After some research I discovered that backing up the '/efs' folder using existing tools such as my EFS Pro application will not work with this particular device.
Most Samsung devices have a file in the '/efs' folder called 'nv_data.bin' and on closer inspection this file is not present on our devices.
This is because the I9305 has LTE which also means its fitted with a Qualcomm chip to control the modem. This also means that our device uses a Qualcomm RIL instead of the usual Samsung RIL so the NV area of the device including the EFS structure is laid out different.
As it happens our device is not much different from some US variants of the Galaxy S III except we have the Quad Core Exynos CPU in the I9305 where as some US variants are fitted with a Dual Core Snapdragon.
Setting up QPST with your PC:
- Dial *#7284# on your phone to access PhoneUtil and select 'Qualcomm USB Settings' at the bottom. Now select 'RNDIS + DM + MODEM' and press 'OK' to return to the previous screen. Now press your 'Back' key to exit PhoneUtil. Your phone is now in DIAG Mode.
- Download and Install: SAMSUNG_USB_Driver_for_Mobile_Phones_1590.exe - 23.06 MB if you don't already have Kies or a USB Driver installed.
- Download and Install: QPST v2.7.378.zip - 14.68 MB
- Now connect your phone to the PC with a USB cable and wait for Drivers to install.
- Start the 'QPST Configuration' application and select the 'Ports' tab then press the 'Add New Port...' button. Select the COM Port that has 'USB/QC Diagnostic' next to it, change the Port Label if you like to 'Samsung GT-I9305' then press 'OK'. You should now see your phone listed in the 'Ports' tab and the 'State' should indicate 'Enabled'. You can now Close this application.
Backing Up IMEI / NV Data:
- Start the 'Software Download' application and select the 'Backup' tab.
- Press the 'Browse' button and choose a Save Location for your QCN File.
- Press the 'Start' button and wait for it to finish. This will back up all your phones NV Items and save them to the QCN Backup File.
- The resulting QCN Backup File should be 250KB.
Restoring IMEI / NV Data:
- Start the 'Software Download' application and select the 'Restore' tab.
- Press the 'Browse' button and select your QCN Backup File.
- Press the 'Start' button and wait for it to finish. This will restore all your phones NV Items from the QCN Backup File.
- Your IMEI / NV Data should now be fully restored. Dial *#06# on your phones keypad to check your IMEI is restored.
Restore USB Settings after Backup / Restore:
- Dial *#7284# on your phone to access PhoneUtil and select 'Qualcomm USB Settings' at the bottom. Now select 'MTP + ADB' and press 'OK' to return to the previous screen. Now press your 'Back' key to exit PhoneUtil. Your phone is now back to default USB operation.
Quote: If the 'Qualcomm USB Settings' Button is missing from the PhoneUtil application then execute the following command in a Terminal Emulator to launch the Qualcomm USB Settings page directly:
su -c 'am start -n com.sec.android.app.phoneutil/com.sec.android.app.phoneutil.USBSettings'
Please Note: You must be rooted or this command will not work.
Quote: After looking closely at the partition table of the I9305 I noticed there are more partitions relating to 'efs' that may also be worth backing up aswell as a precaution. These are:
- EFS - Located at: '/dev/block/mmcblk0p3'
(This partition is mounted in root of device at '/efs'. There is also a '/factory' folder present which appears to be linked to '/efs'. You can backup this partition with my EFS Pro application.)
- m9kefs1 - Located at: '/dev/block/mmcblk0p4'
- m9kefs2 - Located at: '/dev/block/mmcblk0p5'
- m9kefs3 - Located at: '/dev/block/mmcblk0p6'
(These partitions are unknown as to their use and data content at present. I have examined these and noticed that these 'm9kefs' partitions all share the same 16 byte header information. I also found that these partition areas contain data only and have no specific file system. Until we know what these partitions are used for, it may be worth backing these up aswell for safety.)
You can back these up by using the 'dd' command from a Terminal Emulator:
su -c 'dd if=/dev/block/mmcblk0p4 of=/sdcard/m9kefs1.bin'
su -c 'dd if=/dev/block/mmcblk0p5 of=/sdcard/m9kefs2.bin'
su -c 'dd if=/dev/block/mmcblk0p6 of=/sdcard/m9kefs3.bin'
Resulting '*.bin' files from these partitions should be 4MB.
You can also restore the backups using the 'dd' command from a Terminal Emulator:
su -c 'dd if=/sdcard/m9kefs1.bin of=/dev/block/mmcblk0p4'
su -c 'dd if=/sdcard/m9kefs2.bin of=/dev/block/mmcblk0p5'
su -c 'dd if=/sdcard/m9kefs3.bin of=/dev/block/mmcblk0p6'
Please Note: You must be Rooted to Backup and Restore these partitions.
Recovering IMEI And Data Connection After Flashing WRONG Root Package Intended For I9300:
- Make sure you have Samsung Kies or the Samsung USB Driver installed on your PC.
- Download and Extract: Odin3 3.04.zip - 457.11 KB to your PC if you don't already have it.
- Download and Extract: Param_Bin_I9305.zip - 612.14 KB to your PC.
- With your Phone Switched Off, press and hold: 'VOL DN' + 'HOME' + 'POWER' to enter Download Mode.
- Connect your phone to your PC via USB Cable and start Odin.
- Check your phone is connected by seeing if a COM Port in a Blue box is present under ID:COM.
- Press the 'PDA' Button and select the 'Param_Bin_I9305.tar.md5' file you extracted from the Zip Archive earlier.
- Press the 'Start' Button and wait for it to finish flashing. If successful, you will see a Green Box with 'PASS!'.
- Wait for your phone to reboot then go to your Dialer and press: *#06#. You should now see your IMEI and your Data Connection will be back.
retirado de xda-developers.