt -f install