A lot can go wrong while fiddling with the software of phone, especially when you’ve full Super user access with an unlocked bootloader. Carelessly flashing the wrong Rom/Kernal/Modem can cause a softbrick and your device might not turn back on unless you’ve above average debugging skills or you send it to the hospital (service center).
To avoid such scenes it is recommended that you always take a full nandroid backup before you install anything new on your phone. Nandroid backup is basically the complete backup of your phone in a state that it was in before the backup, everything is restored to an exact state that it was in before backup. The apps, app settings, system settings, wallpapers or for that matter even the messages that you chose to leave unread will be restored in the exact same manner when you perform a full Nandroid backup and restore it.
This is not suitable if you’re shifting ROMs and want data to be carried over, and in such a scenario it is recommended to use Titanium backup. Nandroid backups are heavy and take a lot of time to be created, it’s not always required though. If you’re just flashing a new modem or something similar, the backup of EFS partition is just enough.
- Bootloader unlocked
- TWRP installed
- Battery charged to >60%
Here’s how to unlock bootloader and install TWRP on OnePlus 2
How to do a Nandroid Backup
- The first step is to boot the device to recovery, this is different for different models. It’s generally either a combination of Vol+ and power button or Vol- and power button. Google “Model name boot to recovery” for specific instructions on booting to recovery for your device.
- Once your in the recovery open the Backup page where you’ll find several options to backup which include Cache, System, Boot, Recovery, EFS, Data and a few other depending on the phone model.
- Make sure all the boxes are ticked.
- there’ll be a text box to enter the title for your backup on the top. The default name is generally the generic one with data and time, for simplicity you can add a suffix to the default name. For example 2017-02-6–pre-root or 2017-02-2–pre-lineageos
- Once the name is set and all the boxes are selected swipe the slider right to start the backup
- Do note that the backup can take several minutes to complete and will take up considerable amount of space on the device make sure you’ve enough juice in the battery and enough storage before starting the backup to avoid errors.
- After successful completion of backup you can choose to reboot the device or go back to install the rom of your choice.
Backing up EFS partition
EFS stands for “Encrypted file system” which is a folder in the Android directory containing the most important data of your phone. It has all the baseband version, IMEI, serial number and everything else pertaining to network and communication. It is essential to exercise caution while messing with this device and it’s mandatory to backup atleast this partition before you install any new rom in case you’re too lazy to take a full nandroid backup. This is rather useful while making smaller modifications to the device, like updating the Device modem to a newer version.
- Boot to recovery by holding either the Vol+/Vol- button and the power button. This combination varies from device to device, perform a Google search for the exact combination.
- In the main menu select the backup page to enter backup wizard
- Uncheck all the boxes except EFS/Modem.
- Enter a title suffix like EFS for easy future access.
- Swipe the slider right to complete the backup.
Restoring EFS or Nandroid backup
The procedure to restore either EFS or Nandroid backup is exactly the same. The restoration of Nandroid backup can take more time than you’d expect so as a precaution make sure the battery is charged to >60% and it is also recommended to leave the device plugged in to a power source throughout restoration. It should be noted that if the restoration is abruptly interrupted, it might corrupt the file system due to the sensitivity of the task being performed.
- Reboot to recovery by holding either the Vol+/Vol- and power up button based your device.
- From the main menu select restore to open the restore page.
- Select the backup that you want to restore by clicking on the name.
- Check all the boxes pertaining to System, Data etc…
- Swipe the slider to the right to start the restoration process.
- The restoration will take several minutes, make sure that it is not interrupted. Interruption of this process might turnout to be fatal and can brick you phone.
- If the recovery prompts you to install super user or root, choose do not install. It’s always recommended to manually flash the latest SuperSU package.
- Reboot device on successful restoration.
Note: Although the above guide is very easy to follow, do exercise caution while fiddling with the file system especially because the bootloader is unlocked and the device is most likely rooted.
PS: The screenshots show the battery to be only 12%, the image was taken for reference purpose only and performing a backup or restore with such low amount of juice is very risky and can result in a soft brick!