How to backup / restore Samsung Galaxy S3 EFS?

You can ignore this article if you did not root Samsung Galaxy S III. Why? Because you need root access to backup and restore Samsung Galaxy S3 EFS. And you don’t need to worry about EFS at all when not rooted.

What is EFS? It is a place that stores your Android smartphone important data like Wi-Fi, Bluetooth MAC address and IMEI (nv_data.bin). Do take note if you are a frequent ROM / firmware flasher or rooted your Android phone. Installed unstable poorly cooked ROM might cause EFS partition to be corrupted or missing. Which will make your Samsung Galaxy S3 fail to make voice call due to missing IMEI number. So better to make a backup of your Samsung Galaxy S3 EFS partition.


Verify EFS Backup

The easiest way to backup EFS ~ use EFS backup / restore tool like kTool by Hellcat. kTool will backup the whole EFS partition (including files read / write permission) for you with 1 click. And do verify EFS Backup after that. kTool will generate 2 files ~ efs.img and efs.tar.gz on sdcard. Make sure to keep another copy on PC or cloud storage.

Download HC-kTool at Google Play Store here.


  1. Hi jayce,

    i found file EFS here in may sgs2 what is the use of this files. And is there andproblem if i delete those ro my file?
    Many thanks again.

  2. Both CWM(v3.60) and HC-ktool are not working on my S3.

    CWM pop up a message – “This version of CWM Manager should be used with CF-Root v5.0 or newer. It appears you are runnig a different kernel. Various features have been disabled.”

    HC-ktool failed to locate efs.img and efs.tar.gz after I successfully backuped efs.img and run check.

    I did a OTA after I rooted(CF-Root 6.4) my S3. It seems that the new update is not supported by the CWM and HC-ktool. Where can I find the right CWM and HC-ktool ?

    My S3 base band was I9300XXLEF and now is I9300LG3. (Area – Taiwan)



  3. Hi Jayce,

    I have my new S3, and have rooted via CF v6.4 . I have attemted to unlock from Vodafone Spain using HC-kTool, and voodoo SIIISimunlock.apk I think all went well, but as of today I do not have another micro sim to check it out . . I travel to the UK soon and hope it will work. Is there any way to check without using a sim??

    Another question . I backed up my efs both before and after using voodoo (on my computer) can I now delete the old efs files and voodoo files sitting on my sdcard??

    Where do the “action” efs files reside (is it in /dev/block/platform/dw_mmc/by-name??

    As you can probably tell – bit of a newbie

  4. Hi,

    Im new to Samsung Android and rooting. Last night I rooted my new Telstra S3 GT-i9305t and now I cant get a network signal. Says my IMEA is “Unknown” when I check under About and where it usually has the mobile signal bar in the top of the screen I get a circle with a line through it.

    I dont have a backup of my EFS (found out later that this is a wise thing to do!!) and Ive searched all over the web for a fix.

    I even tried to install stock firmware from here ( which unrooted my phone but didnt fix the IMEI Unknown issue.

    Please can anyone help me to get my phone back to working order?



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