Hi,
I recently bought a FP4 with plans to install /e/ OS, so I applied the most recent software update and reached stock FP4.TP2U.C.0136. However, after unlocking the bootloader and installing the latest /e/ image via the web installer, the boot loader refused to boot the image. This is probably due to stock being at security patch level 2025-06-05 while the /e/ image was still at 2025-05-01. So I re-installed stock to get a working phone again.
Is it feasible to install FP4.TP2R.C.0132 (from How to manually install Android on your Fairphone) to revert the bootloader’s notion of “minimum installed patch level” to a date before 2025-05-01?
Would it be dangerous to re-lock the bootloader after this downgrade? What should I check before re-locking? I read that I should fastboot flashing get_unlock_ability before re-locking, but this will report 0 as stock has “OEM unlock” disabled, right?
After reverting to stock as described above would I also have to fastboot flashing lock_critical to get everything locked again and completely revert the phone to a safe state?
Kind regards
Ingolf
Hi,
Why did you do this as you wanted to install /e/OS. Would have been better to keep an old version and install /e/OS on top of that.
Correct.
I think just unlocking the bootloader again would also have resulted in a working phone.
I doubt that.
Definitely!
I’d just try this out. I’ve read here on the forum that directly after installing stock and before booting into userland it’s still “1” (but have never tried it out myself). But you should definitely check it before trying to relock!!! I’d strongly advice not to relock the bootloader as long as the result of get_unlock_ability is “0”!
Locking critical partitions is AFAIK not necessary.
You might still consider to keep the bootloader unlocked if you’re aware of what that means and accept it.
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Thank you, Volker, for your answers.
Why did you do this as you wanted to install /e/OS. Would have been better to keep an old version and install /e/OS on top of that.
That’s definitively right. In fact, I did not choose that particular release of FPOS explicitly but followed the advice in the /e/ Web Installer to update the phone to the latest software; I updated via the normal OTA method and ended up with that FPOS release.
I think just unlocking the bootloader again would also have resulted in a working phone.
I’m not that certain that the bootloader had actually been locked as a final step of the Web Installation: I’d expect that flashing a different OS would have reverted “OEM unlock” to “disabled”, right? (I did not check, though.) But then, I would not have had a chance to solve the situation at all… So maybe the phone did not boot after the /e/ installation for completely different reason.
Locking critical partitions is AFAIK not necessary.
You might still consider to keep the bootloader unlocked if you’re aware of what that means and accept it.
Do you have a pointer to more information on the consequences of unlocked critical partitions?
Cheers
Ingolf
Ok, I see. Sometimes documenting does not reflect my opinion…
Yes, maybe. The question is if the web installer proposed a relocking of the bootloader and you accepted it (you always have to acknowledge this step manually on the screen). And if you did an unlocking again before installing stock (installation would be impossible without unlocking). If you didn’t lock/unlock then yes, maybe there was something else wrong with the /e/OS installation.
Sorry don’t have an expicit source at hand. Maybe you read a bit through the forum like using e.g. this search:
https://forum.fairphone.com/search?context=topic&context_id=120753&q=Unlock_critical&skip_context=true
Apart from that:
If you use fastboot flashing lock then it’s impossible to flash partitions. So IMHO no need to additionally lock critical partitions.
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Hi, Volker,
after the Web Installer completed, I did not confirm re-locking. Neither did I have to unlock before installing stock FPOS.
However, fastboot flashing get_unlock_ability now (after reverting to stock FPOS) reports 0, but I cannot set it to 1 again via developer settings as the switch is greyed out (“already unlocked”). Any idea to get it back to 1 without having to lock first (and risk bricking)?
Cheers
Ingolf
I asked to quickly: maybe this post does the trick…
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Yes, probably.
That’s what I meant with
from above.
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Hi, I know i’m coming in after the battle and your situation is solved.
I just wandered in and wanted to add some context about your quote here.
When bootloader is unlocked, it does not check the SPL. It’s only relevant with locked bootloader or locking bootloader.
So the reason why it didn’t work in the first place cannot be SPL related since you confirmed not having locked it again.
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