+# check if the specified Debian package exists
+package_exists() {
+ output=$(apt-cache show "$1" 2>/dev/null)
+ [ -n "$output" ]
+ return $?
+}
+
+
+# determine the kernel version postfix
+get_kernel_version() {
+ # do not override $KERNEL if set via config file
+ if [ -n "$KERNEL" ] ; then
+ echo "$KERNEL"
+ return 0
+ fi
+
+ local KARCH
+
+ # shellcheck disable=SC2153
+ case "$ARCH" in
+ i386)
+ case "$RELEASE" in
+ lenny|squeeze|wheezy) KARCH='686' ;;
+ # since jessie the linux-image-686 image doesn't exist any longer
+ *) KARCH='686-pae' ;;
+ esac
+ ;;
+ amd64)
+ KARCH='amd64'
+ ;;
+ *)
+ echo "Only i386 and amd64 are currently supported" >&2
+ return 1
+ esac
+
+ for KPREFIX in "" "2.6-" ; do # iterate through the kernel prefixes,
+ # currently "" and "2.6-"
+ if package_exists linux-image-${KPREFIX}${KARCH} ; then
+ echo ${KPREFIX}${KARCH}
+ return 0
+ fi
+
+ done
+}
+