The IMEI (International Mobile Equipment Identity) number of a smartphone is an essential piece of information. If your phone falls out of your pocket in an unknown place or if it gets stolen from public places, you need to provide…
If you are one of those who often tryout custom ROMs on your OnePlus One, you should take care of EFS data of your device, because EFS data contains all networks related things such as IMEI number, Wireless MAC address, baseband version, etc. Once it is lost, you will not be able to use your phone on any mobile network. Also, you cannot use Wi-Fi, Bluetooth, etc. Therefore, you should always make a backup of the EFS data before installing a custom ROM.
Every Android smartphone has EFS or NVRAM data, which contains all data related to the phone, such as IMEI number, Wireless MAC address, product code, baseband version, system ID and NV data. If it gets corrupt, you cannot use your phone with any mobile network as well as lose all the connectivity features of the phone such as Wi-Fi, Bluetooth, etc.
There is a plethora of custom ROMs out there for Samsung Galaxy devices, but before flashing any custom ROM, you should backup EFS partition on your Galaxy phone. EFS partition contains all data related to your phone’s IMEI, so if you accidentally wiped EFS partition while flashing a ROM, you will not be able to use your device with any mobile network. This is a common problem with all Samsung Galaxy devices.