Sometimes when we are installing Android custom ROM and kernels, EFS folder screw. As a result of that phone will not boot or IMEI and serial numbers are missing. Furthermore, sometime we can see ‘E: unable to mount /efs or E: failed to mount /efs (Invalid argument) error message in a stock recovery as well as a custom recovery. For an instance CWM or TWRP.
This issue can fix by submitting your device to the Samsung service center. But if your device under the warranty, you can’t. Then you can’t claim the warranty. Now we can easily fix cannot mount efs folder issue without hassle.
In some situation when we see this issue, we can’t even boot the device. Therefore, we can’t enable USB debugging. Although after installing CyanogenMod (I have tested) or other custom ROM with a CWM recovery these ROM enable the USB debugging in the recovery mode, even if the user disabled it in the settings. If your device still not installed a custom ROM or recovery, first install a custom recovery using ODIN then install the AOSP ROM normally.
In order to follow my this tutorial, you should have an EFS folder backup as a .img format and as I mentioned above paragraph, device should install a custom recovery with a CM or any other AOSP ROM. Backup img file should in the internal memory or external micro SD card (not inside a folder). In case if your backup not in the internal memory you can now copy it to the micro SD card.
- IMG format backup EFS folder.
- Custom recovery (I have tested on CWM touch recovery ).
- Custom ROM (Used CM ROM)
- Latest SuperSU zip from here.
- ADB files zip in here.
How to fix Samsung Galaxy phone failed to mount efs (invalid argument) issue.
If you already installed a custom recovery and a ROM, you can start this tutorial
- Install a CWM recovery using PC ODIN.
- Copy the efs backup img file, ROM and SuperSU zip files to an external SD card.
- Boot into the recovery. If your device in a continuous bootlooop, no matter press and hold the recovery mode booting keys. (Different devices have different key combinations, most of the cases, it’s Home, Power and Volume Up keys)
- Install a custom ROM such as CyanogenMod. Recommend the CM ROM.
- Then install the SuperSU zip file.
- Once ROM installed, go back to the Clockwokmod main menu, now reboot the phone. (Yes, your device may give a bootloop, no matter just reboots)
- Connect your Samsung Galaxy phone, tablet to the computer via USB cable.
- Again boot into the custom recovery. (Each device has different key combinations to boot into the recovery).
- Uncompressed downloaded ADB + Fastboot zip file.
- Next in your computer go to the extracted ADB.exe file contain folder.
- Press and hold the shift key on the PC keyboard and same time right click on the ADB folder.
- Next context menu choose “Open command window here”.
- Then type adb devices. It will show ADB xxxxx recovery.
- Next type below command.
- Then type following command line.
(if your backup efs.img on internal memory)
(if your backup efs.img on external memory eg:- micro SD card)
- Next type following line and hit the enter key.
- Then, following command.
- Finally, this command line.
- That’s all. Now your phone should boot properly.