diff --git a/lib/functions/cli/cli-patch.sh b/lib/functions/cli/cli-patch.sh
index 2cf57b38e..e461a43d4 100644
--- a/lib/functions/cli/cli-patch.sh
+++ b/lib/functions/cli/cli-patch.sh
@@ -34,7 +34,7 @@ function cli_patch_kernel_run() {
 		"kernel-${LINUXFAMILY}-${KERNEL_MAJOR_MINOR}:${target_branch}")
 
 	# Prepare the host and build kernel instead of main_default_build_single
-	LOG_SECTION="prepare_host" do_with_logging prepare_host
+	prepare_host # This handles its own logging sections, and is possibly interactive.
 	compile_kernel # This handles its own logging sections.
 
 	display_alert "Done patching kernel" "${BRANCH} - ${LINUXFAMILY} - ${KERNEL_MAJOR_MINOR}" "cachehit"
diff --git a/lib/functions/general/cleaning.sh b/lib/functions/general/cleaning.sh
index 2a812ebe5..2b2ae6fc9 100644
--- a/lib/functions/general/cleaning.sh
+++ b/lib/functions/general/cleaning.sh
@@ -86,3 +86,21 @@ function general_cleaning() {
 
 	return 0 # a LOT of shortcircuits above; prevent spurious error messages
 }
+
+function clean_deprecated_mountpoints() {
+	# Cleaning of old, deprecated mountpoints; only done if not running under Docker.
+	# mountpoints under Docker manifest as volumes, and as such can't be cleaned this way.
+	if [[ "${ARMBIAN_RUNNING_IN_CONTAINER}" != "yes" ]]; then
+		prepare_armbian_mountpoints_description_dict
+		local mountpoint=""
+		for mountpoint in "${ARMBIAN_MOUNTPOINTS_DEPRECATED[@]}"; do
+			local mountpoint_dir="${SRC}/${mountpoint}"
+			display_alert "Considering cleaning deprecated mountpoint" "${mountpoint_dir}" "debug"
+			if [[ -d "${mountpoint_dir}" ]]; then
+				display_alert "Cleaning deprecated mountpoint" "${mountpoint_dir}" "info"
+				run_host_command_logged rm -rf "${mountpoint_dir}"
+			fi
+		done
+	fi
+	return 0
+}
diff --git a/lib/functions/host/host-utils.sh b/lib/functions/host/host-utils.sh
index 26b1ec5af..56e41ae25 100644
--- a/lib/functions/host/host-utils.sh
+++ b/lib/functions/host/host-utils.sh
@@ -204,7 +204,7 @@ function mkdir_recursive_and_set_uid_owner() {
 	done
 }
 
-# Call: reset_uid_owner "one/file" "some/directory" "another/file"
+# Call: reset_uid_owner "one/file" "some/directory" "another/file" - is recursive if dir given
 function reset_uid_owner() {
 	if [[ "x${SET_OWNER_TO_UID}x" == "xx" ]]; then
 		return 0 # Nothing to do.
@@ -225,6 +225,26 @@ function reset_uid_owner() {
 	done
 }
 
+# Non recursive version of the above
+function reset_uid_owner_non_recursive() {
+	if [[ "x${SET_OWNER_TO_UID}x" == "xx" ]]; then
+		return 0 # Nothing to do.
+	fi
+	# Loop over args..
+	local arg
+	for arg in "$@"; do
+		display_alert "reset_uid_owner_non_recursive: '${arg}' will be owner id '${SET_OWNER_TO_UID}'" "reset_uid_owner_non_recursive" "debug"
+		if [[ -d "${arg}" ]]; then
+			chown "${SET_OWNER_TO_UID}" "${arg}"
+		elif [[ -f "${arg}" ]]; then
+			chown "${SET_OWNER_TO_UID}" "${arg}"
+		else
+			display_alert "reset_uid_owner_non_recursive: '${arg}' is not a file or directory" "skipping" "debug"
+			return 1
+		fi
+	done
+}
+
 # call: check_dir_for_mount_options "/path/to/dir" "main build dir description"
 function check_dir_for_mount_options() {
 	declare -r dir="${1}"
@@ -248,6 +268,7 @@ function check_dir_for_mount_options() {
 function trap_handler_reset_output_owner() {
 	display_alert "Resetting output directory owner" "${SRC}/output" "debug"
 	reset_uid_owner "${SRC}/output"
+	# For .tmp: do NOT do it recursively. If another build is running in another process, this is destructive if recursive.
 	display_alert "Resetting tmp directory owner" "${SRC}/.tmp" "debug"
-	reset_uid_owner "${SRC}/.tmp"
+	reset_uid_owner_non_recursive "${SRC}/.tmp"
 }
diff --git a/lib/functions/host/prepare-host.sh b/lib/functions/host/prepare-host.sh
index 468fb28ec..b3ba7d1b1 100644
--- a/lib/functions/host/prepare-host.sh
+++ b/lib/functions/host/prepare-host.sh
@@ -5,19 +5,26 @@
 # * creates directory structure
 # * changes system settings
 #
-prepare_host() {
+function prepare_host() {
+	# Those are not logged, and might be interactive.
+	display_alert "Checking" "host" "info"
+	obtain_and_check_host_release_and_arch # sets HOSTRELEASE and validates it for sanity; also HOSTARCH
+	check_host_has_enough_disk_space       # Checks disk space and exits if not enough
+	wait_for_package_manager               # wait until dpkg is not locked...
+
+	LOG_SECTION="prepare_host_noninteractive" do_with_logging prepare_host_noninteractive
+	return 0
+}
+
+function prepare_host_noninteractive() {
 	display_alert "Preparing" "host" "info"
 
 	# The 'offline' variable must always be set to 'true' or 'false'
+	declare offline=false
 	if [ "$OFFLINE_WORK" == "yes" ]; then
-		local offline=true
-	else
-		local offline=false
+		offline=true
 	fi
 
-	# wait until package manager finishes possible system maintanace
-	wait_for_package_manager
-
 	# fix for Locales settings, if locale-gen is installed, and /etc/locale.gen exists.
 	if [[ -n "$(command -v locale-gen)" && -f /etc/locale.gen ]]; then
 		if ! grep -q "^en_US.UTF-8 UTF-8" /etc/locale.gen; then
@@ -53,16 +60,6 @@ prepare_host() {
 		done
 	fi
 
-	obtain_and_check_host_release_and_arch # sets HOSTRELEASE and validates it for sanity; also HOSTARCH
-
-	if grep -qE "(Microsoft|WSL)" /proc/version; then
-		if [ -f /.dockerenv ]; then
-			display_alert "Building images using Docker on WSL2 may fail" "" "wrn"
-		else
-			exit_with_error "Windows subsystem for Linux is not a supported build environment"
-		fi
-	fi
-
 	declare -g USE_LOCAL_APT_DEB_CACHE=${USE_LOCAL_APT_DEB_CACHE:-yes} # Use SRC/cache/aptcache as local apt cache by default
 	display_alert "Using local apt cache?" "USE_LOCAL_APT_DEB_CACHE: ${USE_LOCAL_APT_DEB_CACHE}" "debug"
 
@@ -111,12 +108,11 @@ prepare_host() {
 	mkdir -p "${SRC}"/{cache,output} "${USERPATCHES_PATH}"
 
 	# @TODO: original: mkdir -p "${DEST}"/debs-beta/extra "${DEST}"/debs/extra "${DEST}"/{config,debug,patch} "${USERPATCHES_PATH}"/overlay "${SRC}"/cache/{sources,hash,hash-beta,toolchain,utility,rootfs} "${SRC}"/.tmp
-	mkdir -p "${USERPATCHES_PATH}"/overlay "${SRC}"/cache/{sources,hash,hash-beta,toolchain,utility,rootfs} "${SRC}"/.tmp
+	mkdir -p "${USERPATCHES_PATH}"/overlay "${SRC}"/cache/{sources,rootfs} "${SRC}"/.tmp
 
 	# If offline, do not try to download/install toolchains.
 	if ! $offline; then
-		# Mostly deprecated.
-		download_external_toolchains
+		download_external_toolchains # Mostly deprecated, since SKIP_EXTERNAL_TOOLCHAINS=yes is the default
 	fi
 
 	# if we're building an image, not only packages...
@@ -163,18 +159,15 @@ prepare_host() {
 				test -e /proc/sys/fs/binfmt_misc/qemu-arm || update-binfmts --enable qemu-arm
 				test -e /proc/sys/fs/binfmt_misc/qemu-aarch64 || update-binfmts --enable qemu-aarch64
 			fi
+
+			# @TODO: we could create a tiny loop here to test if the binfmt_misc is working, but this is before deps are installed.
 		fi
 	fi
 
 	# @TODO: rpardini: this does not belong here, instead with the other templates, pre-configuration.
 	[[ ! -f "${USERPATCHES_PATH}"/customize-image.sh ]] && run_host_command_logged cp -pv "${SRC}"/config/templates/customize-image.sh.template "${USERPATCHES_PATH}"/customize-image.sh
 
-	# @TODO: what is this, and why?
-	if [[ ! -f "${USERPATCHES_PATH}"/README ]]; then
-		rm -f "${USERPATCHES_PATH}"/readme.txt
-		echo 'Please read documentation about customizing build configuration' > "${USERPATCHES_PATH}"/README
-		echo 'https://www.armbian.com/using-armbian-tools/' >> "${USERPATCHES_PATH}"/README
-
+	if [[ -d "${USERPATCHES_PATH}" ]]; then
 		# create patches directory structure under USERPATCHES_PATH
 		find "${SRC}"/patch -maxdepth 2 -type d ! -name . | sed "s%/.*patch%/$USERPATCHES_PATH%" | xargs mkdir -p
 	fi
@@ -182,16 +175,7 @@ prepare_host() {
 	# Reset owner of userpatches if so required
 	reset_uid_owner "${USERPATCHES_PATH}" # Fix owner of files in the final destination
 
-	# @TODO: check every possible mount point. Not only one. People might have different mounts / Docker volumes...
-	# check free space (basic) @TODO probably useful to refactor and implement in multiple spots.
-	declare -i free_space_bytes
-	free_space_bytes=$(findmnt --noheadings --output AVAIL --bytes --target "${SRC}" --uniq 2> /dev/null) # in bytes
-	if [[ -n "$free_space_bytes" && $((free_space_bytes / 1073741824)) -lt 10 ]]; then
-		display_alert "Low free space left" "$((free_space_bytes / 1073741824)) GiB" "wrn"
-		# pause here since dialog-based menu will hide this message otherwise
-		echo -e "Press \e[0;33m<Ctrl-C>\x1B[0m to abort compilation, \e[0;33m<Enter>\x1B[0m to ignore and continue"
-		read # @TODO: this fails if stdin is not a tty, or just hangs
-	fi
+	return 0
 }
 
 # Early: we've possibly no idea what the host release or arch we're building on, or what the target arch is. All-deps.
@@ -356,3 +340,14 @@ function install_host_dependencies() {
 
 	unset FINAL_HOST_DEPS # don't leak this after the hook is done
 }
+
+function check_host_has_enough_disk_space() {
+	# @TODO: check every possible mount point. Not only one. People might have different mounts / Docker volumes...
+	# check free space (basic) @TODO probably useful to refactor and implement in multiple spots.
+	declare -i free_space_bytes
+	free_space_bytes=$(findmnt --noheadings --output AVAIL --bytes --target "${SRC}" --uniq 2> /dev/null) # in bytes
+	if [[ -n "$free_space_bytes" && $((free_space_bytes / 1073741824)) -lt 10 ]]; then
+		display_alert "Low free space left" "$((free_space_bytes / 1073741824))GiB" "wrn"
+		exit_if_countdown_not_aborted 10 "Low free disk space left" # This pauses & exits if error if ENTER is not pressed in 10 seconds
+	fi
+}
diff --git a/lib/functions/logging/traps.sh b/lib/functions/logging/traps.sh
index 5f52850a1..dbf768788 100644
--- a/lib/functions/logging/traps.sh
+++ b/lib/functions/logging/traps.sh
@@ -165,3 +165,35 @@ function exit_with_error() {
 
 	exit 43
 }
+
+# This exits, unless user presses ENTER. If not interactive, user will be unable to comply and the script will exit.
+function exit_if_countdown_not_aborted() {
+	# parse
+	declare -i loops="${1}"
+	declare reason="${2}"
+	# validate
+	[[ -z "${loops}" ]] && exit_with_error "countdown_to_exit_or_just_exit_if_noninteractive() called without a number of loops"
+	[[ -z "${reason}" ]] && exit_with_error "countdown_to_exit_or_just_exit_if_noninteractive() called without a reason"
+
+	# If not interactive, just exit.
+	if [[ ! -t 1 ]]; then
+		exit_with_error "Exiting due to '${reason}' - not interactive, exiting immediately."
+	fi
+
+	display_alert "Problem detected" "${reason}" "err"
+	display_alert "Exiting in ${loops} seconds" "Press \e[0;33m<Ctrl-C>\x1B[0m to abort, \e[0;33m<Enter>\x1B[0m to ignore and continue" "err"
+	echo -n "Counting down: "
+	for i in $(seq 1 "${loops}"); do
+		declare stop_waiting=0
+		declare keep_waiting=0
+		timeout --foreground 1 bash -c "read -n1; echo \$REPLY" && stop_waiting=1 || keep_waiting=1
+		if [[ "$stop_waiting" == "1" ]]; then
+			display_alert "User pressed ENTER, continuing, albeit" "${reason}" "wrn"
+			return 0
+		fi
+		echo -n "$i... " >&2
+	done
+
+	# Countdown finished, exit.
+	exit_with_error "Exiting due to '${reason}'"
+}
diff --git a/lib/functions/main/default-build.sh b/lib/functions/main/default-build.sh
index 8a6ea0065..e477629b4 100644
--- a/lib/functions/main/default-build.sh
+++ b/lib/functions/main/default-build.sh
@@ -16,18 +16,18 @@ function main_default_build_single() {
 	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.
 
-	# '-x': export
+	# '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.
 
-	start=$(date +%s)
+	declare start=$(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
-	LOG_SECTION="prepare_host" do_with_logging prepare_host
+	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
@@ -44,7 +44,8 @@ function main_default_build_single() {
 	fi
 
 	if [[ $CLEAN_LEVEL == *sources* ]]; then
-		general_cleaning "sources"
+		# 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.
@@ -72,20 +73,7 @@ function main_default_build_single() {
 			LOG_SECTION="fetch_and_build_host_tools" do_with_logging fetch_and_build_host_tools
 		fi
 
-		# Cleaning of old, deprecated mountpoints; only done if not running under Docker.
-		# mountpoints under Docker manifest as volumes, and as such can't be cleaned this way.
-		if [[ "${ARMBIAN_RUNNING_IN_CONTAINER}" != "yes" ]]; then
-			prepare_armbian_mountpoints_description_dict
-			local mountpoint=""
-			for mountpoint in "${ARMBIAN_MOUNTPOINTS_DEPRECATED[@]}"; do
-				local mountpoint_dir="${SRC}/${mountpoint}"
-				display_alert "Considering cleaning deprecated mountpoint" "${mountpoint_dir}" "debug"
-				if [[ -d "${mountpoint_dir}" ]]; then
-					display_alert "Cleaning deprecated mountpoint" "${mountpoint_dir}" "info"
-					run_host_command_logged rm -rf "${mountpoint_dir}"
-				fi
-			done
-		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
@@ -95,7 +83,7 @@ function main_default_build_single() {
 	fi
 
 	# Prepare ccache, cthreads, etc for the build
-	prepare_compilation_vars
+	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'.
@@ -223,13 +211,14 @@ function main_default_build_single() {
 
 	end=$(date +%s)
 	runtime=$(((end - start) / 60))
-	display_alert "Runtime" "$runtime min" "info"
+	# display_alert in its own logging section.
+	LOG_SECTION="runtime_total" do_with_logging display_alert "Runtime" "$runtime min" "info"
 
 	if armbian_is_running_in_container; then
 		BUILD_CONFIG='docker' # @TODO: this is not true, depends on how we end up launching this.
 	fi
 
-	# Make it easy to repeat build by displaying build options used. Prepare array.
+	# Make it easy to repeat build by displaying build options used. Prepare array. @TODO this is inconsistent. Maybe something like the relaunch vars?
 	local -a repeat_args=("./compile.sh" "${BUILD_CONFIG}" " BRANCH=${BRANCH}")
 	[[ -n ${RELEASE} ]] && repeat_args+=("RELEASE=${RELEASE}")
 	[[ -n ${BUILD_MINIMAL} ]] && repeat_args+=("BUILD_MINIMAL=${BUILD_MINIMAL}")