Readonly rootfs support

index 3c9dea9..709cdf6 100644
@@ -23,3 +23,7 @@ FSCKFIX=yes
 #TICKADJ=10000
 # Enable caching in populate-volatile.sh
 VOLATILE_ENABLE_CACHE=yes
+# Indicate whether the rootfs is intended to be read-only or not.
+# Setting ROOTFS_READ_ONLY to yes and rebooting will give you a read-only rootfs.
+# Normally you should not change this value.
+ROOTFS_READ_ONLY=no

index de073b8..bf6a29b 100644
@@ -5,7 +5,7 @@ SECTION = "base"
 LICENSE = "GPLv2+"
 LIC_FILES_CHKSUM = "file://COPYING;md5=751419260aa954499f7abaabaa882bbe \
                     file://COPYRIGHT;endline=15;md5=349c872e0066155e1818b786938876a4"
-PR = "r9"
+PR = "r10"
 
 RDEPENDS_${PN} = "${PN}-inittab"
 

index 9b4dec8..9c51bf6 100644
@@ -201,6 +201,24 @@ run_intercept_scriptlets () {
 	fi
 }
 
+# A hook function to support read-only-rootfs IMAGE_FEATURES
+# Currently, it only supports sysvinit system.
+read_only_rootfs_hook () {
+	if ${@base_contains("DISTRO_FEATURES", "sysvinit", "true", "false", d)}; then
+	        # Tweak the mount option in fstab
+		sed -i '/rootfs/ s/defaults/ro/' ${IMAGE_ROOTFS}/etc/fstab
+	        # Change the value of ROOTFS_READ_ONLY in /etc/default/rcS to yes
+		if [ -e ${IMAGE_ROOTFS}/etc/default/rcS ]; then
+			sed -i 's/ROOTFS_READ_ONLY=no/ROOTFS_READ_ONLY=yes/' ${IMAGE_ROOTFS}/etc/default/rcS
+		fi
+	        # Run populate-volatile.sh at rootfs time to set up basic files
+	        # and directories to support read-only rootfs.
+		if [ -e ${IMAGE_ROOTFS}/etc/init.d/populate-volatile.sh ]; then
+			${IMAGE_ROOTFS}/etc/init.d/populate-volatile.sh
+		fi
+	fi
+}
+
 fakeroot do_rootfs () {
 	#set -x
 	# When use the rpm incremental image generation, don't remove the rootfs

index 657d5f2..4c70d32 100644
@@ -29,6 +29,7 @@ LIC_FILES_CHKSUM = "file://${COREBASE}/LICENSE;md5=3f40d7994397109285ec7b81fdeb3
 # - dev-pkgs            - development packages (headers, etc.) for all installed packages in the rootfs
 # - dbg-pkgs            - debug symbol packages for all installed packages in the rootfs
 # - doc-pkgs            - documentation packages for all installed packages in the rootfs
+# - read-only-rootfs    - tweaks an image to support read-only rootfs
 #
 PACKAGE_GROUP_x11 = "packagegroup-core-x11"
 PACKAGE_GROUP_x11-base = "packagegroup-core-x11-base"

@@ -80,3 +81,6 @@ ROOTFS_POSTPROCESS_COMMAND += "rootfs_update_timestamp ; "
 
 # Zap the root password if debug-tweaks feature is not enabled
 ROOTFS_POSTPROCESS_COMMAND += '${@base_contains("IMAGE_FEATURES", "debug-tweaks", "", "zap_root_password ; ",d)}'
+
+# Tweak the mount options for rootfs in /etc/fstab if read-only-rootfs is enabled
+ROOTFS_POSTPROCESS_COMMAND += '${@base_contains("IMAGE_FEATURES", "read-only-rootfs", "read_only_rootfs_hook; ", "",d)}'

index d2175d7..61ef6c9 100755
@@ -8,192 +8,191 @@
 # Short-Description:  Populate the volatile filesystem
 ### END INIT INFO
 
-. /etc/default/rcS
-
-CFGDIR="/etc/default/volatiles"
-TMPROOT="/var/tmp"
+# Get ROOT_DIR
+DIRNAME=`dirname $0`
+ROOT_DIR=`echo $DIRNAME | sed -ne 's:etc/.*::p'`
+
+. ${ROOT_DIR}/etc/default/rcS
+# When running populat-volatile.sh at rootfs time, disable cache.
+[ "$ROOT_DIR" != "/" ] && VOLATILE_ENABLE_CACHE=no
+# If rootfs is read-only, disable cache.
+[ "$ROOTFS_READ_ONLY" = "yes" ] && VOLATILE_ENABLE_CACHE=no
+# All above statements will be moved to a central place, say var.sh which
+# encapsulates '. /etc/default/rcS'.
+
+CFGDIR="${ROOT_DIR}/etc/default/volatiles"
+TMPROOT="${ROOT_DIR}/var/volatile/tmp"
 COREDEF="00_core"
+READONLY_MATCH="readonly-"
 
-[ "${VERBOSE}" != "no" ] && echo "Populating volatile Filesystems."
+[ "${VERBOSE}" != "no" ] && echo "Setting up basic files related to volatile storage under ${ROOT_DIR}."
 
 create_file() {
-	EXEC=" 
-	touch \"$1\"; 
-	chown ${TUSER}.${TGROUP} $1 || echo \"Failed to set owner -${TUSER}- for -$1-.\" >/dev/tty0 2>&1; 
-	chmod ${TMODE} $1 || echo \"Failed to set mode -${TMODE}- for -$1-.\" >/dev/tty0 2>&1 " 
+	EXEC="
+	touch \"$1\";
+	chown ${TUSER}.${TGROUP} $1 || echo \"Failed to set owner -${TUSER}- for -$1-.\" > /dev/null 2>&1;
+	chmod ${TMODE} $1 || echo \"Failed to set mode -${TMODE}- for -$1-.\" > /dev/null 2>&1 "
 
 	test "$VOLATILE_ENABLE_CACHE" = yes && echo "$EXEC" >> /etc/volatile.cache.build
 
 	[ -e "$1" ] && {
-	  [ "${VERBOSE}" != "no" ] && echo "Target already exists. Skipping."
+		[ "${VERBOSE}" != "no" ] && echo "Target $1 already exists. Skipping."
 	} || {
-	  eval $EXEC &
+		if [ "$ROOT_DIR" = "/" ]; then
+			eval $EXEC
+		else
+			# Some operations at rootfs time may fail and should fail,
+		        # but these failures should not be logged.
+			eval $EXEC > /dev/null 2>&1
+		fi
 	}
 }
 
 mk_dir() {
-	EXEC=" 
-	mkdir -p \"$1\"; 
-	chown ${TUSER}.${TGROUP} $1 || echo \"Failed to set owner -${TUSER}- for -$1-.\" >/dev/tty0 2>&1; 
-	chmod ${TMODE} $1 || echo \"Failed to set mode -${TMODE}- for -$1-.\" >/dev/tty0 2>&1 "
+	EXEC="
+	mkdir -p \"$1\";
+	chown ${TUSER}.${TGROUP} $1 || echo \"Failed to set owner -${TUSER}- for -$1-.\" 2>&1; 
+	chmod ${TMODE} $1 || echo \"Failed to set mode -${TMODE}- for -$1-.\" 2>&1 "
 
 	test "$VOLATILE_ENABLE_CACHE" = yes && echo "$EXEC" >> /etc/volatile.cache.build
-	
 	[ -e "$1" ] && {
-	  [ "${VERBOSE}" != "no" ] && echo "Target already exists. Skipping."
+		[ "${VERBOSE}" != "no" ] && echo "Target ${1} already exists. Skipping."
 	} || {
-	  eval $EXEC
+		if [ "$ROOT_DIR" = "/" ]; then
+			eval $EXEC
+		else
+			# Some operations at rootfs time may fail and should fail,
+                        # but these failures should not be logged.
+			eval $EXEC > /dev/null 2>&1
+		fi
 	}
 }
 
 link_file() {
-	EXEC="test -e \"$2\" -o -L $2 || ln -s \"$1\" \"$2\" >/dev/tty0 2>&1" 
-
-	test "$VOLATILE_ENABLE_CACHE" = yes && echo "	$EXEC" >> /etc/volatile.cache.build
-	
-	[ -e "$2" ] && {
-	  echo "Cannot create link over existing -${TNAME}-." >&2
-	} || {
-	  eval $EXEC &
-	}
+	EXEC="
+	if [ -L \"$2\" ]; then
+		[ \"$(readlink -f \"$2\")\" != \"$(readlink -f \"$1\")\" ] && { rm -f \"$2\"; ln -sf \"$1\" \"$2\"; };
+	elif [ -d \"$2\" ]; then
+		for f in $2/* $2/.[^.]*; do [ -e $f ] && cp -rf $f $1; done;
+		rm -rf \"$2\";
+		ln -sf \"$1\" \"$2\";
+	else
+		ln -sf \"$1\" \"$2\";
+	fi
+        "
+        test "$VOLATILE_ENABLE_CACHE" = yes && echo "   $EXEC" >> /etc/volatile.cache.build
+	if [ "$ROOT_DIR" = "/" ]; then
+		eval $EXEC
+	else
+		# Some operations at rootfs time may fail and should fail,
+                # but these failures should not be logged
+		eval $EXEC > /dev/null 2>&1
+	fi
 }
 
 check_requirements() {
+	cleanup() {
+		rm "${TMP_INTERMED}"
+		rm "${TMP_DEFINED}"
+		rm "${TMP_COMBINED}"
+	}
+	
+	CFGFILE="$1"
+	[ `basename "${CFGFILE}"` = "${COREDEF}" ] && return 0
+	# read-only-rootfs specific conf files should only be applied when rootfs is read-only
+	case `basename "${CFGFILE}"` in
+		${READONLY_MATCH}*)
+		[ "$ROOTFS_READ_ONLY" = "yes" ] && return 0 || return 1
+		;;
+		*)
+		;;
+	esac
 
-  cleanup() {
-    rm "${TMP_INTERMED}"
-    rm "${TMP_DEFINED}"
-    rm "${TMP_COMBINED}"
-    }
-    
-  CFGFILE="$1"
-
-  [ `basename "${CFGFILE}"` = "${COREDEF}" ] && return 0
-
-  TMP_INTERMED="${TMPROOT}/tmp.$$"
-  TMP_DEFINED="${TMPROOT}/tmpdefined.$$"
-  TMP_COMBINED="${TMPROOT}/tmpcombined.$$"
-
-
-  cat /etc/passwd | sed 's@\(^:\)*:.*@\1@' | sort | uniq > "${TMP_DEFINED}"
-  cat ${CFGFILE} | grep -v "^#" | cut -d " " -f 2 > "${TMP_INTERMED}"
-  cat "${TMP_DEFINED}" "${TMP_INTERMED}" | sort | uniq > "${TMP_COMBINED}"
-
-  NR_DEFINED_USERS="`cat "${TMP_DEFINED}" | wc -l`"
-  NR_COMBINED_USERS="`cat "${TMP_COMBINED}" | wc -l`"
-
-  [ "${NR_DEFINED_USERS}" -ne "${NR_COMBINED_USERS}" ] && {
-    echo "Undefined users:"
-    diff "${TMP_DEFINED}" "${TMP_COMBINED}" | grep "^>"
-    cleanup
-    return 1
-    }
-
+	TMP_INTERMED="${TMPROOT}/tmp.$$"
+	TMP_DEFINED="${TMPROOT}/tmpdefined.$$"
+	TMP_COMBINED="${TMPROOT}/tmpcombined.$$"
+
+	cat ${ROOT_DIR}/etc/passwd | sed 's@\(^:\)*:.*@\1@' | sort | uniq > "${TMP_DEFINED}"
+	cat ${CFGFILE} | grep -v "^#" | cut -d " " -f 2 > "${TMP_INTERMED}"
+	cat "${TMP_DEFINED}" "${TMP_INTERMED}" | sort | uniq > "${TMP_COMBINED}"
+	NR_DEFINED_USERS="`cat "${TMP_DEFINED}" | wc -l`"
+	NR_COMBINED_USERS="`cat "${TMP_COMBINED}" | wc -l`"
+
+	[ "${NR_DEFINED_USERS}" -ne "${NR_COMBINED_USERS}" ] && {
+		echo "Undefined users:"
+		diff "${TMP_DEFINED}" "${TMP_COMBINED}" | grep "^>"
+		cleanup
+		return 1
+	}
 
-  cat /etc/group | sed 's@\(^:\)*:.*@\1@' | sort | uniq > "${TMP_DEFINED}"
-  cat ${CFGFILE} | grep -v "^#" | cut -d " " -f 3 > "${TMP_INTERMED}"
-  cat "${TMP_DEFINED}" "${TMP_INTERMED}" | sort | uniq > "${TMP_COMBINED}"
 
-  NR_DEFINED_GROUPS="`cat "${TMP_DEFINED}" | wc -l`"
-  NR_COMBINED_GROUPS="`cat "${TMP_COMBINED}" | wc -l`"
+	cat ${ROOT_DIR}/etc/group | sed 's@\(^:\)*:.*@\1@' | sort | uniq > "${TMP_DEFINED}"
+	cat ${CFGFILE} | grep -v "^#" | cut -d " " -f 3 > "${TMP_INTERMED}"
+	cat "${TMP_DEFINED}" "${TMP_INTERMED}" | sort | uniq > "${TMP_COMBINED}"
 
-  [ "${NR_DEFINED_GROUPS}" -ne "${NR_COMBINED_GROUPS}" ] && {
-    echo "Undefined groups:"
-    diff "${TMP_DEFINED}" "${TMP_COMBINED}" | grep "^>"
-    cleanup
-    return 1
-    }
+	NR_DEFINED_GROUPS="`cat "${TMP_DEFINED}" | wc -l`"
+	NR_COMBINED_GROUPS="`cat "${TMP_COMBINED}" | wc -l`"
 
-  # Add checks for required directories here
+	[ "${NR_DEFINED_GROUPS}" -ne "${NR_COMBINED_GROUPS}" ] && {
+		echo "Undefined groups:"
+		diff "${TMP_DEFINED}" "${TMP_COMBINED}" | grep "^>"
+		cleanup
+		return 1
+	}
 
-  cleanup
-  return 0
-  }
+	cleanup
+	return 0
+}
 
 apply_cfgfile() {
+	CFGFILE="$1"
+	[ ${VERBOSE} != "no" ] && echo "Applying config file: $CFGFILE"
+	
+	check_requirements "${CFGFILE}" || {
+		echo "Skipping ${CFGFILE}"
+		return 1
+	}
 
-  CFGFILE="$1"
-
-  check_requirements "${CFGFILE}" || {
-    echo "Skipping ${CFGFILE}"
-    return 1
-    }
-
-  cat ${CFGFILE} | grep -v "^#" | \
-  while read LINE; do
-
-    eval `echo "$LINE" | sed -n "s/\(.*\)\ \(.*\) \(.*\)\ \(.*\)\ \(.*\)\ \(.*\)/TTYPE=\1 ; TUSER=\2; TGROUP=\3; TMODE=\4; TNAME=\5 TLTARGET=\6/p"`
-
-    [ "${VERBOSE}" != "no" ] && echo "Checking for -${TNAME}-."
-
-
-    [ "${TTYPE}" = "l" ] && {
-      TSOURCE="$TLTARGET"
-      [ -L "${TNAME}" ] || {
-        [ "${VERBOSE}" != "no" ] && echo "Creating link -${TNAME}- pointing to -${TSOURCE}-."
-        link_file "${TSOURCE}" "${TNAME}" &
-        }
-      continue
-      }
-
-    [ -L "${TNAME}" ] && {
-      [ "${VERBOSE}" != "no" ] && echo "Found link."
-      NEWNAME=`ls -l "${TNAME}" | sed -e 's/^.*-> \(.*\)$/\1/'`
-      echo ${NEWNAME} | grep -v "^/" >/dev/null && {
-        TNAME="`echo ${TNAME} | sed -e 's@\(.*\)/.*@\1@'`/${NEWNAME}"
-        [ "${VERBOSE}" != "no" ] && echo "Converted relative linktarget to absolute path -${TNAME}-."
-        } || {
-        TNAME="${NEWNAME}"
-        [ "${VERBOSE}" != "no" ] && echo "Using absolute link target -${TNAME}-."
-        }
-      }
-
-    case "${TTYPE}" in
-      "f")  [ "${VERBOSE}" != "no" ] && echo "Creating file -${TNAME}-."
-            create_file "${TNAME}" &
-	    ;;
-      "d")  [ "${VERBOSE}" != "no" ] && echo "Creating directory -${TNAME}-."
-            mk_dir "${TNAME}"
-	    # Add check to see if there's an entry in fstab to mount.
-	    ;;
-      *)    [ "${VERBOSE}" != "no" ] && echo "Invalid type -${TTYPE}-."
-            continue
-	    ;;
-    esac
-
-
-    done
-
-  return 0
-
-  }
-
-clearcache=0
-exec 9</proc/cmdline
-while read line <&9
-do
-	case "$line" in
-		*clearcache*)  clearcache=1
-			       ;;
-		*)	       continue
-			       ;;
-	esac
-done
-exec 9>&-
+	cat ${CFGFILE} | grep -v "^#" | sed -e '/^$/ d' | \
+		while read LINE; do
+		eval `echo "$LINE" | sed -n "s/\(.*\)\ \(.*\) \(.*\)\ \(.*\)\ \(.*\)\ \(.*\)/TTYPE=\1 ; TUSER=\2; TGROUP=\3; TMODE=\4; TNAME=\5 TLTARGET=\6/p"`
+		TNAME=${ROOT_DIR}/${TNAME}
+		[ "${VERBOSE}" != "no" ] && echo "Checking for -${TNAME}-."
+
+		[ "${TTYPE}" = "l" ] && {
+			TSOURCE="$TLTARGET"
+			[ "${VERBOSE}" != "no" ] && echo "Creating link -${TNAME}- pointing to -${TSOURCE}-."
+			link_file "${TSOURCE}" "${TNAME}"
+			continue
+		}
+		case "${TTYPE}" in
+			"f")  [ "${VERBOSE}" != "no" ] && echo "Creating file -${TNAME}-."
+				create_file "${TNAME}"
+				;;
+			"d")  [ "${VERBOSE}" != "no" ] && echo "Creating directory -${TNAME}-."
+				mk_dir "${TNAME}"
+				;;
+			*)    [ "${VERBOSE}" != "no" ] && echo "Invalid type -${TTYPE}-."
+				continue
+				;;
+		esac
+	done
+	return 0
+}
 
-if test -e /etc/volatile.cache -a "$VOLATILE_ENABLE_CACHE" = "yes" -a "x$1" != "xupdate" -a "x$clearcache" = "x0"
+if test -e ${ROOT_DIR}/etc/volatile.cache -a $VOLATILE_ENABLE_CACHE = yes -a x$1 != xupdate
 then
-	sh /etc/volatile.cache
+	sh ${ROOT_DIR}/etc/volatile.cache
 else	
-	rm -f /etc/volatile.cache /etc/volatile.cache.build
+	rm -f ${ROOT_DRI}/etc/volatile.cache ${ROOT_DIR}/etc/volatile.cache.build
 	for file in `ls -1 "${CFGDIR}" | sort`; do
 		apply_cfgfile "${CFGDIR}/${file}"
 	done
 
-	[ -e /etc/volatile.cache.build ] && sync && mv /etc/volatile.cache.build /etc/volatile.cache
+	[ -e ${ROOT_DIR}/etc/volatile.cache.build ] && sync && mv ${ROOT_DIR}/etc/volatile.cache.build ${ROOT_DIR}/etc/volatile.cache
 fi
 
-if test -f /etc/ld.so.cache -a ! -f /var/run/ld.so.cache
+if [ "${ROOT_DIR}" = "/" ] && [ -f /etc/ld.so.cache ] && [ ! -f /var/run/ld.so.cache ]
 then
 	ln -s /etc/ld.so.cache /var/run/ld.so.cache
 fi

index 4f76cb4..3b5a47f 100755
@@ -54,14 +54,7 @@ fi
 
 #
 # This is as good a place as any for a sanity check
-# /tmp should be a symlink to /var/tmp to cut down on the number
-# of mounted ramdisks.
-if test ! -L /tmp && test -d /var/tmp
-then
-	rm -rf /tmp
-	ln -sf /var/tmp /tmp
-fi
-
+#
 # Set the system clock from hardware clock
 # If the timestamp is more recent than the current time,
 # use the timestamp instead.

index e0741aa..f7e2ef7 100644
@@ -31,6 +31,7 @@ l root root 1777 /var/lock /var/volatile/lock
 l root root 0755 /var/log /var/volatile/log
 l root root 0755 /var/run /var/volatile/run
 l root root 1777 /var/tmp /var/volatile/tmp
+l root root 1777 /tmp /var/tmp
 d root root 0755 /var/lock/subsys none
 f root root 0664 /var/log/wtmp none
 f root root 0664 /var/run/utmp none

new file mode 100644
index 0000000..3a295ee
@@ -0,0 +1,19 @@
+#!/bin/sh
+
+. /etc/default/rcS
+
+[ "$ROOTFS_READ_ONLY" = "no" ] && exit 0
+
+# Make sure unionfs is in /proc/filesystems
+if ! grep -q unionfs /proc/filesystems; then
+    echo "ERROR: unionfs not supported by kernel!"
+    exit 1
+fi
+
+mkdir -p /var/volatile/lib
+mount -t unionfs -o dirs=/var/volatile/lib:/var/lib=ro none /var/lib
+
+if [ $? != 0 ]; then
+    echo "ERROR: Union mount failed!"
+    exit 1
+fi

index 6e15f88..a8b093b 100644
@@ -28,6 +28,7 @@ SRC_URI = "file://functions \
            file://sysfs.sh \
            file://device_table.txt \
            file://populate-volatile.sh \
+           file://read-only-rootfs-hook.sh \
            file://volatiles \
            file://save-rtc.sh \
            file://GPLv2.patch"

@@ -82,6 +83,7 @@ do_install () {
 	install -m 0755    ${WORKDIR}/devpts		${D}${sysconfdir}/default
 	install -m 0755    ${WORKDIR}/sysfs.sh		${D}${sysconfdir}/init.d
 	install -m 0755    ${WORKDIR}/populate-volatile.sh ${D}${sysconfdir}/init.d
+	install -m 0755    ${WORKDIR}/read-only-rootfs-hook.sh ${D}${sysconfdir}/init.d
 	install -m 0755    ${WORKDIR}/save-rtc.sh	${D}${sysconfdir}/init.d
 	install -m 0644    ${WORKDIR}/volatiles		${D}${sysconfdir}/default/volatiles/00_core
 	if [ "${TARGET_ARCH}" = "arm" ]; then

@@ -124,6 +126,7 @@ do_install () {
 	ln -sf		../init.d/sysfs.sh	${D}${sysconfdir}/rcS.d/S02sysfs.sh
 	# udev will run at S03 if installed
 	ln -sf		../init.d/populate-volatile.sh	${D}${sysconfdir}/rcS.d/S37populate-volatile.sh
+	ln -sf		../init.d/read-only-rootfs-hook.sh  ${D}${sysconfdir}/rcS.d/S41read-only-rootfs-hook.sh
 	ln -sf		../init.d/devpts.sh	${D}${sysconfdir}/rcS.d/S38devpts.sh
 	if [ "${TARGET_ARCH}" = "arm" ]; then
 		ln -sf	../init.d/alignment.sh	${D}${sysconfdir}/rcS.d/S06alignment.sh