fetch_source() {
	# get the source according to the distro
        if [ "x$PACKET_MANAGER" == "xapt" ]; then
		pdebug "apt-ing kernel source"
		apt-get install -y dpkg-dev || perror "Installing dpkg-dev failed."
                apt-get source linux-image-${KERNEL_CURRENT_VERSION} || perror "Fetching kernel source failed."
		[ -z "$(ls -d linux-*/)" ] && perror "Source directory not found."
		[ ! -e ksrc ] && ln -s  "$(ls -d linux-*/)" "ksrc"
        elif [ "x$PACKET_MANAGER" == "xzypper" ]; then
		pdebug "zypping kernel source"
                zypper --no-refresh install -y kernel-source || perror "Fetching kernel source failed."

		# find src directory
		local SOURCE_DIR=$(rpm -ql kernel-source |grep -E -o '^/.*src/linux-[^/]+/' |head -1)
		[ -z "${SOURCE_DIR}" ] && perror "Could not determine directory of kernel source..."
		ln -sf "${SOURCE_DIR}" ksrc
        else
		pdebug "Packet manager not determined!"
	fi

	# 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

	# fix pc speaker
	./patch-speaker

	# 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$MLTK_QUIET" = "x1" ]; then
		yes "" | make oldconfig || perror "make oldconfig failed"
	else
		make oldconfig || perror "make oldconfig failed"
	fi
	pinfo "Compiling kernel... (this will take some time)"
	if gcc --version | grep "4\.7" && which distcc; then
		pinfo "USING DISTCC"
		make CC="distcc gcc-4.7" -j16 || perror "make failed"
	else
		# explicitly state number of cores here, as MAKEFLAGS seems to be overridden
		make "-j$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() {
	mkdir -p "$TARGET_BUILD_DIR/../kernel"
	cp -a "$MODULE_BUILD_DIR/kernel" "$TARGET_BUILD_DIR/../kernel/kernel" || perror "could not copy kernel to remote build dir"
}

# 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"
	if [ ! -d "aufs3-standalone/.git" ]; then
		rm -rf "aufs3-standalone"
		git clone "git://aufs.git.sourceforge.net/gitroot/aufs/aufs3-standalone.git" || perror "Cloning aufs3 failed."
	fi
	# 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"
	pinfo "Starting to patch..."
	tarcopy "Documentation fs" "$MODULE_DIR/ksrc"
	local AUFSH
	if [ ! -e "include/linux/aufs_type.h" ]; then
		[ ! -e "include/uapi/linux/aufs_type.h" ] && perror "No aufs_type.h in aufs3-git"
		AUFSH="include/uapi/linux/aufs_type.h"
	elif [ -e "include/uapi/linux/aufs_type.h" -a "$(stat -c %s "include/uapi/linux/aufs_type.h")" -gt "$(stat -c %s "include/linux/aufs_type.h")" ]; then
		AUFSH="include/uapi/linux/aufs_type.h"
	else
		AUFSH="include/linux/aufs_type.h"
	fi
	pinfo "Using $AUFSH"
	cp "$AUFSH" "$MODULE_DIR/ksrc/include/linux/" || perror "could not copy $AUFSH"
	cd "$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"
	#patch -p1 < "$MODULE_DIR/aufs3-standalone/aufs3-proc_map.patch" || perror "aufs3-standalone/aufs3-proc_map.patch failed"
	pinfo "Patched kernel source with aufs-${NEEDED_BRANCH}"
	cd "$MODULE_DIR"
}