Unable to install update 3.A.0136 on rooted FP3

Help Fairphone 3
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I have been unable to apply software update 3.A.0136 on my Fairphone running the stock OS for quite a while now. The progress bar goes until about half, then the update screen displays “Installation problem” in red letters. I tried restarting the phone, or trying at a different time, fully charged, but it did not help. (It might be relevant that my phone is rooted and the bootloader is unlocked.)

I could not find a similar topic, nor anything useful on Google, anyone experienced something similar maybe? What could I try? If nothing else, is there a way to at least read the logs of the update so I can understand the error better?

Thanks in advance!

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I do not own a FP3, so this is just an educated guess. Before an OTA updated the checksums of the partitions that will be updated are verified and the update will fail if they do not match. Using magisk rooting changes those checksums.

The solution is to uninstall magisk from within the app, which fixes the checksums, apply the OTA update, verify that everything works, and finally root again.

There might be a more elegant solution for this phone, but this should work on most phones.

Good luck :slight_smile:

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I would image that’s it :frowning:

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Hmm, good suggestion! I uninstalled Magisk from the app (“restore images”), restarted my phone, tried applying the update, but it still failed.

Magisk shows the status as “Installed: N/A, Zygisk: No, Ramdisk: Yes”. Now my phone is completely un-rooted, right?

What’s also weird that I was able to do OTA updates before without any problems, when my phone was already rooted. Though IIRC Magisk changed a bit a while back, so that might have been a different situation.

Any other suggestions?

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Yes, restoring images and rebooting unroots your phone. Restoring images should fix the block verification, did you do any manual modifications to system partitions? Even remounting /system as rw could screw up block verification.

If that’s the case you will most likely have to fix it manually, better wait for someone with FP3 experience :sweat_smile:

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Well, not sure if that counts as an extra modification, but I enabled Zygisk 2-3 weeks ago (after MagiskHide was removed), is that relevant maybe?

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That should not make a difference, no. Did you maybe install any new root apps since the last OTA?

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What do you mean by a “root app”?

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Any app that you granted root permissions

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Ah. Hm, no, nothing new, I only use Termux and Aurora Store that need root access, but used those before the last update as well.

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Did you ever manually flash a partition? fastboot flash boot boot.img or something similar? Which steps did you follow to root your phone?

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I used TWRP for side-loading Magisk.

No, I don’t think so.

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Thanks for the pointers @CransNeighbour, I finally figured that there is something wrong with the checksums as you said, so I decided to restore the stock OS via a PC.

I was able to update the OS using a PC by reinstalling, without losing my user data, as described here: Unable to install August security update on FP3 - #25 by StevenHachel

After that, I rooted my phone again. This time (instead of TWRP) I used Magisk’s instructions for patching the boot.img and flashing, (and re-flashing the vbmeta image), will see whether that allows for proper OTA behaviour. Anyway, everything works properly now, and I have the latest security update as well. :slightly_smiling_face:

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