I recently picked up a Xiaomi Mi MIX 3 & was able to unlock the bootloader after the 72 hour waiting period. That wasn’t a problem, however getting TWRP up & running was where I had a problem.

For some reason, whenever I would flash TWRP, but device was stuck in a fastboot loop — could not reboot out of it, boot the TWRP image, or any other method of exiting fastboot. I finally got TWRP working properly after flashing perseus_global_images_9.5.17_20190517.0000.00_9.0 _global_134d3070e5.tgz. I tried flashing one of the China ROM’s, & that was of no help.

Since this was turning out to be nothing close to simple like other devices, I was then running into an issue flashing NanoDroid after my ROM. That one seemed to be related to the /system partition not being found. It looks like my partition was instead mounted as /system_root, but the NanoDroid install script was looking for /system. Managed to fix that as well:

Results of mount:

…
/dev/block/sde48 on /system_root type ext4 (rw,seclabel,relatime,block_validity,delalloc,barrier,user_xattr)
…

Remount /system_root as /system:

perseus:/ # mount -o bind /system_root/system /system

Taking a look at NanoDroid-20.8.91.20190525.zip\CommonInstaller: Lines 248-252:

if [ -f /system/init.rc ]; then
mkdir /system_root 2>/dev/null
mount –move /system /system_root
mount -o bind /system_root/system /system
fi

Once NanoDroid was working, I then needed to double check how to restore my backed up Signal messages: Signal: Backup & Restore Messages.

Tags: Android, Custom ROM, Signal