[Galaxy Grand Duos i9082 General] xenon92:
EFS BACKUP AND RESTORE​

for

GALAXY GRAND i9082 and i9082L​

DISCLAIMER: I am not responsible if you mess up your phone by following steps wrongly. This guide is to help you backup one of the most important partitions on your phone.

This is the FIRST THING that you should do after you root your Galaxy Grand i9082 or i9082L.

This method is ROM INDEPENDENT. It can be performed on any ROM.​

Check post #2 below for the EFS BACKUP APP developed by me.

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What is so important about EFS and why you SHOULD backup your EFS?

EFS is a system folder in the root directory of your phone that contains very important and basic information about your device's identity like Wi-Fi MAC address, Bluetooth MAC address and the MOST IMPORTANT - IMEI address (nv_data.bin).

Now if this EFS partition accidentally gets corrupted or erased, your phone’s IMEI number will get erased and your device will become completely useless and you won't be able to make voice call further, as the carrier network will not recognize your phone. This can happen for a variety of reasons, sometimes flashing a wrong or corrupted ROM. This kind of damage is not accepted by the service center. Only solution that the service center provides is to replace the motherboard of the device and that costs a lot of $$$!

Only a BACKUP of your EFS can save your phone if something goes wrong with your EFS partition.

(Some of you have already messed up your IMEI. Check Troubleshooting forum for details.)

Below is the correct and the safest method to backup your EFS folder. Copying the "/efs" directory to an external SD card using a root file manager is NOT the correct way as it will mess up the permissions when you restore it back.

NOTE

: While some phones have ([MENTION=943196]k2wl[/MENTION]), some of the phones (including mine and [MENTION=3599602]DBZo07[/MENTION]) don't have "nv_data.bin" in their "/efs" partition. Even though our IMEI are intact, but this file seems to be missing from "/efs". I am still looking into it as to why it is missing from EFS. I'll update the OP when i am more clear about the reason. Nonetheless, backing up EFS is still an important task and should be performed as soon as you get root permissions on your phone.

BACKUP

1. Open Terminal Emulator.

2. Type the following and press ENTER on your keyboard to grant Terminal Emulator SuperUser permission.

su

3. Type the following and press ENTER on your keyboard (case sensitive - so type it just as it is written here)

dd if=/dev/block/mmcblk0p17 of=/storage/sdcard0/efs.img bs=4096

If successfully executed, you will see something like this.

You will get "efs.img" file in your internal memory (sdcard0) of size 20 MB. Move this "efs.img" file to someplace safe - Laptop or Online backup so that it is readily available if you need it.

RESTORE

1. Make sure "efs.img" file is available in your internal memory (sdcard0).

2. Follow steps 1 and 2 from above to grant Terminal Emulator SuperUser permissions.

3. Type the following and press ENTER on your keyboard (case sensitive - so type it just as it is written here)

dd if=/storage/sdcard0/efs.img of=/dev/block/mmcblk0p17 bs=4096

4. Reboot

You'll have one thing less to worry before trying/flashing something new on your Galaxy Grand i9082.

Don't forget to press Thanks! :good:

Credits:

dr.ketan​