The primary storage module on Android powered devices is divided into several partitions. For aftermarket development, the Android modding community primarily deals with a handful of partitions, such as “/system”, “/recovery”, “/cache” etc. OEMs, on the other hand, often use less well-known partitions to store interesting parameters, like the lock/unlock state of the bootloader. One such partition is “/persist”, which usually contains calibration data of internal sensors and in some cases, unique identifiers like the MAC address of the Wi-Fi chip.
Due to its uniqueness, one can’t simply fix a broken persist partition by restoring a generic dump. In a similar manner, it is virtually impossible to properly rewrite the contents of “persist” even after a full firmware flash. This is why the owners of the OnePlus 8 Pro are having a hard time fixing a fingerprint enrollment bug related to a corrupt persist partition.
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The exact reason behind the corruption hasn’t been pinpointed yet. We know that the fingerprint sensor on the OnePlus 8 Pro might stop working under some particular scenarios (like after flashing a different regional firmware). The anomaly with fingerprint enrollment can be fixed after flashing a known-working dump of the persist partition from your very unit. Not all end users are expected to do so, thus the solution isn’t really feasible.
Fortunately, XDA Senior Member antnyhills has found a fairly generic way to fix a corrupt persist partition on the OnePlus 8 Pro. The idea is to extract the existing fingerprint calibration data from the target device with a broken persist partition and restore it on top of a cleaned persist. Given that you have root access on your OnePlus 8 Pro, the following command from a terminal emulator or ADB shell with root privilege should create a 1:1 backup of the persist partition.
dd if=/dev/block/bootdevice/by-name/persist of=/sdcard/persist.imgThe backup part is crucial, so don’t misplace the dump you created. We recommend making an off-device backup of the partition image. You can’t use the partition image from another user.
After backing up the partition, low-level EDL flashing has to be performed on the OnePlus 8 Pro to ensure that there is no firmware mismatch. At this point, the user should unlock the built in “Factory Mode” on the device and try to recalibrate the fingerprint sensor. The test is expected to fail, which is not a big deal anymore. All you need to do is restore the previously backed-up calibration data of the fingerprint scanner. If everything worked out correctly, you should be able to go into settings and add your fingerprints.
In case you find all the steps described in the above thread difficult, here’s a step-by-step video guide created by antnyhills to make things easier.
Have you faced any fingerprint enrollment glitches on your OnePlus 8 Pro? Let us know in the comments below!
The post How to fix fingerprint enrollment issues caused by broken persist partition on the OnePlus 8 Pro appeared first on xda-developers.
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