Prevent brick fp5 eOS setup, instructions unclear

/e/OS Devices Fairphone
,
1

Hi everyone!

Just received my FP5 back from repair because last time i tried to install eOS i bricked my phone. So this time i want to be absolutley sure.

Im trying to install eOS on my FP5 using this guide.

Currently i have:

  • android security update 5 dec 2025
  • OEM unlocking enabled
  • USB debugging enabled

The latest version of eOS is:

THUS NOTE: SECURITY PATCH ANDROID > SECURITY PATCH eOS

Instructions are unclear:

  • Rollback protection errors trigger if you install an update whose version number is LESS than the rollback index’s value stored on device.
  • Rollback protection errors are FATAL when the bootloader is LOCKED .
  • Rollback protection errors are IGNORED when the bootloader is UNLOCKED .

My queston: Since i have UNLOCKED the boorloader because ‘OEM unlocking’ is enabled in developer options, I assume that i can still install eOS? I am assuming i can install i because from bullet 1: ROLLBACK PROTECTION ERRORS ARE TRIGGERED
BUT
bullet 2: ROLLBACK PROTECTION ERRORS ARE IGNORED ?

So the errors are triggered but they are IGNORED instead of being FATAL (=BRICKED) ?

Thank you!

Kind regards,

Johan

[HELP] I cannot manage to install e/os in my android FP6
2

So you realise that you describe a rollback sitiuation.

Start point 5-12-2025
Proposed 1-12 -2025 :red_exclamation_mark:

Ignored refers to the fact that you can install this with the roll-back hazard but you must not lock – risk of bricking.

In other words

Install unlocked: ROLLBACK PROTECTION ERRORS ARE IGNORED (the “error” [1] exists but is ignored)

If you lock this proposed /e/OS build: ROLLBACK PROTECTION ERRORS ARE TRIGGERED and we are told the phone may be bricked.

  • Never go back.

[1] The “error” in Android terms is that the Android environment is forced back against Android rules and thus by_the_rules lacks full integrity.

[HELP] I cannot manage to install e/os in my android FP6
3

Okay! yes so i am safe to proceed. am i right that i can lcok the bootloader again if the security pach of eOS becomes higher as 5 dec 2025?

4

The next likely /e/OS Android SPL expected to be 01-01-2026 with e-3.4 will be ok to lock (providing that SPL is confirmed at release, ofc).

5

thank you for your help!

1 Like
6

If you want to be sure before locking you can use these instructions. It helped me to decide whether it was ok to lock a Pixel 7. I’ve put it in a note on my phone, I guess it originated from Piero.

with the device in bootloader mode, check bootloader status by running :

fastboot oem device-info

fastboot flashing get_unlock_ability

if the return is 0

DON’T TRY TO RELOCK (wait untill an /e/OS update)

if the return is 1 → you can relock

fastboot flashing lock_critical

fastboot flashing lock

7

This sequence of commands does not query the Critical Rollback Index.

This sequence of commands definitely does not replace the already outlined method.

Why would I query get_unlock_ability when considering Lock Ability?

It is unfortunate that this idea is being constantly repeated adding to the confusion for users as the OP.

This sequence of commands has been used the check only “device state” in the case of users returning to lock “late”, after the known catch-up version has been installed.

This post, Installed 3.0.2 official and tried to lock bootloader - #6 by olli0371 is, I believe, an example of the appropriate use of the technique.