Purge unused kernel packages on Ubuntu 14.04

purge.sh

# Get all patch versions of all kernels on the system
all_kernel_patch_versions=$( dpkg -l | egrep 'linux-headers-3.13.0-[0-9]+-generic' | awk -F '-' '{print $4}' | sort -n )

# Exclude any kernels that are in use (hard coded; you must CUSTOMIZE THIS PER MACHINE)
unused_kernel_patch_versions=$( echo "$all_kernel_patch_versions" | egrep -v '1[67]' )  

for n in $unused_kernel_patch_versions ; do 
  echo
  echo "========== $n ========="
  echo
  dpkg --purge linux-image-3.13.0-${n}-generic linux-image-extra-3.13.0-${n}-generic linux-headers-3.13.0-${n}-generic linux-headers-3.13.0-${n}
done