[OE-core] [PATCH 1/4] image.bbclass: add a hook funtion to support readonly rootfs

[Qi.Chen at windriver.com]

From: Chen Qi <Qi.Chen at windriver.com>

read_only_rootfs_hook: this funtion is invoked only if 'read-only-rootfs'
is in IMAGE_FEATURES. It tweaks some basic files and makes populate-
volatile.sh script run at rootfs time.

For now, it has real effect only if the init system is sysvinit.

[YOCTO #3406]

Signed-off-by: Chen Qi <Qi.Chen at windriver.com>
---
 meta/classes/image.bbclass |   18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/meta/classes/image.bbclass b/meta/classes/image.bbclass
index dd78acb..7d533b6 100644
--- a/meta/classes/image.bbclass
+++ b/meta/classes/image.bbclass
@@ -233,6 +233,24 @@ 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
-- 
1.7.9.5