How to backup the Galaxy S3 IMEI and /efs folder

The /efs directory contains the phone's IMEI, which is part of the system that identifies your phone and what network to connect to. From time to time, this gets deleted during the various wipes and/or custom ROM installations. You won't want the /efs directory deleted at all. To be safe, you need to back it up.

On the Samsung Galaxy S3, backing up the EFS folder has become easy these days, thanks to a tool provided by XDA Developers member i9000.

The EFS backup/restore tool is a simple tool that you can use on your PC. It's an executable script that fetches your phone's EFS data and then stores it on your computer as an image file. Then, should you need it later, you can restore it using a similar executable script. When restoring, just make sure that the image file is in the same folder as the other files.

It works like a charm! Try it out and feel a lot safer flashing different ROMs. If you encounter an error, you may have an newer version of ADB installed. In that case, you should use the other version of the tool provided.

This guide shows you how to backup the Galaxy S3 IMEI and /efs folder.

Warning

The instructions in this guide are intended for use with the Samsung Galaxy S3 and all of its variants. Applying these instructions on another device or model may produce undesired outcomes.
The information in this guide is provided for instructional and educational purposes only. There is no guarantee that these instructions will work under your specific and unique circumstances.
Use these instructions at your own risk. We shall not hold any responsibility or liability for whatever happens to you or your device arising from your use of the info in this guide.
Read and understand the whole guide first before actually performing the instructions.

Requirements

Samsung Galaxy S3 (any variant) with root access. You may refer to the following guides:
A Windows PC, with RAR extraction software installed (e.g., WinRAR, 7-Zip)
Handset USB drivers installed on the PC. You may install the drivers by installing Samsung Kies.
Download the EFS Backup/Restore tool for the Galaxy S3 (EFS_Backup_Restore_new_ADB.rar, 155.5 kB) to your PC.
Make sure your device's battery still has at least 70% power. You don't want the device to shut down in the middle of the procedure.
Backup all personal data on your phone to make sure you have a copy of your personal data (e.g., contacts, SMS, MMS, Internet settings, Wi-Fi passwords, and the like) in case the procedure in this guide erases such data.
- For backup tips, check our guides on how to sync your data to the cloud and how to create local backups of your mobile data.

Instructions

Open the RAR file and extract all of its contents into a folder.
On your phone, enable USB debugging by going to Settings > Developer Options > USB debugging.
Connect the phone to your computer.
On the computer, go to the extraction folder and double-click on the appropriate BAT script:
- To backup /efs, run Backup_EFS.bat.
  - The script will save the backup file as efs.img inside the same folder as Backup_EFS.bat.
- To restore your previous backup of /efs, run Restore_EFS.bat.
  - Make sure that your backup image (efs.img) is in the same folder as Restore_EFS.bat.