Stuck in fastboot mode


Sorry for my English, I’m French.

I recently bought a FP4 (thanks Santa) and I try to install /e/ OS on it. I succeed but I had a error message seemingly common on the forum : “The boot loader is unlocked and software integrity cannot be guaranted”. So I try to lock the boot loader using the command “fastboot flashing lock”.

It creates a huge warning also seemingly common :
I got the red alert : “your device is corrupted…”.

My phone restarted but I’m stuck in a Fastboot mode loop where I can’t go outside when I turn on my FP4.
I can lock ou unlock the fastboot, using commands on my computer, but I can’t go outside.

Can someone could help me please ?
Maybe the answer is somewhere on the forum but I can’t find it and a little bit depressed…

Regain your privacy! Adopt /e/ the unGoogled mobile OS and online servicesphone

Hi, @LG75 ,
Welcome here.

What build branch, dev or stable ?

Thanks @piero !
I’m sorry. I don’t understand. Maybe, you are talking about the way I install /e/. I used easy-installer and it goes well until the end.

I have this on my screen.

Your device’s bootloader seems to be locked… Did you activate OEM Unlock in the developer options before the installation?

Yes I did it. I follow all the instructions in easy-installer. Everything goes well.
At the end, I just had a yellow message about bootloader not lock. So I try to lock it but I made a mistake and had a red error message about my phone corrupted.

I follow the instruction to lock the bootloader :
It creates the critical error.

Easy-Installer = stable

Install /e/OS on a Fairphone FP4 - “FP4”

Fairphone - FP4 - FP4 - Documentation Suggestions

Apparently, I need you @AnotherElk after a quick discussion with Piero.

Can you help me to go out of the fastboot mode ?

Then you should try to install Fairphone’s stock Android again, as described here. After that you can reinstall /e/OS but the bootloader should remain unlocked. You can ignore the yellow message.

I don’t have a Fairphone 4, and I’m not completely in the loop regarding the locking of its bootloader, which seemed to be tricky at least for a while from what I read. So I’ll try to avoid possibly making matters worse with not enough knowledge before somebody more in the know can help.

Perhaps @ff2u can give some advice?

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Thanks. I prepare myself to follow the idea of Tux17 in case of. And then try later to install /e/ on my FP4.

Maybe @ff2u will have a better idea :slight_smile:

Last question : is it not a problem to let bootloader unlocked after reinstall /e/ ?

It is if someone malicious take your device in his hands.
Most supported devices can’t be relocked, only a few can.


Actually you didn’t do a mistake but it’s unfortunately a problem of the “anti rollback feature” implemented. You very probably had FPOS installed before with a newer security status date than /e/OS now. So this leads to the “phone corrupt” message on relocking the bootloader (and so activating anti rollback feature).
I hope that “OEM unlock” is still “enabled” (this should be the case with installing /e/OS). So did you try to go to fastboot mode and type fastboot flashing unlock there?

This will probably not work (to reinstall the OS) as this is not possible while bootloader is locked… (and btw I would not reinstall FPOS - as this will switch OEM lock to “disabled” and make it even more difficult…)

If you’re interested in all details then you might read the (lengthly) topic here:


To be a bit more detailed:

Yes, locking bootloader may help in this case. Your data is probably not directly in danger in this case (as data is encrypted). But someone could flash you malicious code (and so do anything with your device once you keep using it with a malicious OS.

FP4 supports it. But only if you flash an OS with a newer security status date than the OS installed before.

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Thanks a lot @ff2u ! My actions seem more clear now.

I try and I have now “DEVICE STATE - unlocked” on my fastboot mode. Is it a good news to find a solution ?
Is there a solution in the lengthily (indeed !) topic ?

That’s very good news.
Now you are at the point you were before locking the bootloader.
So your device should boot.

It depends. For some there was only the solution to send the device in (if OEM unlock was disabled and so the device was hard bricked). For others the solution was to unlock the device again and use it unlocked…

If you really want to have the bootloader locked, then you have to wait until the next /e/OS update. Then you’ll probably be able to successfully lock the bootloader. BUT this locking will do a “factory reset”. So you need a good backup then or have to setup all from scratch.
Before locking the bootloader please always check OEM unlock status! I’d never lock it if OEM unlock is disabled as this could lead to a bricked device. You can check OEM unlock status in developer options or via fastboot (fastboot flashing get_unlock_ability results in “1” for “OEM unlock” status “enabled”).


IMHO this message is a “warning” but no “error”. You’ll only see it when booting (what probably won’t happen too often) and you may get used to it. Still, as mentioned above, you’ve to decide for yourself if an unlocked bootloader is ok for you or not.

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For example, With locked bootloader, you can update /e/, but not upgrade.

At least an upgrade will for sure be possible with an unlocked bootloader. For some devices an OTA upgrade to a new major OS release is available or under development, so it might be possible for the FP4, too…

Oh I’m hapy to read that !
But I’m still stuck in the fastboot mode. No matter my choice between “Start/Restart Bootloader/Recovery mode/ Power off”, I always come back on that fastboot mode page.

Or maybe, if I understand correctly, I can relaunch the easy-installer because it’s unlock ?

Do you mean send it to FP and cost me 30€ ?

I tried and I got a “1”. Still goof news.
I understand the need to be at the same “level of update” before locking the bootloader. Is there a page on the forum or something else where I can be sure in the future ?

I read that unlock bootloader block some application, like banking. Is it right ? As a newbie, it’s hard to estimate the risk beyond this (like hacking).

Thanks again to all for answering all my questions ! This is really kind.

I find this subject on FP forum : Fairphone 4 "locked in fastboot mode" - #7 by hirnsushi - Fairphone 4 - Fairphone Community Forum

So I switch the slot thing from “a” to “b”, but I have no idea of the impact and what it did inside of my phone (if you can explain to me please).

But at least, I can go outside of the fastboot mode and now I have this on my screen, and no idea what to do (and I want to avoid to do something wrong).

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