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/efs folder backup

Discussion in 'Android Devices' started by Hawker, Sep 29, 2011.

  1. Hawker

    Hawker Well-Known Member
    Thread Starter

    Aug 2, 2011
    There is a mod for Revolution that allows you to make a backup of the /efs folder, which from what I gather is a very sensitive folder containing your phone's IMEI, mac address and much more. If this gets corrupt then your basically screwed. On top of this, the permissions of everything in this folder are critical with regards to rwx (chmod) group (chgrp) and ownership (chown). The Revolution mod (although I've not tried it out as yet) should apparently do all this for you. Have anyone on you on Revolution downloaded this mod yet?

    Firstly, for those not on Revolution, how do you back this folder up? For such a critical folder, backing this up does not seem to be particularly easy as you need to install a terminal emulator to log into your device, then do a manual backup. It seems that backups are performed by a device dump (dd) or the tar command. Strangely, I've not seen anyone use the cpio command to do this, so I was wondering if this command perhaps is not on android linux? Reason I ask is that cpio retains permissions much better than the tar command, so it would make sense to use this.

    Secondly, what are the symptoms your device would show if this folder was corrupted and needed to be restored? If such a critical folder was shafted, could it even be booted into recovery mode in the first place in order to restore the backup?

    How to back up your /efs folder


  2. Slug

    Slug Check six!

    Aug 1, 2009
    Mobile phone retail
    Inverness, UK
    MoDaCo ROMs do it automatically on installation via a startup script.

    I'm not sure tbh, but I expect the symtoms would be pretty drastic. :eek:

    I expect so, or into download mode (bootloader?), as afaict none of the folder contents are crucial to the OS. It's probably something I should read up on though, just in case Murphy strikes.

    How to back up your /efs folder[/QUOTE]
  3. Ageless Stranger

    Ageless Stranger Well-Known Member

    Dec 2, 2008
    Senior software developer
    Symptoms include but are not limited to: Missing or incorrect IEMI number and inability to connect to the cellular network. Your phone will still boot, you can still get in to recovery etc. If this directory is shafted, it can always be backed up by using a terminal emulator or ADB.

    I would tar zip the folder as that would preserve the rw and ownership flags.

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