If you're thinking about rooting your phone (for whatever reason), there are several vital things you need to know. One of these is called the
nandroid backup.
A nandroid is your lifesaver... it takes a snapshot image of the device's entire current state, as it is right then, and saves it in a .zip file on your memory card or internal memory. I recommend all nandroid backups get saved to the external memory card, and copied to a PC or jump drive for safe keeping.
Once you root and have a custom recovery installed, your FIRST action should be to backup the phone in its pristine, stock rooted state. Save that as your baseline backup. Make backups regularly: at least every two weeks if not weekly, and especially before installing a new ROM or changing ANYTHING in the /system partition.
* -Let me say that again because it's
IMPORTANT! Before you change ANYTHING in /system, STOP and make a nandroid backup in Recovery! It may be a trouble, but bricking your phone is even more trouble. -
*
Both ClockworkMod and TWRP Recoveries have Backup capability. These .zip files can eat up your memory card quickly because they're large. As long as you're copying them all to the PC, you need only keep three on your card: the original stock rooted backup, and your two most recent backups. If the last one is somehow corrupted, you can always restore the one just before that without losing everything.
Want to ignore this advice because you're in a hurry? Here's what will happen.
If you STILL decide to change something in /system and you don't have a backup, you will have forever altered how your phone works... and it might not work at all. You can't get that original file back: and no, a factory reset won't fix it (that only deletes the /data partition and does not touch /system) and you will have a broken phone on your hands with only a couple of possible solutions... and none of them are fast, cheap or easy.
So save yourself from having to buy a new phone or sending yours to a distant repair facility for a costly re-flash to stock... make nandroid backups often. You can never have too many nandroids. You CAN have too few.
If you have any questions about nandroid backups, just ask! We're all here to help you, and we'd much rather help you learn how to make nandroids than help you TRY to restore your bricked phone because no nandroid is available.
For even more information on rooting (and you need to read & learn as much as you can before you start), read this great post:
http://androidforums.com/threads/rooting-best-practices.450904/
And remember: if you're unsure of what you're doing,
STOP. Ask questions BEFORE you proceed! The last thing you want to have happen is to be in the middle of a system rewrite and your battery die on you while you're frantically asking questions. We're here to help you learn!