[Miscellaneous Android Development] kgoerbig:
Just as a back story. I was messing around with installing ROM images using SPflash, and I made a BIG mistake! I selected the Format + Download option. I had previously done a backup with TWRP onto microsd, so I thought no big deal. Well, as it turns out, without backing up a specific partition with TWRP you will lose the fingerprint option and stored fingerprints with any ROM you install (including Stock). I had the impression that Fingerprint/settings were stored in the system partition, they are not. I had to fork over $15 for an Umidigi engineer to send me restoration files that restored fingerprint. Let me explain how to avoid that, and backup everything and avoid forking over $15!

See

https://community.umidigi.com/forum.php?mod=viewthread&tid=16951&extra=&page=1

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This section assumes you have not installed TWRP and haven't disable encryption yet. This section of instructions will send phone back to factory defaults!

1. Install TWRP/boot into twrp

2. TWRP Swipe Format (type yes)

3. Install Disable-Force-Encryption-Treble.zip

https://drive.google.com/open?id=1QS8Ey4x5kNtKcosINe43DPopeaKoyxvq

For more in-depth instructions, go see _cab13_'s post:

https://xdaforums.com/android/development/umidigi-one-max-custom-rom-modding-t3942521

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4. Reboot again, select reboot recovery.

5. Now for backing up EVERYTHING IMPORTANT. Including fingerprint.

I suggest backing up everything that is checked in these pics.

TWRP backup options to select:

https://photos.app.goo.gl/g2G117VnZ2mDvk2YA

https://photos.app.goo.gl/WjXY1EPxu3jgVpat5

Important Partitions:

Other partitions that are "checked" in the pictures above are for precautionary measures, and really do not change the size of the backup much.

modem, nvram, nvdata (IMEI and wireless data partitions)

boot, system, data (For Android, installed apps, and OS data)

tee (Backs up your entire individual fingerprint encryption/settings). These are individual settings, and cannot be used on other One Max's.

Testing:

*I don't recommend this, unless you really know what you are doing, and are 100% certain you have backed up all needed components.*

To test this, I opened SPflash, clicked on the format tab, and selected "auto format" and "format whole flash".

[IMG="Format Flash"]https://blog.hovatek.com/bpyeki/uploads/2018/01/How-to-Format-a-Single-Partition-of-a-Mediatek-MTK-device-using-SP-Flash-Tool-5.jpg[/IMG]

This rendered my phone useless, and after the format, the phone would no longer power on. To solve this, I loaded the default firmware from the Umidigi site

https://community.umidigi.com/forum.php?mod=forumdisplay&fid=211

Changed the recovery image to the twrp image, and changed the boot partition to a previous magisk image I had made of the boot partition:

SPflash restore https://photos.app.goo.gl/EKamtvkmksx8As5Q7

Clicked Download > Connected the usb cable to OneMax > Plugged into the PC

At this point, SPflash starts loading all the images onto the device. After it finishes, reboot into Android. If you go into settings > system > about phone > Status > IMEI information

The IMEI's will be blank! No worries, if you backed up the partitions I screenshot above, you can boot into TWRP and recover the modem, nvram, nvdata, boot, system, data, & tee partitions. Once recovered, all your data, fingerprints, modem & IMEI data will be restored.

Hope this helps.