Optionally symlink files from persistent source instead of mount it.

This is done by passing the option "linkfiles" to a live.persist
entry. That option is very useful when you only want certain files
to be persistent, not the whole directory they are in, like dot-files
in $home.

scripts/live

@@ -1596,15 +1596,21 @@ setup_unionfs ()
 	# Adding other custom mounts
 	if [ -n "${PERSISTENT}" ] && [ -z "${NOPERSISTENT}" ]
 	then
-		bindings="/${persistence_list}"
-		touch ${bindings}
+		bindings="/bindings.list"
+		links="/links.list"
+		custom_mounts="/custom_mounts.list"
+		rm -f ${bindings} ${links} ${custom_mounts} >/dev/null 2>&1
+		persistent_backing="${rootmnt}/live/persistent"
+
+		# First we scan all media and gather all information about custom mounts
 		for device in ${overlay_devices}
 		do
 			if [ ! -b "${device}" ]
 			then
 				continue
 			fi
-			backing="/$(basename ${device})-backing"
+			device_name="$(basename ${device})"
+			backing="${persistent_backing}/${device_name}"
 			mkdir -p "${backing}"
 			device_fstype="$(get_fstype ${device})"
 			if [ -z "${PERSISTENT_READONLY}" ]
@@ -1623,34 +1629,56 @@ setup_unionfs ()
 				continue
 			fi
 
-			# FIXME: debug stuff, remove me?
-			[ "${DEBUG}" = "Yes" ] && cat ${include_list} >> ${rootmnt}/${bindings}-origs
-			while read source dest
+			[ "${DEBUG}" = "Yes" ] && cp ${include_list} ${persistent_backing}/${persistence_list}.${device_name}
+			while read source dest options # < ${include_list}
 			do
 				if echo ${source} | grep -qe "^[[:space:]]*#"
 				then
 					# skipping commented line
 					continue
 				fi
-				if [ -z "${dest}" ]
+
+				if echo ${dest} | grep -qe "^[^/]"
+				then
+					options="${dest}"
+					dest="${source}"
+				elif [ -z "${dest}" ]
 				then
 					dest="${source}"
 				fi
+
 				if echo ${dest} | grep -qe "^/\+$\|^/\+live\(/.*\)\?$"
 				then
 					# mounting on / or /live could cause trouble
 					log_warning_msg "Skipping unsafe custom mount on ${dest}"
 					continue
 				fi
 
-				# FIXME: handle case: we already have /a/b in $bindings, but now we find /a -- /a should replace /a/b in $bindings.
-				# FIXME: handle case: we have /a in $bindings, now we find /a/b, so we skip /a/b
+				for opt in $(echo ${options} | tr ',' ' ');
+				do
+					case "${opt}" in
+						"linkfiles")
+							;;
+						*)
+							log_warning_msg "Skipping custom mount with unkown option: ${opt}"
+							continue
+							;;
+					esac
+				done
+
+				# FIXME: handle case: we already have /a/b in $bindings added from current $device, but now we find /a -- /a should replace /a/b in $bindings.
+				# FIXME: handle case: we have /a in $bindings from current $device, now we find /a/b, so we skip /a/b
 
 				# ensure that no multiple-/ occur in paths
 				full_source="$(echo ${backing}/${source}/ | sed -e 's|/\+|/|g')"
 				full_dest="$(echo ${rootmnt}/${dest}/ | sed -e 's|/\+|/|g')"
 				device_used="yes"
-				echo "${full_source} ${full_dest}" >> ${bindings}
+				if echo ${options} | grep -qe "\<linkfiles\>";
+				then
+					echo "${full_source} ${full_dest} ${options}" >> ${links}
+				else
+					echo "${full_source} ${full_dest} ${options}" >> ${bindings}
+				fi
 			done < ${include_list}
 
 			if [ -z "${device_used}" ]
@@ -1661,13 +1689,19 @@ setup_unionfs ()
 			fi
 		done
 
-		# we sort the list according to destination so we're sure that we won't hide a previous mount. we also ignore duplicate destinations in a more or less arbitrary way
-		sort -k2 -sbu ${bindings} -o ${bindings}
+		# We sort the list according to destination so we're sure 
+		# that we won't hide a previous mount. We also  ignore
+		# duplicate destinations in a more or less arbitrary way.
+		[ -e "${bindings}" ] && sort -k2 -sbu ${bindings} >> ${custom_mounts}
+
+		# After all mounts are considered we add symlinks so they
+		# won't be hidden by some mount.
+		[ -e "${links}" ] && sort -k2 -sbu ${links} >> ${custom_mounts}
 
-		# FIXME: debug stuff, remove me?
-		[ "${DEBUG}" = "Yes" ] && cp ${bindings} ${rootmnt}/${bindings}-results
+		[ "${DEBUG}" = "Yes" ] && cp ${custom_mounts} ${persistent_backing}
 
-		while read source dest
+		# Now we do the actual mounting (and symlinking)
+		while read source dest options	# < ${custom_mounts}
 		do
 			if mountpoint -q "${dest}";
 			then
@@ -1707,7 +1741,7 @@ setup_unionfs ()
 			# dealing with /etc or other system dir.
 			if [ ! -d "${source}" ]
 			then
-				if [ -n "${PERSISTENT_READONLY}" ]
+				if [ -n "${PERSISTENT_READONLY}" ] || echo ${options} | grep -qe "\<linkfiles\>"
 				then
 					continue
 				fi
@@ -1718,14 +1752,31 @@ setup_unionfs ()
 
 			if [ -z "${PERSISTENT_READONLY}" ]
 			then
-				mount --bind "${source}" "${dest}"
+				if echo ${options} | grep -qe "\<linkfiles\>";
+				then
+					links_source="${source}"
+					links_dest="${dest}"
+				else
+					mount --bind "${source}" "${dest}"
+				fi
 			else
+				if echo ${options} | grep -qe "\<linkfiles\>";
+				then
+					links_dest="${dest}"
+					dest="$(mktemp -d ${persistent_backing}/links_source-XXXXXX)"
+					links_source="${dest}"
+				fi
 				unionrw="$(echo ${dest} | sed -e "s|${rootmnt}|/cow/|")"
 				mkdir -p ${unionrw}
 				unionmountopts="noatime,${noxino_opt}dirs=${unionrw}=rw:${source}=${roopt}"
 				mount -t "${UNIONTYPE}" -o "${unionmountopts}" "${UNIONTYPE}" "${dest}"
 			fi
-		done < ${bindings}
+
+			if echo $options | grep -qe "\<linkfiles\>";
+			then
+				link_files "${links_source}" "${links_dest}" "${rootmnt}"
+			fi
+		done < ${custom_mounts}
 		rm -f ${bindings}
 
 		# Look for other snapshots to copy in

scripts/live-helpers

@@ -556,3 +556,55 @@ non_removable_dev ()
 
 	echo "${ret}"
 }
+
+link_files ()
+{
+	# create source's directory structure in dest, and recursively
+	# create symlinks in dest to to all files in source. if mask
+	# is non-empty, remove mask from all source paths when
+	# creating links (will be necessary if we change root, which
+	# live-boot normally does (into $rootmnt)).
+
+	# remove multiple /:s and ensure ending on /
+	local src_dir="$(echo "${1}"/ | sed -e 's|/\+|/|g')"
+	local dest_dir="$(echo "${2}"/ | sed -e 's|/\+|/|g')"
+	local src_mask="${3}"
+
+	# This check can only trigger on the inital, non-recursive call since
+	# we create the destination before recursive calls
+	if [ ! -d "${dest_dir}" ];
+	then
+		log_warning_msg "Must link_files into a directory"
+		return
+	fi
+
+	find "${src_dir}" -mindepth 1 -maxdepth 1 | while read x; do
+		local src="${x}"
+		local dest="${dest_dir}$(basename "${x}")"
+		if [ -d "${src}" ];
+		then
+			if [ -z "$(ls -A "${src}")" ];
+			then
+				continue
+			fi
+			if [ ! -d "${dest}" ];
+			then
+				mkdir -p "${dest}"
+				prev="$(dirname "${dest}")"
+				chown $(stat -c %u:%g "${prev}") "${dest}"
+				chmod $(stat -c %a "${prev}") "${dest}"
+			fi
+			link_files "${src}" "${dest}" "${src_mask}"
+		else
+			if [ -e "${dest}" ];
+			then
+				rm -rf "${dest}"
+			fi
+			if [ -n "${src}" ];
+			then
+				src="$(echo ${src} | sed "s|^${src_mask}||")"
+			fi
+			ln -s "${src}" "${dest}"
+		fi
+	done
+}