1. Download official 4.1.2 from http://download.andreavenditti.com/grouper/rom/Stock_4.1.2_JZO5
and 4.2 OTA image from http://android.clients.google.com/packages/data/ota/google_naka
2. Boot into CWM
3. install 4.1.2, don't forget to turn on root in the installer
4. reboot check that root is fully working
5. reboot into recovery install 4.2
6. before reboot CWM will ask to disable recovery flash and protect root.
Answer yes to both questions
关于为什么要重新装4.1.2，主要是因为4.1.2有的系统文件可能被改动过，
装4.2 OTA包的时候，文件检查的script通不过显示有assert failed，
如果安装4.2更新的时候没问题，就不需要重新装stock 4.1.2了。
