If you want to fully backup your current ROM on your Galaxy S4 then you should make a Nandroid Backup.
Nandroid Backups are very useful especially when you want to flash a new kernel or a custom ROM because if something goes wrong just restore the backup your performed before.
But how to perform a Nandroid Backup on your Galaxy S4? It is very easy.
Follow the guide below
1. Turn off your Samsung Galaxy S3
2. Press and hold Volume Up + Home + Power buttons at the same time.
3. Release all buttons when you see SGS3 Logo.
4. Custom Recovery will be loaded then.
5. Select Backup and Recovery and then press Backup.
6. That’s it. The Backup will take some time till it’s fully finished.
7. If you want to restore the Backup your performed select Restore.
Have a question? Leave a comment below.