diff --git a/lib/functions/main/build-packages.sh b/lib/functions/main/build-packages.sh
new file mode 100644
index 000000000..39d215064
--- /dev/null
+++ b/lib/functions/main/build-packages.sh
@@ -0,0 +1,144 @@
+function main_default_build_packages() {
+	# early cleaning for sources, since fetch_and_build_host_tools() uses it.
+	if [[ "${CLEAN_LEVEL}" == *sources* ]]; then
+		LOG_SECTION="cleaning_early_sources" do_with_logging general_cleaning "sources"
+	fi
+
+	# Too many things being done. Allow doing only one thing. For core development, mostly.
+	# Also because "KERNEL_ONLY=yes" should really be spelled "PACKAGES_ONLY=yes"
+	local do_build_uboot="yes" do_build_kernel="yes" exit_after_kernel_build="no" exit_after_uboot_build="no" do_host_tools="yes"
+	if [[ "${JUST_UBOOT}" == "yes" && "${JUST_KERNEL}" == "yes" ]]; then
+		exit_with_error "User of build system" "can't make up his mind about JUST_KERNEL or JUST_UBOOT"
+	elif [[ "${JUST_UBOOT}" == "yes" ]]; then
+		display_alert "JUST_KERNEL set to yes" "Building only kernel and exiting after that" "debug"
+		do_build_uboot="yes"
+		do_host_tools="${INSTALL_HOST_TOOLS:-yes}" # rkbin, fips, etc.
+		exit_after_uboot_build="yes"
+	elif [[ "${JUST_KERNEL}" == "yes" ]]; then
+		display_alert "JUST_KERNEL set to yes" "Building only kernel and exiting after that" "debug"
+		do_build_uboot="no"
+		exit_after_kernel_build="yes"
+		do_host_tools="no"
+	fi
+
+	# ignore updates help on building all images - for internal purposes
+	if [[ "${IGNORE_UPDATES}" != "yes" ]]; then
+
+		# Fetch and build the host tools (via extensions)
+		if [[ "${do_host_tools}" == "yes" ]]; then
+			LOG_SECTION="fetch_and_build_host_tools" do_with_logging fetch_and_build_host_tools
+		fi
+
+		LOG_SECTION="clean_deprecated_mountpoints" do_with_logging clean_deprecated_mountpoints
+
+		for cleaning_fragment in $(tr ',' ' ' <<< "${CLEAN_LEVEL}"); do
+			if [[ $cleaning_fragment != sources ]] && [[ $cleaning_fragment != none ]] && [[ $cleaning_fragment != make* ]]; then
+				LOG_SECTION="cleaning_${cleaning_fragment}" do_with_logging general_cleaning "${cleaning_fragment}"
+			fi
+		done
+	fi
+
+	# Prepare ccache, cthreads, etc for the build
+	LOG_SECTION="prepare_compilation_vars" do_with_logging prepare_compilation_vars
+
+	if [[ "${do_build_uboot}" == "yes" ]]; then
+		# Don't build u-boot at all if the BOOTCONFIG is 'none'.
+		if [[ "${BOOTCONFIG}" != "none" ]]; then
+			# @TODO: refactor this. we use it very often
+			# Compile u-boot if packed .deb does not exist or use the one from repository
+			if [[ ! -f "${DEB_STORAGE}"/${CHOSEN_UBOOT}_${REVISION}_${ARCH}.deb || "${UBOOT_IGNORE_DEB}" == "yes" ]]; then
+				if [[ -n "${ATFSOURCE}" && "${ATFSOURCE}" != "none" && "${REPOSITORY_INSTALL}" != *u-boot* ]]; then
+					LOG_SECTION="compile_atf" do_with_logging compile_atf
+				fi
+				# @TODO: refactor this construct. we use it too many times.
+				if [[ "${REPOSITORY_INSTALL}" != *u-boot* || "${UBOOT_IGNORE_DEB}" == "yes" ]]; then
+					declare uboot_git_revision="not_determined_yet"
+					LOG_SECTION="uboot_prepare_git" do_with_logging_unless_user_terminal uboot_prepare_git
+					LOG_SECTION="compile_uboot" do_with_logging compile_uboot
+				fi
+			fi
+		fi
+		if [[ "${exit_after_uboot_build}" == "yes" ]]; then
+			display_alert "Exiting after u-boot build" "JUST_UBOOT=yes" "info"
+			exit 0
+		fi
+	fi
+
+	# Compile kernel if packed .deb does not exist or use the one from repository
+	if [[ "${do_build_kernel}" == "yes" ]]; then
+		if [[ ! -f ${DEB_STORAGE}/${CHOSEN_KERNEL}_${REVISION}_${ARCH}.deb || "${KERNEL_IGNORE_DEB}" == "yes" ]]; then
+			if [[ -n $KERNELSOURCE ]] && [[ "${REPOSITORY_INSTALL}" != *kernel* ]]; then
+				compile_kernel # This handles its own logging sections.
+			fi
+		fi
+		if [[ "${exit_after_kernel_build}" == "yes" ]]; then
+			display_alert "Only building kernel and exiting" "JUST_KERNEL=yes" "debug"
+			exit 0
+		fi
+	fi
+
+	# Compile armbian-config if packed .deb does not exist or use the one from repository
+	if [[ ! -f ${DEB_STORAGE}/armbian-config_${REVISION}_all.deb ]]; then
+		if [[ "${REPOSITORY_INSTALL}" != *armbian-config* ]]; then
+			LOG_SECTION="compile_armbian-config" do_with_logging compile_armbian-config
+		fi
+	fi
+
+	# Compile armbian-zsh if packed .deb does not exist or use the one from repository
+	if [[ ! -f ${DEB_STORAGE}/armbian-zsh_${REVISION}_all.deb ]]; then
+		if [[ "${REPOSITORY_INSTALL}" != *armbian-zsh* ]]; then
+			LOG_SECTION="compile_armbian-zsh" do_with_logging compile_armbian-zsh
+		fi
+	fi
+
+	# Compile plymouth-theme-armbian if packed .deb does not exist or use the one from repository
+	if [[ ! -f ${DEB_STORAGE}/plymouth-theme-armbian_${REVISION}_all.deb ]]; then
+		if [[ "${REPOSITORY_INSTALL}" != *plymouth-theme-armbian* ]]; then
+			LOG_SECTION="compile_plymouth_theme_armbian" do_with_logging compile_plymouth_theme_armbian
+		fi
+	fi
+
+	# Compile armbian-firmware if packed .deb does not exist or use the one from repository
+	if ! ls "${DEB_STORAGE}/armbian-firmware_${REVISION}_all.deb" 1> /dev/null 2>&1 || ! ls "${DEB_STORAGE}/armbian-firmware-full_${REVISION}_all.deb" 1> /dev/null 2>&1; then
+		if [[ "${REPOSITORY_INSTALL}" != *armbian-firmware* ]]; then
+			compile_firmware_light_and_possibly_full # this has its own logging sections
+		fi
+	fi
+
+	overlayfs_wrapper "cleanup"
+
+	# create board support package
+	if [[ -n "${RELEASE}" && ! -f "${DEB_STORAGE}/${BSP_CLI_PACKAGE_FULLNAME}.deb" && "${REPOSITORY_INSTALL}" != *armbian-bsp-cli* ]]; then
+		LOG_SECTION="create_board_package" do_with_logging create_board_package
+	fi
+
+	# create desktop package
+	if [[ -n "${RELEASE}" && "${DESKTOP_ENVIRONMENT}" && ! -f "${DEB_STORAGE}/$RELEASE/${CHOSEN_DESKTOP}_${REVISION}_all.deb" && "${REPOSITORY_INSTALL}" != *armbian-desktop* ]]; then
+		LOG_SECTION="create_desktop_package" do_with_logging create_desktop_package
+	fi
+	if [[ -n "${RELEASE}" && "${DESKTOP_ENVIRONMENT}" && ! -f "${DEB_STORAGE}/${RELEASE}/${BSP_DESKTOP_PACKAGE_FULLNAME}.deb" && "${REPOSITORY_INSTALL}" != *armbian-bsp-desktop* ]]; then
+		LOG_SECTION="create_bsp_desktop_package" do_with_logging create_bsp_desktop_package
+	fi
+
+	# @TODO: dead code, remove
+	## DEAD CODE IN ARMBIAN-NEXT ## # build additional packages
+	## DEAD CODE IN ARMBIAN-NEXT ## if [[ $EXTERNAL_NEW == compile ]]; then
+	## DEAD CODE IN ARMBIAN-NEXT ## 	display_alert "Building external packages" "$EXTERNAL - WARNING: this has not been armbian-nextifed yet and will fail." "warn"
+	## DEAD CODE IN ARMBIAN-NEXT ## 	exit_with_error "buildpkg chroot_build_packages() nas not been ported to armbian-next yet, rpardini is a bum"
+	## DEAD CODE IN ARMBIAN-NEXT ## 	LOG_SECTION="chroot_build_packages" do_with_logging chroot_build_packages
+	## DEAD CODE IN ARMBIAN-NEXT ## fi
+
+	# Reset owner of DEB_STORAGE, if needed. Might be a lot of packages there, but such is life.
+	# @TODO: might be needed also during 'cleanup': if some package fails, the previous package might be left owned by root.
+	reset_uid_owner "${DEB_STORAGE}"
+
+	# end of kernel-only, so display what was built.
+	if [[ "${KERNEL_ONLY}" != "yes" ]]; then
+		display_alert "Kernel build done" "@host" "target-reached"
+		display_alert "Target directory" "${DEB_STORAGE}/" "info"
+		display_alert "File name" "${CHOSEN_KERNEL}_${REVISION}_${ARCH}.deb" "info"
+	fi
+
+	# At this point, the WORKDIR should be clean. Add debug info.
+	debug_tmpfs_show_usage "AFTER ALL PKGS BUILT"
+}
diff --git a/lib/functions/main/default-build.sh b/lib/functions/main/default-build.sh
index 20b64f414..e800f9fbe 100644
--- a/lib/functions/main/default-build.sh
+++ b/lib/functions/main/default-build.sh
@@ -1,220 +1,21 @@
 # This does NOT run under the logging manager. We should invoke the do_with_logging wrapper for
-# strategic parts of this. Attention: rootfs does it's own logging, so just let that be.
+# strategic parts of this. Attention: almost everything does it's own logging.
 function main_default_build_single() {
-	wait_for_disk_sync "before starting build" # fsync, wait for disk to sync, and then continue. alert user if takes too long.
+	main_default_start_build # Has its own logging, prepares workdir, does prepare_host, aggregation, and
 
-	# Check that WORKDIR_BASE_TMP exists; if not, create it.
-	if [[ ! -d "${WORKDIR_BASE_TMP}" ]]; then
-		mkdir -p "${WORKDIR_BASE_TMP}"
-	fi
+	main_default_build_packages # has its own logging sections # requires aggregation
 
-	# Check the sanity of WORKDIR_BASE_TMP regarding mount options.
-	LOG_SECTION="check_dir_for_mount_options" do_with_logging check_dir_for_mount_options "${WORKDIR_BASE_TMP}" "main temporary dir"
-
-	# Starting work. Export TMPDIR, which will be picked up by all `mktemp` invocations hopefully.
-	# Runner functions in logging/runners.sh will explicitly unset TMPDIR before invoking chroot.
-	# Invoking chroot directly will fail in subtle ways, so, please use the runner.sh functions.
-	display_alert "Starting single build, exporting TMPDIR" "${WORKDIR}" "debug"
-	LOG_SECTION="prepare_tmpfs_workdir" do_with_logging prepare_tmpfs_for "WORKDIR" "${WORKDIR}" # this adds its own cleanup handler, which deletes it if it was created
-	add_cleanup_handler trap_handler_cleanup_workdir                                             # this is for when it is NOT a tmpfs, for any reason; it does not delete the dir itself.
-
-	# 'declare -g -x': global, export
-	declare -g -x TMPDIR="${WORKDIR}"                    # TMPDIR is default for a lot of stuff, but...
-	declare -g -x CCACHE_TEMPDIR="${WORKDIR}/ccache_tmp" # Export CCACHE_TEMPDIR, under Workdir, which is hopefully under tmpfs. Thanks @the-Going for this.
-	declare -g -x XDG_RUNTIME_DIR="${WORKDIR}/xdg_tmp"   # XDG_RUNTIME_DIR is used by the likes of systemd/freedesktop centric apps.
-
-	declare start
-	start=$(date +%s)
-
-	### Write config summary
-	LOG_SECTION="config_summary" do_with_logging write_config_summary_output_file
-
-	# Check and install dependencies, directory structure and settings
-	prepare_host # this has its own logging sections, and is possibly interactive.
-
-	# Aggregate packages, in its own logging section; this decides internally on KERNEL_ONLY=no
-	LOG_SECTION="aggregate_packages" do_with_logging aggregate_packages
-
-	# Create a directory inside WORKDIR with a "python" symlink to "/usr/bin/python2"; add it to PATH first.
-	BIN_WORK_DIR="${WORKDIR}/bin"
-	# No cleanup of this is necessary, since it's inside WORKDIR.
-	mkdir -p "${BIN_WORK_DIR}"
-	ln -s "/usr/bin/python2" "${BIN_WORK_DIR}/python"
-	export PATH="${BIN_WORK_DIR}:${PATH}"
-
-	if [[ "${JUST_INIT}" == "yes" ]]; then
-		exit 0
-	fi
-
-	if [[ $CLEAN_LEVEL == *sources* ]]; then
-		# early cleaning for sources, since fetch_and_build_host_tools() uses it.
-		LOG_SECTION="cleaning_early_sources" do_with_logging general_cleaning "sources"
-	fi
-
-	# Too many things being done. Allow doing only one thing. For core development, mostly.
-	# Also because "KERNEL_ONLY=yes" should really be spelled "PACKAGES_ONLY=yes"
-	local do_build_uboot="yes" do_build_kernel="yes" exit_after_kernel_build="no" exit_after_uboot_build="no" do_host_tools="yes"
-	if [[ "${JUST_UBOOT}" == "yes" && "${JUST_KERNEL}" == "yes" ]]; then
-		exit_with_error "User of build system" "can't make up his mind about JUST_KERNEL or JUST_UBOOT"
-	elif [[ "${JUST_UBOOT}" == "yes" ]]; then
-		display_alert "JUST_KERNEL set to yes" "Building only kernel and exiting after that" "debug"
-		do_build_uboot="yes"
-		do_host_tools="${INSTALL_HOST_TOOLS:-yes}" # rkbin, fips, etc.
-		exit_after_uboot_build="yes"
-	elif [[ "${JUST_KERNEL}" == "yes" ]]; then
-		display_alert "JUST_KERNEL set to yes" "Building only kernel and exiting after that" "debug"
-		do_build_uboot="no"
-		exit_after_kernel_build="yes"
-		do_host_tools="no"
-	fi
-
-	# ignore updates help on building all images - for internal purposes
-	if [[ $IGNORE_UPDATES != yes ]]; then
-
-		# Fetch and build the host tools (via extensions)
-		if [[ "${do_host_tools}" == "yes" ]]; then
-			LOG_SECTION="fetch_and_build_host_tools" do_with_logging fetch_and_build_host_tools
-		fi
-
-		LOG_SECTION="clean_deprecated_mountpoints" do_with_logging clean_deprecated_mountpoints
-
-		for cleaning_fragment in $(tr ',' ' ' <<< "${CLEAN_LEVEL}"); do
-			if [[ $cleaning_fragment != sources ]] && [[ $cleaning_fragment != none ]] && [[ $cleaning_fragment != make* ]]; then
-				LOG_SECTION="cleaning_${cleaning_fragment}" do_with_logging general_cleaning "${cleaning_fragment}"
-			fi
-		done
-	fi
-
-	# Prepare ccache, cthreads, etc for the build
-	LOG_SECTION="prepare_compilation_vars" do_with_logging prepare_compilation_vars
-
-	if [[ "${do_build_uboot}" == "yes" ]]; then
-		# Don't build u-boot at all if the BOOTCONFIG is 'none'.
-		if [[ "${BOOTCONFIG}" != "none" ]]; then
-			# @TODO: refactor this. we use it very often
-			# Compile u-boot if packed .deb does not exist or use the one from repository
-			if [[ ! -f "${DEB_STORAGE}"/${CHOSEN_UBOOT}_${REVISION}_${ARCH}.deb || "${UBOOT_IGNORE_DEB}" == "yes" ]]; then
-				if [[ -n "${ATFSOURCE}" && "${ATFSOURCE}" != "none" && "${REPOSITORY_INSTALL}" != *u-boot* ]]; then
-					LOG_SECTION="compile_atf" do_with_logging compile_atf
-				fi
-				# @TODO: refactor this construct. we use it too many times.
-				if [[ "${REPOSITORY_INSTALL}" != *u-boot* || "${UBOOT_IGNORE_DEB}" == "yes" ]]; then
-					declare uboot_git_revision="not_determined_yet"
-					LOG_SECTION="uboot_prepare_git" do_with_logging_unless_user_terminal uboot_prepare_git
-					LOG_SECTION="compile_uboot" do_with_logging compile_uboot
-				fi
-			fi
-		fi
-		if [[ "${exit_after_uboot_build}" == "yes" ]]; then
-			display_alert "Exiting after u-boot build" "JUST_UBOOT=yes" "info"
-			exit 0
-		fi
-	fi
-
-	# Compile kernel if packed .deb does not exist or use the one from repository
-	if [[ "${do_build_kernel}" == "yes" ]]; then
-		if [[ ! -f ${DEB_STORAGE}/${CHOSEN_KERNEL}_${REVISION}_${ARCH}.deb || "${KERNEL_IGNORE_DEB}" == "yes" ]]; then
-			if [[ -n $KERNELSOURCE ]] && [[ "${REPOSITORY_INSTALL}" != *kernel* ]]; then
-				compile_kernel # This handles its own logging sections.
-			fi
-		fi
-		if [[ "${exit_after_kernel_build}" == "yes" ]]; then
-			display_alert "Only building kernel and exiting" "JUST_KERNEL=yes" "debug"
-			exit 0
-		fi
-	fi
-
-	# Compile armbian-config if packed .deb does not exist or use the one from repository
-	if [[ ! -f ${DEB_STORAGE}/armbian-config_${REVISION}_all.deb ]]; then
-		if [[ "${REPOSITORY_INSTALL}" != *armbian-config* ]]; then
-			LOG_SECTION="compile_armbian-config" do_with_logging compile_armbian-config
-		fi
-	fi
-
-	# Compile armbian-zsh if packed .deb does not exist or use the one from repository
-	if [[ ! -f ${DEB_STORAGE}/armbian-zsh_${REVISION}_all.deb ]]; then
-		if [[ "${REPOSITORY_INSTALL}" != *armbian-zsh* ]]; then
-			LOG_SECTION="compile_armbian-zsh" do_with_logging compile_armbian-zsh
-		fi
-	fi
-
-	# Compile plymouth-theme-armbian if packed .deb does not exist or use the one from repository
-	if [[ ! -f ${DEB_STORAGE}/plymouth-theme-armbian_${REVISION}_all.deb ]]; then
-		if [[ "${REPOSITORY_INSTALL}" != *plymouth-theme-armbian* ]]; then
-			LOG_SECTION="compile_plymouth_theme_armbian" do_with_logging compile_plymouth_theme_armbian
-		fi
-	fi
-
-	# Compile armbian-firmware if packed .deb does not exist or use the one from repository
-	if ! ls "${DEB_STORAGE}/armbian-firmware_${REVISION}_all.deb" 1> /dev/null 2>&1 || ! ls "${DEB_STORAGE}/armbian-firmware-full_${REVISION}_all.deb" 1> /dev/null 2>&1; then
-		if [[ "${REPOSITORY_INSTALL}" != *armbian-firmware* ]]; then
-			compile_firmware_light_and_possibly_full # this has its own logging sections
-		fi
-	fi
-
-	overlayfs_wrapper "cleanup"
-
-	# create board support package
-	if [[ -n "${RELEASE}" && ! -f "${DEB_STORAGE}/${BSP_CLI_PACKAGE_FULLNAME}.deb" && "${REPOSITORY_INSTALL}" != *armbian-bsp-cli* ]]; then
-		LOG_SECTION="create_board_package" do_with_logging create_board_package
-	fi
-
-	# create desktop package
-	if [[ -n "${RELEASE}" && "${DESKTOP_ENVIRONMENT}" && ! -f "${DEB_STORAGE}/$RELEASE/${CHOSEN_DESKTOP}_${REVISION}_all.deb" && "${REPOSITORY_INSTALL}" != *armbian-desktop* ]]; then
-		LOG_SECTION="create_desktop_package" do_with_logging create_desktop_package
-	fi
-	if [[ -n "${RELEASE}" && "${DESKTOP_ENVIRONMENT}" && ! -f "${DEB_STORAGE}/${RELEASE}/${BSP_DESKTOP_PACKAGE_FULLNAME}.deb" && "${REPOSITORY_INSTALL}" != *armbian-bsp-desktop* ]]; then
-		LOG_SECTION="create_bsp_desktop_package" do_with_logging create_bsp_desktop_package
-	fi
-
-	# skip image creation if exists. useful for CI when making a lot of images @TODO: hmm?
-	if [ "$IMAGE_PRESENT" == yes ] && ls "${FINALDEST}/${VENDOR}_${REVISION}_${BOARD^}_${RELEASE}_${BRANCH}_${VER/-$LINUXFAMILY/}${DESKTOP_ENVIRONMENT:+_$DESKTOP_ENVIRONMENT}"*.xz 1> /dev/null 2>&1; then
-		display_alert "Skipping image creation" "image already made - IMAGE_PRESENT is set" "wrn"
-		exit
-	fi
-
-	# @TODO: dead code, remove
-	## DEAD CODE IN ARMBIAN-NEXT ## # build additional packages
-	## DEAD CODE IN ARMBIAN-NEXT ## if [[ $EXTERNAL_NEW == compile ]]; then
-	## DEAD CODE IN ARMBIAN-NEXT ## 	display_alert "Building external packages" "$EXTERNAL - WARNING: this has not been armbian-nextifed yet and will fail." "warn"
-	## DEAD CODE IN ARMBIAN-NEXT ## 	exit_with_error "buildpkg chroot_build_packages() nas not been ported to armbian-next yet, rpardini is a bum"
-	## DEAD CODE IN ARMBIAN-NEXT ## 	LOG_SECTION="chroot_build_packages" do_with_logging chroot_build_packages
-	## DEAD CODE IN ARMBIAN-NEXT ## fi
-
-	# Reset owner of DEB_STORAGE, if needed. Might be a lot of packages there, but such is life.
-	# @TODO: might be needed also during 'cleanup': if some package fails, the previous package might be left owned by root.
-	reset_uid_owner "${DEB_STORAGE}"
-
-	# end of kernel-only, so display what was built.
-	if [[ $KERNEL_ONLY != yes ]]; then
-		display_alert "Kernel build done" "@host" "target-reached"
-		display_alert "Target directory" "${DEB_STORAGE}/" "info"
-		display_alert "File name" "${CHOSEN_KERNEL}_${REVISION}_${ARCH}.deb" "info"
-	fi
-
-	# At this point, the WORKDIR should be clean. Add debug info.
-	debug_tmpfs_show_usage "AFTER ALL PKGS BUILT"
-
-	# build rootfs, if not only kernel.
-	if [[ $KERNEL_ONLY != yes ]]; then
+	# build rootfs, if not only kernel. Again, read "KERNEL_ONLY" as if it was "PACKAGES_ONLY"
+	if [[ "${KERNEL_ONLY}" != "yes" ]]; then
 		display_alert "Building image" "${BOARD}" "target-started"
-		[[ $BSP_BUILD != yes ]] && build_rootfs_and_image # old debootstrap-ng. !!!LOGGING!!! handled inside, there are many sub-parts.
+		build_rootfs_and_image # old "debootstrap-ng"; has its own logging sections.
 		display_alert "Done building image" "${BOARD}" "target-reached"
 	fi
 
-	call_extension_method "run_after_build" <<- 'RUN_AFTER_BUILD'
-		*hook for function to run after build, i.e. to change owner of `$SRC`*
-		Really one of the last hooks ever called. The build has ended. Congratulations.
-		- *NOTE:* this will run only if there were no errors during build process.
-	RUN_AFTER_BUILD
-
-	end=$(date +%s)
-	runtime=$(((end - start) / 60))
-	# display_alert in its own logging section.
-	LOG_SECTION="runtime_total" do_with_logging display_alert "Runtime" "$runtime min" "info"
+	main_default_end_build
 
 	if armbian_is_running_in_container; then
-		BUILD_CONFIG='docker' # @TODO: this is not true, depends on how we end up launching this.
+		BUILD_CONFIG='docker' # @TODO: this is not true, CLI handles this differently, gotta ask the CLI; this whole thing is inconsistent
 	fi
 
 	# Make it easy to repeat build by displaying build options used. Prepare array. @TODO this is inconsistent. Maybe something like the relaunch vars?
@@ -230,20 +31,4 @@ function main_default_build_single() {
 	[[ -n ${DESKTOP_APT_FLAGS_SELECTED} ]] && repeat_args+=("DESKTOP_APT_FLAGS_SELECTED=\"${DESKTOP_APT_FLAGS_SELECTED}\"")
 	[[ -n ${COMPRESS_OUTPUTIMAGE} ]] && repeat_args+=("COMPRESS_OUTPUTIMAGE=${COMPRESS_OUTPUTIMAGE}")
 	display_alert "Repeat Build Options" "${repeat_args[*]}" "ext" # * = expand array, space delimited, single-word.
-
-}
-
-function trap_handler_cleanup_workdir() {
-	display_alert "Cleanup WORKDIR: $WORKDIR" "trap_handler_cleanup_workdir" "cleanup"
-	unset TMPDIR
-	if [[ -d "${WORKDIR}" ]]; then
-		if [[ "${PRESERVE_WORKDIR}" != "yes" ]]; then
-			display_alert "Cleaning up WORKDIR" "$(du -h -s "$WORKDIR")" "cleanup"
-			# Remove all files and directories in WORKDIR, but not WORKDIR itself.
-			rm -rf "${WORKDIR:?}"/* # Note this is protected by :?
-		else
-			display_alert "Preserving WORKDIR due to PRESERVE_WORKDIR=yes" "$(du -h -s "$WORKDIR")" "warn"
-			# @TODO: tmpfs might just be unmounted, though.
-		fi
-	fi
 }
diff --git a/lib/functions/main/start-end.sh b/lib/functions/main/start-end.sh
new file mode 100644
index 000000000..161f11c1d
--- /dev/null
+++ b/lib/functions/main/start-end.sh
@@ -0,0 +1,84 @@
+# Common start/end build functions. Used by main_default_build_single()
+
+function main_default_start_build() {
+	wait_for_disk_sync "before starting build" # fsync, wait for disk to sync, and then continue. alert user if takes too long.
+
+	# Check that WORKDIR_BASE_TMP exists; if not, create it.
+	if [[ ! -d "${WORKDIR_BASE_TMP}" ]]; then
+		mkdir -p "${WORKDIR_BASE_TMP}"
+	fi
+
+	# Check the sanity of WORKDIR_BASE_TMP regarding mount options.
+	LOG_SECTION="check_dir_for_mount_options" do_with_logging check_dir_for_mount_options "${WORKDIR_BASE_TMP}" "main temporary dir"
+
+	# Starting work. Export TMPDIR, which will be picked up by all `mktemp` invocations hopefully.
+	# Runner functions in logging/runners.sh will explicitly unset TMPDIR before invoking chroot.
+	# Invoking chroot directly will fail in subtle ways, so, please use the runner.sh functions.
+	display_alert "Starting single build, exporting TMPDIR" "${WORKDIR}" "debug"
+	LOG_SECTION="prepare_tmpfs_workdir" do_with_logging prepare_tmpfs_for "WORKDIR" "${WORKDIR}" # this adds its own cleanup handler, which deletes it if it was created
+	add_cleanup_handler trap_handler_cleanup_workdir                                             # this is for when it is NOT a tmpfs, for any reason; it does not delete the dir itself.
+
+	# 'declare -g -x': global, export
+	declare -g -x TMPDIR="${WORKDIR}"                    # TMPDIR is default for a lot of stuff, but...
+	declare -g -x CCACHE_TEMPDIR="${WORKDIR}/ccache_tmp" # Export CCACHE_TEMPDIR, under Workdir, which is hopefully under tmpfs. Thanks @the-Going for this.
+	declare -g -x XDG_RUNTIME_DIR="${WORKDIR}/xdg_tmp"   # XDG_RUNTIME_DIR is used by the likes of systemd/freedesktop centric apps.
+
+	declare -g start_timestamp # global timestamp; read below by main_default_end_build()
+	start_timestamp=$(date +%s)
+
+	### Write config summary
+	LOG_SECTION="config_summary" do_with_logging write_config_summary_output_file
+
+	# Check and install dependencies, directory structure and settings
+	prepare_host # this has its own logging sections, and is possibly interactive.
+
+	# Aggregate packages, in its own logging section; this decides internally on KERNEL_ONLY=no
+	# We need aggregation to be able to build bsp packages, which contain scripts coming from the aggregation.
+	LOG_SECTION="aggregate_packages" do_with_logging aggregate_packages
+
+	# Create a directory inside WORKDIR with a "python" symlink to "/usr/bin/python2"; add it to PATH first.
+	BIN_WORK_DIR="${WORKDIR}/bin"
+	# No cleanup of this is necessary, since it's inside WORKDIR.
+	mkdir -p "${BIN_WORK_DIR}"
+	ln -s "/usr/bin/python2" "${BIN_WORK_DIR}/python"
+	export PATH="${BIN_WORK_DIR}:${PATH}"
+
+	if [[ "${JUST_INIT}" == "yes" ]]; then
+		exit 0 # @TODO: is this used? if not, remove
+	fi
+
+}
+
+function main_default_end_build() {
+	call_extension_method "run_after_build" <<- 'RUN_AFTER_BUILD'
+		*hook for function to run after build, i.e. to change owner of `$SRC`*
+		Really one of the last hooks ever called. The build has ended. Congratulations.
+		- *NOTE:* this will run only if there were no errors during build process.
+	RUN_AFTER_BUILD
+
+	declare end_timestamp
+	end_timestamp=$(date +%s)
+	declare runtime=$(((end_timestamp - start_timestamp) / 60))
+	# display_alert in its own logging section.
+	LOG_SECTION="runtime_total" do_with_logging display_alert "Runtime" "${runtime} min" "info"
+
+	return 0
+}
+
+
+function trap_handler_cleanup_workdir() {
+	display_alert "Cleanup WORKDIR: $WORKDIR" "trap_handler_cleanup_workdir" "cleanup"
+	unset TMPDIR
+	if [[ -d "${WORKDIR}" ]]; then
+		if [[ "${PRESERVE_WORKDIR}" != "yes" ]]; then
+			if [[ "${SHOW_DEBUG}" == "yes" ]]; then
+				display_alert "Cleaning up WORKDIR" "$(du -h -s "$WORKDIR")" "cleanup"
+			fi
+			# Remove all files and directories in WORKDIR, but not WORKDIR itself.
+			rm -rf "${WORKDIR:?}"/* # Note this is protected by :?
+		else
+			display_alert "Preserving WORKDIR due to PRESERVE_WORKDIR=yes" "$(du -h -s "$WORKDIR")" "warn"
+			# @TODO: tmpfs might just be unmounted, though.
+		fi
+	fi
+}