Ok, sometimes after some kind of flashing error/corruption, you end up with your Samsung S4 mini LTE (GT-i9195) returning error E:failed to mount /efs (Invalid argument) in various recovery tool (TWRP and others).
If you check your /efs with a root level explorer, you will find out the folder is empty. Technically this cause my phone to : loose bluetooth pairing after turning it off or turning off bluetooth stack. Also cannot install Lollipop, stuck on the loop boot 🙁 with Cyanogenmod or other updates.
Here is the fix for it :
– Flash TWRP recovery and root your device using recovery method by installing UPDATE-SuperSU-vX.XX.zip file.
– Install ADB on your computer.
– Boot your device into recovery mode (Vol Up+Home+Power).
– Connect your device to PC via USB cable wait until windows update the driver.
– In the recovery mode choose “Mount /System”
– Open ADB command window and type the following command (from windows command line, from the folder ADB is installed into):
mount -w -t ext4 /dev/block/mmcblk0p10
These instructions are quite similar to what you find around on Internet with S3, however here please note that the block is the N°10, different from the instructions you find googlig around. At this stage the phone should reboot itself.
If you encounter some « can’t mount /fstab » error, this is because you have NOT applied correctly the root UPDATE-Super-SU patch on the device.
By following the above command, it will create a generic EFS files on your device. Your IMEI number will NOT be changed or reset, as this is stored in a different place on a Samsung GT-i9195 (on the p11 and p12 blocks apparently).
Reboot, and voilà you should not hit this /efs folder issue anymore, and if you browse the /efs folder, you should now see something with folders named « drm », « imei » « lost+found » and « wifi ».