[T-Mobile, Samsung Galaxy SIII] getsaf:
Can't speak to how any of the apps in the market do. This backup method has been used in Linux/Unix for drive / partition mirroring for as long as I've used Linux (mid to late 90's for me).

I think part of the issue is that we don't know how apps do their backups so it's tough to know if their backups are legit. Doing it yourself like this gives us first hand knowledge of what is being backed up and how. By all means, if you have an app that claims to backup efs try it. I'd trust dd over an app personally.

---------- Post added at 01:35 AM ---------- Previous post was at 01:03 AM ----------

So, a little more investigation shows that the IMEI folder in the efs partition doesn't contain much. Mine contains exactly 3 bytes, the letters 'TMB'. So, it's either not in the EFS or just not in the folder labeled IMEI (which seems like an obvious spot to place it).

There are other files in here, here's my full list of files. I'm really not sure where an IMEI would typically be stored (never needed to before) but I'll be looking for mine in some of the files I found here...

FYI, my IMEI is ok. I just hope to find some way to help out others or at least help find a legit backup solution.

Does anyone know if any of these files looks like a good place for an IMEI? Know how it's stored? ASCII, LE/BE-Binary? Tips on how to search besides grep?

shell@android:/efs # ls -lRa

.:
drwxrwxr-x root root 1969-12-31 19:00 .files
drwxrwxr-x system system 2011-12-31 19:02 FactoryApp
drwxr-xr-x radio radio 2012-06-17 13:48 bluetooth
drwxrwxr-x system system 2011-12-31 19:00 drm
drwxrwxr-x radio radio 2011-12-31 19:03 imei
-rw-r--r-- radio radio 880 2011-12-31 19:01 redata.bin
drwxrwxr-x root root 1969-12-31 19:00 sensors
drwxrwxr-x system system 1969-12-31 19:00 wifi
-rw-r--r-- radio radio 144 2012-06-17 13:48 wv.keys

./.files:
drwxrwxr-x media system 1969-12-31 19:00 .dm33
drwxrwxr-x media system 1969-12-31 19:00 .dx1
drwxrwxr-x media system 1969-12-31 19:00 .mp301

./.files/.dm33:

./.files/.dx1:

./.files/.mp301:

./FactoryApp:
-rwxr--r-- system system 3 2012-06-17 12:45 baro_delta
-rwxr--r-- system system 2 2012-06-17 13:48 factorymode
-rwxr-xr-x system radio 4 2011-12-31 19:00 fdata
-rwxr-xr-x system radio 0 2011-12-31 19:02 hist_nv
-rwxr--r-- system system 6 2012-06-17 12:45 hw_ver
-rwxr--r-- system system 2 2012-06-17 13:48 keystr
-rwxr--r-- system system 11 2012-06-17 13:48 serial_no
-rwxr-xr-x system radio 270 2011-12-31 19:02 test_nv

./bluetooth:
-rw-r--r-- radio radio 17 2012-06-17 13:48 bt_addr

./drm:
drwxrwxr-- system system 2011-12-31 19:00 dxhdcp2
drwxrwxr-- system system 2011-12-31 19:00 h2k
drwxrwxr-- system system 2011-12-31 19:00 playready
drwxrwxr-- system system 2012-06-17 13:48 widevine

./drm/dxhdcp2:
drwxrwxr-- system system 2011-12-31 19:00 acGSIRU1TX-2o-nJ69e1aFGgUxE_

./drm/dxhdcp2/acGSIRU1TX-2o-nJ69e1aFGgUxE_:
-rwx------ system system 1072 2011-12-31 19:00 etK7oituoft7bxrO5H7GIVuhEQM_
-rwx------ system system 1072 2011-12-31 19:00 zttE+GVYd9YzREzMHiKY-IlERZM_

./drm/h2k:
drwxrwxr-- system system 2011-12-31 19:00 8tjfX-7nJB21LtUUWIMbdlUfZTU_

./drm/h2k/8tjfX-7nJB21LtUUWIMbdlUfZTU_:
-rwx------ system system 1072 2011-12-31 19:00 HAv-sOqL1pMh2jiAzRoeKCzAmhE_
-rwx------ system system 1072 2011-12-31 19:00 SNbX8rtYWzaqdrnXa79HbAt5OFM_

./drm/playready:
-rwx------ system system 3 2011-12-31 19:00 00002.PRV
drwxrwxr-- system system 2011-12-31 19:00 EFPJyjNZ9nEurZknh1Fu2rEHxS8_
-rwx------ system system 2076 2011-12-31 19:00 bdevcert.dat
-rwx------ system system 5672 2011-12-31 19:00 devcert.dat
-rwx------ system system 233472 2011-12-31 19:00 license.hds

./drm/playready/EFPJyjNZ9nEurZknh1Fu2rEHxS8_:
-rwx------ system system 1072 2011-12-31 19:00 -lndchIc3h7lLcBHqLCVTRwsBQU_
-rwx------ system system 1072 2011-12-31 19:00 13FYUtLowgJQh+YoFynLFMn9Pvc_
-rwx------ system system 1072 2011-12-31 19:00 2a8EC7fiuOLWZ6xkJz2qV9BUyqY_
-rwx------ system system 1072 2011-12-31 19:00 39Xa-cFeuYfBSpC0hzzDgyz3Bss_
-rwx------ system system 1072 2011-12-31 19:00 39j-Wt07C-dAogUK9xbr3vf7xFY_
-rwx------ system system 1072 2011-12-31 19:00 AqEmxtFosQPPH-ASRTWrTN0zFwI_
-rwx------ system system 1072 2011-12-31 19:00 fil8fYE2kpyD+gNF9IULyWpJiMs_
-rwx------ system system 1072 2011-12-31 19:00 g2zzvmrUAAM9ik-uBWw9IdCij5w_
-rwx------ system system 1072 2011-12-31 19:00 mxrN+7RFB9miwfZrRU1xlWieu4M_
-rwx------ system system 1072 2011-12-31 19:00 oUtpSCeDR40uafRBmUR7mFYw+ik_
-rwx------ system system 1072 2011-12-31 19:00 sAp0dyXpZJo1C1wRx+RXzLXa6Kc_
-rwx------ system system 1072 2011-12-31 19:00 wHPCuFBMd5Z7-P4jMU--oBvQDz4_
-rwx------ system system 1072 2011-12-31 19:00 xmCXhhIu8UwnU13OCzfWzRXOFiI_

./drm/widevine:
drwxrwxr-- system system 2012-06-17 13:48 5dsokxEEDXgQhkN50bp-Z2K5InM_

./drm/widevine/5dsokxEEDXgQhkN50bp-Z2K5InM_:
-rwx------ system system 1072 2012-06-17 13:48 D3qpp0bxmJhbiZwIsCbXJ1434rc_
-rwx------ system system 1072 2012-06-17 13:48 RXFABDUxyT6Q+Zwx9ZhPGOq2Bq8_

./imei:
-rw-rw-rw- radio radio 3 2012-07-04 22:57 mps_code.dat

./sensors:

./wifi:
-rw-rw-r-- system radio 17 2011-12-31 19:00 .mac.info

---------- Post added at 02:27 AM ---------- Previous post was at 01:35 AM ----------

So, none of the other files seem to be of any use, *IF* the IMEI is in the EFS partition, it's in the redata.bin file. Unfortunately, I'm unable to descern what kind the file format is. Seems to be encrypted to me but it doesn't match any magic-number for 'file' and it doesn't show any patterns or indicators that I recognize to tell what's in the file.

I do see that it belongs to 'radio'

-rw-r--r-- radio radio 880 2011-12-31 19:01 redata.bin

If I were brave enough, I'd remove the file and reboot to see if my IMEI disappears, then copy it back. But who am I kidding I'm not that much of a gambler with a working $700 phone. I can tell you the MD5 of my redata.bin file is:

e01e0bd81749cb9f83a56cac6012c10b redata.bin

If this does contain information specific to each phone, then others MD5 will be different than mine. Can anyone else get the MD5 of their redata file? Better yet, can someone with a borked IMEI send me this file from their phone?

I'm on T-Mobile 16gb white.

on the terminal:

# su
# md5sum /efs/redata.bin