A script that attempts to extract nv_data.bin files from an EFSv2 partition image. The discussion below is applicable to the Samsung i9300 intl. GSM. However, it may be relevant to other devices as well.
The script should work in the following cases
- You have accidentally formatted your EFS partition incorrectly, but haven't written anything to it (for example, when it's been formatted through Swapper for Root and thus corrupted.
- You have a corrupted the EFS partition through some other means
- Possibly, when the phone is stuck during boot, despite having flashed the stock rom
You know that the EFS partition has been corrupted when,
- You are stuck and cannot boot (mine was stuck at the bootloader
Samsung i9300image when I had CyanogenMod installed) - If you're on stock, you are stuck at the Samsung logo with a flashing blue indicator light
- and you should see the following error when you boot into the stock Samsung recovery:
E:failed to mount /efs (Invalid argument)
The script will not be of any help, since the device has already restored its default EFS files.
I have only tested the tool on Samsung i9300 intl. (S3), GSM with EFSv2. It may or may not work with EFSv1.
- Ubuntu / Debian / other *nix operating system
- Python 2.7
- Install a custom recovery, I used CWM (You can skip this step if you have already done so)
- Make a full efs backup from a terminal emulator (I used AROMA, to get a terminal emulator)
dd if=/dev/block/mmcblk0p3 of=/storage/sdcard1/efs_broken.img
- Format your EFS partition using a terminal emulator from recovery (Again, I used AROMA)
mke2fs /dev/block/mmcblk0p3
- Restart the phone, you should now be able to boot into your phone. Wait till you reach the homescreen then continue with the instructions.
- Boot back into recovery, then backup your EFS partion again. This backup provides us with a working default which we shall use later.
dd if=/dev/block/mmcblk0p3 of=/storage/sdcard1/efs_default.img
- Copy over the EFS dumps to your computer
- Next, execute the following on your computer
sudo python efs_recover.py efs_broken.img -g efs_default.img
- If the execution was successful you should see recovered_efs_X.img files have been generated. Where X is the number of the image.
- Place the recovered_efs_x.img files on your sdcard
- Reboot your phone into recovery and enter the terminal emulator (AROMA). Decide on a recovered image to use. Replace X with the number you choose
dd if=/storage/sdcard1/recovered_efs_X.img of=/dev/block/mmcblk0p3
- Reboot your phone, go into
Aboutand see if your IMEI was restored, if not, repeat steps 10 and 11 with a different image.
To see help for the script, execute
python efs_recover.py -h
I drew from the knowledge and effort of others in this project. The major contribution was an XDA forum thread by SlashV Successful IMEI repair on i9300 without backup.