add custom DNS support and avoid overwriting

ack-centos.json

@@ -28,9 +28,10 @@
         "scripts/reboot.sh",
         "scripts/cleanUpKerneles.sh",
         "config/default.sh",
+        "scripts/updateDNS.sh",
         "scripts/verify.sh"
       ],
       "expect_disconnect": true
     }
   ]
-}
+}

scripts/updateDNS.sh

@@ -0,0 +1,10 @@
+#!/bin/bash
+
+# unlock DNS file in case it was locked
+# chattr -i /etc/resolv.conf
+
+# Using your custom nameserver to replace xxx.xxx.xxx.xxx
+# echo "nameserver xxx.xxx.xxx.xxx\nnameserver xxx.xxx.xxx.xxx" > /etc/resolv.conf
+
+# Keep resolv locked to prevent overwriting by cloudinit/NetworkManager
+# chattr +i /etc/resolv.conf