remove old installed linux kernel (tested on ubuntu releases)

purge-kernels.sh

#!/usr/bin/env bash
# ⚠️ ATTENTION! It purges kernels without asking for confirmation!!!
CURRENT_KERNEL=$(uname -r | grep -oE '[0-9\.]+-[0-9]+')
LATEST_KERNEL=$(apt show linux-image-generic | grep -oE 'linux-image-[0-9\.]+-[0-9]+' | cut -d '-' -f3-)
BASE_KERNEL=$(echo ${CURRENT_KERNEL} | cut -d '.' -f 1-2)
apt list --installed | grep linux  | cut -d '/' -f 1 | egrep -v "(${CURRENT_KERNEL}|${LATEST_KERNEL})" | grep "${BASE_KERNEL}." |  tr '\n' ' ' | xargs apt purge -y