Very Important!! Step Before Custom Rom

Before proceeding with Custom ROMs make sure to

!! BACKUP STOCK ROM IMAGES FIRST !!

1. Root your device : Rooting Guide
2. Open cmd on Platform tools folder and paste following command

   adb shell

   su

   dd if=/dev/block/by-name/super of=/sdcard/super.img

   dd if=/dev/block/by-name/persist of=/sdcard/persist.img

   Info! -2 files will be saved to internal storage. Keep them safe.
   -The super image will be around 14-15 GB and persist around 30-40 MB.
3. Done

Important! -Although super images are identical to all but persist are not.
-Persist.img store fingerprint data and other unique data of your device so keep persist safe at all costs. It will be needed in case you lose VoLTE or fingerprint.
-Super images are large so downloading them would be a problem, so better to save them in your local storage and take backups of newer super images with newer stock updates. As this stock Super.img will be used to get back to Stock Rom(OOS).