Ubuntu old kernel cleanup

kernel-cleanup.sh

#!/bin/sh
# Cleanup all old kernels and associated packages from the system

set -x

IFS='
'

# more than 1 might very well be broken!
retention=1

disablegrubhook() {
  [ -d /etc/kernel.bak ] || mkdir /etc/kernel.bak
  [ -f /etc/kernel/postrm.d/zz-update-grub ] && mv -f /etc/kernel/postrm.d/zz-update-grub /etc/kernel.bak/zz-update-grub-postrm
  [ -f /etc/kernel/postinst.d/zz-update-grub ] && mv -f /etc/kernel/postinst.d/zz-update-grub /etc/kernel.bak/zz-update-grub-postinst
  [ -f /etc/kernel-img.conf ] && mv -f /etc/kernel-img.conf /etc/kernel.bak && sed 's/^\(postrm_hook   = update-grub\)$/#\1/' /etc/kernel.bak/kernel-img.conf > /etc/kernel-img.conf
}

enablegrubhook() {
  [ -f /etc/kernel.bak/zz-update-grub-postrm -a ! -f /etc/kernel/postrm.d/zz-update-grub ] && mv /etc/kernel.bak/zz-update-grub-postrm /etc/kernel/postrm.d
  [ -f /etc/kernel.bak/zz-update-grub-postinst -a ! -f /etc/kernel/postinst.d/zz-update-grub ] && mv /etc/kernel.bak/zz-update-grub-postinst /etc/kernel/postinst.d
  [ -f /etc/kernel.bak/kernel-img.conf ] && mv -f /etc/kernel.bak/kernel-img.conf /etc/kernel-img.conf
  rm -fr /etc/kernel.bak
}

# Take the list of linux* packages
#  - cut out current kernel
#  - cut out un installed packages
#  - cut out irrelevant pkgs
#  - cut out the package names
#  - version sorted
pkgs=$(dpkg -l linux* | sed \
        -e "/$(uname -r | cut -d- -f1,2)/d" \
        -e '/^un/d' \
        -e '/-\(libc\|headers\|restricted\|crash\|firm\)/d' \
        -e '/^\([a-z]\{2\}[[:space:]]\+\)/!d' \
        -e 's|^[a-z]\{2\}[[:space:]]\+||g;s|[[:space:]]\+.*||g' \
        -e '/[0-9]\+/!d' \
     | sort -Vu)

# linux-image-3.123 etc
imgs=$(echo "$pkgs" | grep '^linux-image-[0-9]' | head -n -$retention)

# all others, ordered by linux-image-generic etc.
pkgs=$(for class in $(echo "$pkgs" | grep -v '^linux-image-[0-9]' | cut -d- -f1,2,3 | sort -u)
       do echo "$pkgs" | grep ^$class | head -n -$retention; done )

# Leave when nothings' to be done
[ -n "$pkgs" -o -n "$imgs" ] || exit 0

echo "Cleaning up obsolete kernel packages..."

# Disable the hooks while we're running to speed things up
disablegrubhook

echo "$pkgs\n$imgs"| xargs dpkg -P

enablegrubhook
update-grub