get_kernel_version() {
	# determine kernel version that will be running in the generated system
	if [ -e "$MODULES_DIR/kernel/ksrc/include/generated/utsrelease.h" ]; then
		# declare kernel version stuff
		declare -rg SYS_UTS_RELEASE=$(grep 'UTS_RELEASE' "$MODULES_DIR/kernel/ksrc/include/generated/utsrelease.h" | awk -F '"' '{print $2}')
		declare -rg SYS_KERNEL=$(echo "$SYS_UTS_RELEASE" | grep -o -E '^[0-9\.]+')
		declare -rg KERNEL_NEW_VERSION="$SYS_UTS_RELEASE"

		# declare path to kernel headers and modules/firmware
		declare -rg KERNEL_HEADERS_PATH="$MODULES_DIR/kernel/ksrc"
		declare -rg KERNEL_BASE_DIR="$MODULES_DIR/kernel/build"
	fi

	# print debug info
	pdebug "SYS_UTS_RELEASE: '$SYS_UTS_RELEASE'"
	pdebug "SYS_KERNEL: '$SYS_KERNEL'"
	pdebug "KERNEL_NEW_VERSION: '$KERNEL_NEW_VERSION'"
	pdebug "KERNEL_BASE_DIR: '$KERNEL_BASE_DIR'"

	# check the headers/src path
}

fetch_source() {
	pdebug "getting kernel sources via git ...."
	[ -d ./ksrc ] && rm -rf ./ksrc			# slightly brutal ...
	git clone --depth 1 "${REQUIRED_GIT}" -b "${REQUIRED_GIT_BRANCH}"  ksrc || perror "Could not clone kernel git."
	# check for aufs
	local RSL=$(find ksrc/ -type d -name aufs)
	if [ -z "$RSL" ]; then
		pinfo "aufs not found in kernel sources, patching it..."
		patch_aufs
	else
		pinfo "aufs detected in kernel source :)"
	fi
	# remember the current kernel version
	echo "${KERNEL_CURRENT_VERSION}" > ksrc/KVERSION
}

build() {
	local TARGET_CONFIG_FILE="openslx.config"
	[ -e "${TARGET_CONFIG_FILE}" ] && rm -f "${TARGET_CONFIG_FILE}"
	# update config and copy to ksrc
	pinfo "Updating kernel config..."
	update_config
	cp "${TARGET_CONFIG_FILE}" ksrc/.config
	# make kernel with the new config
	cd ksrc || perror "Could not cd to ksrc, was the kernel source fetched properly?"
	pinfo "Preparing kernel for new config ('make oldconfig')."
	if [ "x$MLTK_QUIET" = "x1" ]; then
		yes "" | make oldconfig || perror "make oldconfig failed."
	else
		make oldconfig || perror "make oldconfig failed."
	fi
	make prepare || perror "make prepare failed."
	make scripts || perror "make scripts failed."

	pinfo "Compiling kernel... (this will take some time)"
	if gcc --version | grep "4\.7" && which distcc; then
		pinfo "USING DISTCC"
		make CC="distcc gcc-4.7" -j16 || perror "make failed."
	else
		# explicitly state number of cores here, as MAKEFLAGS seems to be overridden
		make "-j$CPU_CORES" || perror "make failed."
	fi
	
	# install modules to build directory
	pinfo "Installing kernel modules..."
	if [ -d "${MODULE_BUILD_DIR}/lib/modules" ]; then
		rm -r "${MODULE_BUILD_DIR}/lib/modules" || pwarning "Could not clean old modules."
	fi
	make INSTALL_MOD_PATH="${MODULE_BUILD_DIR}" INSTALL_MOD_STRIP=1 modules_install || perror "make modules_install failed in ${MODULE_BUILD_DIR}."
	cd - 2> /dev/null

	# copy kernel to build
	cp ksrc/arch/x86/boot/bzImage "${MODULE_BUILD_DIR}/${KERNEL_TARGET_NAME}"
	pinfo "Kernel was successfully built at ${MODULE_BUILD_DIR}/${KERNEL_TARGET_NAME}"
	[ -z "${KERNEL_BUILD_DIR}" ] && KERNEL_BUILD_DIR="${MODULE_BUILD_DIR}"
}

post_copy() {
	:
}

# helper function to update the current kernel config with our parameters
update_config() {

	# first we need to update the current config
	local BASE_CONFIG_FILE="/boot/config-$(uname -r)"
	[ -e "${BASE_CONFIG_FILE}" ] || perror "$BASE_CONFIG_FILE could not be found! This should not happen."
	
	# check for our wanted config parameter
	local OPENSLX_WANTED_CONFIG="${ROOT_DIR}/data/kernel.wanted.config"

	[ -e "${OPENSLX_WANTED_CONFIG}" ] || perror "$OPENSLX_WANTED_CONFIG does not exist! Please add a list of wanted kernel config parameters."

	# copy basic config file
	cp "$BASE_CONFIG_FILE" "$TARGET_CONFIG_FILE"

	for WANTED_CONFIG in $(cat $OPENSLX_WANTED_CONFIG|sort -u); do
		local CONFIG_PARAM_NAME="$(echo $WANTED_CONFIG | awk -F "=" '{print $1}')"
		local SEARCH_RESULT="$(grep -E "^\s*$(echo "$CONFIG_PARAM_NAME" | escape_search)=" "$BASE_CONFIG_FILE")"

		#echo "Process: $SEARCH_RESULT"
		# analyse results
		if [ "x$SEARCH_RESULT" == "x" ]; then
			# no match, add it
			sed -i -r "s/^\s*#.*\s$(echo "$CONFIG_PARAM_NAME" | escape_search)[^_A-Z0-9].*$//" "$TARGET_CONFIG_FILE"
			echo "$WANTED_CONFIG" >> "$TARGET_CONFIG_FILE"
		else
			# match, change to our setting if they differ
			if [ "x$SEARCH_RESULT" != "x$WANTED_CONFIG" ]; then
				sed -i "s/$(echo "$SEARCH_RESULT" | escape_search)/$(echo "$WANTED_CONFIG" | escape_replace)/" "$TARGET_CONFIG_FILE"
			fi
		fi
	done
}

# helper to patch aufs
patch_aufs() {
	pinfo "Cloning aufs3 standalone git"
	cd "$MODULE_DIR"
	[ -d "aufs3-standalone/.git" ] && rm -rf "aufs3-standalone"		# if already there, kill it.
	# git: --depth 1 won't work here due to later "checkout origin/branch"
	git clone "git://aufs.git.sourceforge.net/gitroot/aufs/aufs3-standalone.git" || perror "Cloning aufs3 failed."
	# get the needed version
	[ ! -z ${KERNEL_CURRENT_VERSION} ] && local NEEDED_BRANCH=$(echo $KERNEL_CURRENT_VERSION | awk -F "." '{print $1"."$2}') \
				|| perror "KERNEL_CURRENT_VERSION not set, this should not happen!"
	pinfo "Getting branch origin/$NEEDED_BRANCH"
	cd "$MODULE_DIR/aufs3-standalone" || perror "Could not CD to aufs3-standalone"
	git checkout "origin/aufs$NEEDED_BRANCH" || perror "Could not checkout needed branch."
	pinfo "Starting to patch... $NEEDED_BRANCH"
	tarcopy "Documentation fs" "$MODULE_DIR/ksrc"

	# Quick-and-dirty aufs_type.h copying:
	[ -e "include/linux/aufs_type.h" ] && cp "include/linux/aufs_type.h" "$MODULE_DIR/ksrc/include/linux/"
	[ -e "include/uapi/linux/aufs_type.h" ] && cp "include/uapi/linux/aufs_type.h" "$MODULE_DIR/ksrc/include/uapi/linux/"

	cd "$MODULE_DIR/ksrc" || perror "Could not CD to kernel-source dir ksrc"

	patch -p1 < "$MODULE_DIR/aufs3-standalone/aufs3-kbuild.patch" || perror "aufs3-standalone/aufs3-kbuild.patch failed!"
	patch -p1 < "$MODULE_DIR/aufs3-standalone/aufs3-base.patch" || perror "aufs3-standalone/aufs3-base.patch failed!"

	# this following 'if' is a burning shame - caused as patching under eg. openSuse 13.1 is always unsuccessful due to hunk failing
	if [ -f "$MODULE_DIR/aufs3-standalone/aufs3-mmap.patch" ]; then
			patch -p1 < "$MODULE_DIR/aufs3-standalone/aufs3-mmap.patch" || pwarning "Problem patching aufs3-mmap.patch: hunks failed?"
	fi
	pinfo "Patched kernel source with aufs-${NEEDED_BRANCH}"
	cd "$MODULE_DIR"
}