No mater what you do with your OnePlus One, you always should backup the EFS folder and IMEI, always. We cannot stress it enough how important the EFS folder is. Android has a big community and the OnePlus One has many developers who create custom programs. You can install a custom recovery, flash a ROM or even a simple mod, but before doing any of the processes mentioned above, you should always make a backup of the EFS folder.
The EFS folder on your OnePlus One contains all the information that makes it possible for the device to receive information from the SIM card. If you flash a file and something happens to the EFS folder, the IMEI number goes unknown and the phone will be unable to make or receive phone calls, send text messages or connect to the internet.
Even though every flashing guide recommends to make a full backup of the EFS folder and IMEI number, OnePlus One users usually neglect it simply because there is no official and easy guide to do so.
Recently, user Paresh Kalinani has created a one-click tool which makes the process of saving EFS data very simple. It does not require any custom recoveries. Everything can be done from your PC. You only need to download ADB drivers and the tool.
- On your phone, go to Settings > Developer Options and enable USB Debugging. If you don’t see Developer Options on the settings menu, enable it (tutorial).
- Extract the zip file and connect your phone with ADB.
- Double click on “BACKUP EFS.bat”.
- Press any key on the computer and the tool will backup the EFS folder and the IMEI number. Two files will show up on the same folder: ‘modemst1.bin’ & ‘modemst2.bin’.
- To restore these files, simply click on ‘RESTORE EFS.bat’.
This is the simple way of backing up and restoring EFS & IMEI number on your OnePlus One using a one-click tool.