#!/bin/bash

# kernel-cleanup.sh - Remove obsolete packages and config files
# {{ ansible_managed }}

# Determine the active running kernel
RUNNING_KERNEL="$( uname -v | awk '{ print $4 }' )"

# Determine the list of installed kernels (latest first)
INSTALLED_KERNEL_PACKAGES=( $( dpkg -l | grep 'linux-image-[0-9]' | awk '{ print $2 }' | sort -Vr ) )
NUM_INSTALLED=${{ '{#' }}INSTALLED_KERNEL_PACKAGES[@]}

if [[ ${NUM_INSTALLED} -le 1 ]]; then
    echo "A single kernel is installed, aborting cleanly."
    exit 0
fi

LATEST_KERNEL_PACKAGE="${INSTALLED_KERNEL_PACKAGES[0]}"
LATEST_KERNEL="$( dpkg -l | grep "${LATEST_KERNEL_PACKAGE}" | awk '{ print $3 }' )" 
if [[ ${LATEST_KERNEL} == ${RUNNING_KERNEL} ]]; then
    force=""
else
    force="--allow-remove-essential"
fi

# Remove the latest kernel from the array
NUM_REMOVABLE=$(( ${NUM_INSTALLED} - 1 ))
REMOVABLE_KERNEL_PACKAGES=( ${INSTALLED_KERNEL_PACKAGES[@]:1} )

# Override the "linux-check-removal" script
mv /usr/bin/linux-check-removal /usr/bin/linux-check-removal.orig
echo -e '#!/bin/sh\necho "Overriding default linux-check-removal script!"\nexit 0' > /usr/bin/linux-check-removal
chmod +x /usr/bin/linux-check-removal

# Remove the packages
echo "Removing: ${REMOVABLE_KERNEL_PACKAGES[@]}"
apt-get purge --yes ${force} ${REMOVABLE_KERNEL_PACKAGES[@]}

# Restore the "linux-check-removal" script
mv /usr/bin/linux-check-removal.orig /usr/bin/linux-check-removal

# Make sure there is still a valid kernel installed (just in case something broke)
if [[ $( dpkg -l | grep 'linux-image-[0-9]' | wc -l ) -lt 1 ]]; then
    echo "WARNING: NO KERNEL IS INSTALLED. THROWING ERROR AND ABORTING."
    exit 1
fi

update-grub

exit 0