package/skeleton-init-openrc: add support to remount rootfs as rw

Add a pseudo entry for /dev/root in fstab, to tell openrc to properly
remount or not remount / read-write.

For consistency with systemd (which is the only other init system to
tweak an fstab basd on / being rw or not), we do this change in the
openrc skeleton rather than in the openrc package.

Signed-off-by: Michał Łyszczek <michal.lyszczek@bofc.pl>
[yann.morin.1998@free.fr:
  - tweak the sed expressions
  - reword commit log
]
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/skeleton-init-openrc/skeleton-init-openrc.mk

@@ -15,8 +15,23 @@ SKELETON_INIT_OPENRC_DEPENDENCIES = skeleton-init-common
 
 SKELETON_INIT_OPENRC_PROVIDES = skeleton
 
+ifeq ($(BR2_TARGET_GENERIC_REMOUNT_ROOTFS_RW),y)
+# Comment /dev/root entry in fstab. When openrc does not find fstab entry for
+# "/", it will try to remount "/" as "rw".
+define SKELETON_INIT_OPENRC_ROOT_RO_OR_RW
+	$(SED) '\:^/dev/root :s/^/# /' $(TARGET_DIR)/etc/fstab
+endef
+else
+# Uncomment /dev/root entry in fstab which has "ro" option so openrc notices
+# it and doesn't remount root to rw.
+define SKELETON_INIT_OPENRC_ROOT_RO_OR_RW
+	$(SED) '\:^# /dev/root:s/^# //' $(TARGET_DIR)/etc/fstab
+endef
+endif # BR2_TARGET_GENERIC_REMOUNT_ROOTFS_RW
+
 define SKELETON_INIT_OPENRC_INSTALL_TARGET_CMDS
 	$(call SYSTEM_RSYNC,$(SKELETON_INIT_OPENRC_PKGDIR)/skeleton,$(TARGET_DIR))
+	$(SKELETON_INIT_OPENRC_ROOT_RO_OR_RW)
 endef
 
 $(eval $(generic-package))

package/skeleton-init-openrc/skeleton/etc/fstab

@@ -1,3 +1,4 @@
 # <file system>	<mount pt>	<type>	<options>	<dump>	<pass>
+/dev/root	/		ext2	ro,noauto	0	0
 tmpfs		/tmp		tmpfs	mode=1777	0	0
 tmpfs		/run		tmpfs	mode=0755,nosuid,nodev	0	0