delete all old kernels

bash

sudo apt-get purge $(\
  for tag in "linux-image" "linux-headers"; \
    do dpkg-query -W -f'${Package}\n' "$tag-[0-9]*.[0-9]*.[0-9]*" | \
    sort -V | \
    awk 'index($0,c){exit} //' c=$(uname -r | cut -d- -f1,2); \
  done)