use overlayfs for /etc

recipes-core/base-files/base-files_%.bbappend

@@ -1,7 +1 @@
-hostname = "diya"
-do_install:append () {
-    cat >> ${D}${sysconfdir}/fstab <<EOF
-# add overlay for /etc
-overlay /etc overlay defaults,nofail,lowerdir=/etc,upperdir=/var/etc/upper,workdir=/var/etc/work 0 2
-EOF
-}
+hostname = "diya"