use overlayfs for /etc

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

@@ -1,7 +1,7 @@
 hostname = "diya"
 do_install:append () {
     cat >> ${D}${sysconfdir}/fstab <<EOF
-# add bind mount for /etc
-/etc /var/etc none defaults,bind 0 0
+# add overlay for /etc
+overlay /etc overlay defaults,nofail,lowerdir=/etc,upperdir=/var/etc/upper,workdir=/var/etc/work 0 2
 EOF
 }

recipes-core/init-ifupdown/files/itf_diya

@@ -10,7 +10,7 @@ iface wlan0 inet dhcp
 # wireless_mode managed
 # wireless_essid any
 # wpa-driver wext
-wpa-conf /var/etc/network/wpa_supplicant.conf
+wpa-conf /etc/network/wpa_supplicant.conf
 
 # Ethernet/RNDIS gadget (g_ether)
 # ... or on host side, usbnet and random hwaddr

recipes-core/init-ifupdown/init-ifupdown_%.bbappend

@@ -1,9 +1,7 @@
 FILESEXTRAPATHS:prepend := "${THISDIR}/files:"
-SRC_URI += "file://itf_diya"
+SRC_URI += " file://itf_diya "
 
 do_install:append () {
-    install -d ${D}/var/etc
-    install -d ${D}/var/etc/network
     rm ${D}/etc/network/interfaces
-    install -m 0644 ${WORKDIR}/itf_diya ${D}/var/etc/network/
+    install -m 0644 ${WORKDIR}/itf_diya ${D}/etc/network/interfaces
 }