How to perform an efs/imei backup before flashing custom ROM

Estimated read time 2 min read

Here is a useful tool to take a backup of your EFS folder which stores your imei infomation . There is a probability that you could corrupt your efs parition ( i just did recently ) and inorder to restore/fix your imei this tool is helpful.

Before you flash a custom ROM, make sure you backup your EFS using this tool. The backup would be stored as efs.img in your sd folder which you could restore in a click if your efs is corrupt.


So, what does this do?

  • Dump current kernel (and recovery on devices having a seperate one)
  • Flash kernel from /sdcard/zImage
  • Flash recovery from /sdcard/recovery.bin
  • Backup EFS
    (as raw .IMG dump and as .TAR archive)
  • Check/Verify EFS backup (i.e. compare to “live” EFS)
  • Restore EFS from either .IMG or .TAR
  • Open stock update .TARs and flash from from it:
    – Modem Firmware
    – Kernel
  • Reboot device
    – normally
    – to recovery
    – to download mode

*) When you check the EFS backup right after you made it, it should show a 100% match to the current phone’s EFS.
However, after a reboot, the EFS *does* start to differ a bit – that seems to be normal, during my tests the EFS differed for 80bytes more after each reboot, my original EFS dump even differed by ~150k already 

kTool companion tool market link Show ]

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