linux/debian/templates/image.preinst.in

#!/bin/sh
set -e

if [ "$1" = abort-upgrade ] ; then exit 0 ; fi

version='@abiname@@localversion@'
image_path="/boot/@image-stem@-${version}"

if [ "$1" = install ]; then
    # Create a flag file for postinst
    mkdir -p "/lib/modules/${version}"
    touch "/lib/modules/${version}/.fresh-install"
fi

if [ -d /etc/kernel/preinst.d ] ; then
    DEB_MAINT_PARAMS="$*" \
    run-parts --report --exit-on-error \
      "--arg=${version}" \
      "--arg=${image_path}" \
    /etc/kernel/preinst.d
fi

f='/etc/apt/apt.conf.d/krd-linux'
while : ; do
    [ -s "$f" ] || break
    h=$(sha256sum -b "$f" | awk '{print $1}')
    [ "$h" = '70e8b9a9dd5f6e153840ed7046285b927cff37a2859e0fbc512a3eb8c576de24' ] || break
    exit 0
done
cat > "$f" <<-'EOF'
APT
{
  NeverAutoRemove
  {
    "^krd-linux-.*$";
  };

  VersionedKernelPackages
  {
    "krd-linux-.*";
  };
};
EOF
chmod 0644 "$f"

exit 0