Add overlayfs setup for /etc and /var/lib

Signed-off-by: David Oberhollenzer <david.oberhollenzer@tele2.at>

cfg/rpi3/linux.config

@@ -5183,7 +5183,7 @@ CONFIG_OCFS2_FS_USERSPACE_CLUSTER=m
 CONFIG_OCFS2_FS_STATS=y
 CONFIG_OCFS2_DEBUG_MASKLOG=y
 # CONFIG_OCFS2_DEBUG_FS is not set
-CONFIG_BTRFS_FS=m
+CONFIG_BTRFS_FS=y
 CONFIG_BTRFS_FS_POSIX_ACL=y
 # CONFIG_BTRFS_FS_CHECK_INTEGRITY is not set
 # CONFIG_BTRFS_FS_RUN_SANITY_TESTS is not set
@@ -5220,7 +5220,9 @@ CONFIG_QUOTACTL=y
 CONFIG_AUTOFS4_FS=y
 CONFIG_FUSE_FS=m
 CONFIG_CUSE=m
-CONFIG_OVERLAY_FS=m
+CONFIG_OVERLAY_FS=y
+# CONFIG_OVERLAY_FS_REDIRECT_DIR is not set
+# CONFIG_OVERLAY_FS_INDEX is not set
 
 #
 # Caches

pkg/initrd/initrd.skel

@@ -10,6 +10,7 @@ busybox mount -t devtmpfs none /dev
 
 root_sfs=""
 root=""
+overlay_dev=""
 singleuser=0
 
 for param in `cat /proc/cmdline`; do
@@ -20,6 +21,9 @@ for param in `cat /proc/cmdline`; do
 	root_sfs=*)
 		root_sfs="${param##root_sfs=}"
 		;;
+	overlay_dev=*)
+		overlay_dev="${param##overlay_dev=}"
+		;;
 	single*)
 		singleuser=1
 		;;
@@ -41,6 +45,20 @@ while [ ! -e ${root} ]; do
 	busybox sleep 1
 done
 
+# file system setup
+overlay_mount() {
+	local lower=/newroot/${1}
+	local upper=/newroot/${2}
+	local work=/newroot/${2}_work
+	local target=/newroot/${3}
+
+	mount -t overlay overlay -olowerdir=${lower},upperdir=${upper},workdir=${work} ${target}
+}
+
+bind_mount() {
+	mount --bind /newroot/${1} /newroot/${2}
+}
+
 mount ${root} /images
 
 if [ ! -e /images/${root_sfs} ]; then
@@ -68,6 +86,21 @@ mkdir -p /newroot/var/tmp
 ln -s /run /newroot/var/run
 ln -s /run/lock /newroot/var/lock
 
+if [ ! -z "$overlay_dev" ]; then
+	while [ ! -e ${overlay_dev} ]; do
+		echo "Waiting for overlay device"
+		busybox sleep 1
+	done
+
+	mount ${overlay_dev} /newroot/cfg/overlay
+
+	overlay_mount "cfg/preserve/etc" "cfg/overlay/etc" "etc"
+	overlay_mount "cfg/preserve/var_lib" "cfg/overlay/var_lib" "var/lib"
+else
+	bind_mount "cfg/preserve/etc" "etc"
+	bind_mount "cfg/preserve/var_lib" "var/lib"
+fi
+
 # cleanup mounts
 umount -l /images
 umount -l /dev

pkg/release-alix/syslinux.cfg

@@ -3,4 +3,4 @@ totaltimeout 50
 default linux
 label linux
  kernel /KERNELFILE
- append root=/dev/sda1 root_sfs=/ROOTFSFILE
+ append root=/dev/sda1 overlay_dev=/dev/sda2 root_sfs=/ROOTFSFILE

pkg/release-rpi3/cmdline.txt

@@ -1 +1 @@
-console=serial0,115200 console=tty0 root=/dev/mmcblk0p1 elevator=deadline rootwait root_sfs=ROOTFSFILE
+console=serial0,115200 console=tty0 root=/dev/mmcblk0p1 elevator=deadline rootwait root_sfs=ROOTFSFILE overlay_dev=/dev/mmcblk0p2

pkg/rootfs-alix/build

@@ -4,7 +4,9 @@ build() {
 	local DEPLOY="$3"
 
 	# setup skeleton
-	mkdir -pv ${BUILD}/{bin,etc,dev,sys,proc,tmp,var,run}
+	mkdir -pv ${BUILD}/{bin,lib,etc,dev,sys,proc,tmp,var,run}
+	mkdir -pv ${BUILD}/{boot,usr,srv,mnt,opt}
+	mkdir -pv ${BUILD}/cfg/{preserve,overlay}
 
 	echo "/lib" > "$BUILD/etc/ld-musl-i386.path"
 
@@ -22,6 +24,12 @@ build() {
 
 		cp -ru --remove-destination ${PKGDEPLOYDIR}/${pkgname}/* "$BUILD"
 	done < "$BUILD/etc/packages"
+
+	# move configuration to preserve directory
+	mv ${BUILD}/etc ${BUILD}/cfg/preserve
+	mkdir -p ${BUILD}/etc
+
+	mv ${BUILD}/var/lib ${BUILD}/cfg/preserve/var_lib
 }
 
 deploy() {

pkg/rootfs-rpi3/build

@@ -4,7 +4,9 @@ build() {
 	local DEPLOY="$3"
 
 	# setup skeleton
-	mkdir -pv ${BUILD}/{bin,etc,dev,sys,proc,tmp,var,run}
+	mkdir -pv ${BUILD}/{bin,lib,etc,dev,sys,proc,tmp,var,run}
+	mkdir -pv ${BUILD}/{boot,usr,srv,mnt,opt}
+	mkdir -pv ${BUILD}/cfg/{preserve,overlay}
 
 	echo "/lib" > "$BUILD/etc/ld-musl-arm.path"
 	echo "/opt/vc/lib" >> "$BUILD/etc/ld-musl-arm.path"
@@ -23,6 +25,12 @@ build() {
 
 		cp -ru --remove-destination ${PKGDEPLOYDIR}/${pkgname}/* "$BUILD"
 	done < "$BUILD/etc/packages"
+
+	# move configuration to preserve directory
+	mv ${BUILD}/etc ${BUILD}/cfg/preserve
+	mkdir -p ${BUILD}/etc
+
+	mv ${BUILD}/var/lib ${BUILD}/cfg/preserve/var_lib
 }
 
 deploy() {