Do you really need userdata.img and cache.img to unbrick?

During a Q&A session of our Mediatek Software Repairs training at our Whatsapp group, a participant asked a troubling question: “How can I get userdata and cache to unbrick this Android phone?”. This question sounds silly but it isn’t.

The Genesis

For you to really see the wisdom in this question, I’ll need to take you back in time. As far back as when MTK Droid tools was the bomb. You see, backups then didn’t contain userdata and cache, only core files like preloader.bin, lk.bin, recovery.img, boot.img, scatter.txt, secro.img, system.img and logo.bin.

It made no sense adding a few hundred MB to the rom size since userdata and cache are optional partitions. Once you flashed a backup but got stuck at boot animation, the fix would be to boot into recovery mode and do a factory reset (provided you’d flashed the right firmware).

The Question

What really are userdata and cache partitions? Their names say it all. Userdata contains app & user data while cache contains temporarily stored (cached) data. You could easily wipe these partitions and your device would be almost new. Try wiping /system or /boot if you’re feeling adventurous or overly excited and you will be humbled 🙂 .

The Catch

Some people had trouble wiping data and cache in recovery mode, like some Tecno M3 and L3 users. The barriers were the Encryption Unsuccessful and Mount /data errors. The fix for these was to boot into factory mode and clear emmc. The problem was that not all of these cases were able to enter factory mode or clear emmc; hence the need for userdata.img and cache.img to make such devices boot up.

The Present

With the advent of hardware boxes / dongles, you can get full Android stock roms containing userdata.img & cache.img but hardly ever need them due to advancements in Android. The fellow who’d asked the question about userdata and cache actually came across our Individual files project where userdata, cache and system aren’t uploaded individually (unlike files for other partitions).

He’d thought to save some data by downloading them separately instead of the full firmware. Its pointless uploading system.img as an individual file since it could make up as much as 90% of the rom’s size. Userdata and cache on the other hand are optional to flash. Wiping (factory reset) can easily sort both out whether or not you flash them.

The Conclusion

You shouldn’t need userdata.img or cache.img to unbrick your Mediatek Android device. In fact, flashing them sometimes requires that you do a factory reset to go beyond the boot animation screen. A factory reset would do to sort userdata / cache issues. Should you have trouble doing a factory reset or booting into recovery mode, you can use SP Flash tool to format userdata and cache.

Has flashing userdata and cache (.img or .bin) ever helped you unbrick an Android device?