IMEI

IMEI
WHAT IS?
The IMEI (International Mobile Equipment Identity) number is a unique set of 15 digits used on GSM phones to identify them. Because the SIM card is associated with the user and can be swapped from phone to phone, a method is needed to keep track of the hardware itself, and that's why the IMEI was developed. Math nerds will enjoy the way they are calculated - the first 14 digits are decided by the GSM association, and the final check digit is computed using what's called the Luhn Formula -> crazy base-8 math that mere mortals like most of us don't understand, nor want to understand. You can see the IMEI of your Android phone by looking in settings -> About phone if you're curious / on the box if you still have it / under the battery on the phone itself.
What is this number used for? That's the real question, isn't it. The IMEI is used for network control. It's not very common, but your mobile operator can block a phone based on it's IMEI in cases where it's been reported stolen or someone didn't pay the bill.
On a lighter note, Android apps can also use your IMEI number. The app will declare that it has access to your personal information, and the IMEI can be used to keep track of the device in a remote database. This sounds pretty scary, but it's an easy way (though not necessarily the best way) for app developers to keep a settings database online for your phone, in their app. Let's say you mark a bunch of favorites in a wallpaper app. Those favorites are kept in a small database file online, and when you reconnect to the app it reads your IMEI number to find your preferences. Not an ideal method, but it's easy.


androidlost.png
IF YOU LOSE OR MESS UP YOUR IMEI NUMBER, A PORTAL TO NETWORK HELL WILL OPEN AND CONSUME YOUR PHONE...
...causing to experience any of this:

1) Corrupt or incorrect (FAKE) IMEI number
2) No Network and Signal ( calls, sms and mobile Internet not working)
3) No base Band or Unknown Baseband
4) Sim card lock missing
5) Undermentioned appearing in red on your desktop after phone boots up normally
HW: Not Active
BOOT: SHW-M110S Vj04.1944
PDA:SHW-M110S Vj04.1944
Phone: M110S.VI27.0941.ST
6) Undermentioned appearing when you try to boot
E: failed to mount /efs (invalid argument)
E: check_selective_file:Can´t mount /efs
7) Undermentioned appearing when you try to boot
E: failed to mount /efs (invalid argument)
install_application_for_customer:Can´t mount /efs
copy application failed
8) Undermentioned appearing when you try to boot
E: failed to mount /efs (invalid argument)
E: multi_csc: Can´t mount /efs
Multi-csc applied failed
9) Undermentioned appearing when you try to boot
E: failed to mount /dev/block/stl3 or
E: failed to mount /dev/block/bml3 corrupted


HOW TO AVOID PROBLEMS?
You guessed it, the solution is to backup BEFORE flashing anything. Nandroid Backup will not cut it. The simplest way to do it is to use a Root Explorer -> locate EFS folder -> zip it and save to another location (i.e. sdcard, computer...)

Or you can do the backup with different apps (click on the image to get it):


EFS PRO

efspro.png



NITRALITY

nitrality.jpg


kTOOL

kTool.jpg



HAVEN`T MADE BACKUP BEFORE, I`M IN NETWORK HELL, WHAT CAN I DO?
If you were foolish enough not to listen the words of wisdom or read enough about this subject before, you`ve done yourself a stupid favor and some work. To get it back you will have to reflash stock firmware with Odin, root your phone and/or flash your fav custom ROM again.

In case you`re really, really unlucky and this did not solve your problem or you`re using fake IMEI and you would like to get the original one back try this:


Must have:

- SHIPPED ORIGINAL EFS FOLDER ON YOUR PHONE (even if it's messed up) FOR THIS METHOD TO POTENTIALLY WORK
- root
- root explorer for copying files to and from EFS folder
- Android SDK for the ADB tools or Terminal in your phone

Restore your phones firmware to its original PDA, Phone and CSC, root it with CF-Root, and then do procedure below! (credits vaskodogamagmail)

The IMEI is stored in ".nv_data" file in ORIGINAL SHIPPED EFS folder too, so you just have to do these:

1) make a copy of your EFS folder to your sdcard using root explorer and then make a backup of the folder to your computer [to have another copy if you had to format sd card sometime]
2) delete the EFS folder (BE SURE YOU HAVE BACKED IT UP IN A SAFE PLACE AS SAID IN STEP 1) from the root of your phone using root explorer.
3) reset the phone, after that, go to the root, and you can see that the EFS folder is still there, don't make any mistake, this EFS folder is new and generated by the android OS.
4) go to EFS folder using root explorer, and delete "nv_data.bin", "nv_data.bin.md5".
5) go to your backed up EFS folder on your sdcard, copy the "imei" folder to the EFS folder at the root of your phone, then again go to the backed up EFS folder at yout sdcard and copy the " .nv_data " file to your EFS folder at the root of your phone using root explorer, NOTE: the dot in first of nv_data is not a mistake, copy the ".nv_data" file.
6) make another copy of the ".nv_data" file in EFS folder in your phone, so you would have 2 copies of ".nv_data" in EFS folder
7) rename one of ".nv_data" files to "nv_data.bin" and another one to "nv_data.bin.bak"
8) at your PC open CMD at the ADB tool path, or run Terminal at your phone enter these commands:
adb shell (use this command of you use ADB, if you're using terminal, skip this line)
su (ALLOW THE MESSAGE TO COME AT YOUR PHONES DISPLAY BY SUPERUSER PROGRAM)
chown 1001:radio /efs/nv_data.bin
9) reset your phone... after that you should have your original IMEI. you can check your IMEI by dialing *#06#



by arawn
Aug 24, 2012