Script to remove old linux kernels on debian based distributions

remove_old_kernels.sh

#!/bin/sh -e

# This script will remove all the kernels, except newest $keep_count and the currently active one.
# Very handy with Ubuntus as that installs a lot of kernels.
  
keep_count=${1:-2}

# select versions to keep
installed=$(dpkg -l 'linux-*' | awk '/^ii/ {print $2}' | grep -E "\-[0-9]+\.[0-9]+\.[0-9]+-[0-9]+" -)

keep=$(echo "$installed" | sed -e 's/^[^0-9]\+-//g' -e 's/\(-[0-9]\+\)-[a-z].*$/\1/g' | sort -uVr | head -n $keep_count)
rule=$(echo "$keep" | xargs -L1 -I% echo "/%/d;" | tr -d '\n')

current=$(uname -r | sed -e 's/\(-[0-9]\+\)-[a-z].*$/\1/g')
to_remove=$(echo "$installed" | sed "$rule/$current/d")

if [ "$to_remove" ]; then
    dpkg -P $to_remove
else
    echo "Nothing to remove"
fi