Possible reasons for hard-brick? ('fastboot flash' vs. 'fastboot flash boot' ?)

I had two equal FP3+ devices, the first I’m happily using with LineageOS + microG, the second I had tried to set up for someone else in exactly the same manner, but got it hard-bricked, result similar to I didn't think you could brick a phone this thoroughly

Before going through the same procedure again, I’d like to identify which step was most likely to cause things to go south.

In my thinking the no.1 candidate would be the command to flash the LineageOS recovery image:

Elsewhere I read that someone said they would NEVER use flash and boot in the same command. Hence my questions:

  • Are there any reasons to actually flash the recovery image saying fastboot flash boot?
  • Could a failed fastboot flash boot indeed cause things to go wrong beyond repair?

Next I could imagine that one of the recovery images was simply broken:

  • lineage-19.1-20220802-microG-FP3-recovery.img - this worked on phone #1
  • lineage-19.1-20220820-microG-FP3-recovery.img - used on phone #2 this never let me boot into recovery

Lastly: One of the last steps in trying to work with phone #2 was go back to square one using FP3(+). Install Fairphone OS offline. Half-way during this process I got an error so the flashing aborted. I could still repeat it from a different computer from where it seemed to succeed, but only to enter a boot loop, that could only be terminated by pulling the USB cable, from whereon the device was dead as stone. Question here: Could a “weak” USB connection cause severe failure during flashing? Reasons I can think of:

  • problematic cable (mine was quite long)?
  • weak USB-hub?
  • conflict between connection to phone and connection to external HD holding the image, where both are USB connections, i.e, could these two connections possibly conflict at the USB level?

If HW details of connections are critical, how can I find out in advance if my setup is safe?

Maybe some answers will help improving installation guides by alerting people to the various risks?

Its about TWRP however assume could help?

So I think it should be fixable or cant you boot to fastboot at the moment?


In general, yes. It depends on how the recovery in question works.
It could work by just booting it, it could work by flashing it.

The alternative TWRP recovery @yvmuell mentioned above on the Fairphone 3 works by just booting it, installing works via a script, flashing it to the boot partition doesn’t work.

The LineageOS instructions flash the LineageOS recovery to boot. I would suppose the LineageOS powers that be would know how to deal with their own recovery. (I don’t have experience with this recovery.)

I don’t think so.
Even if you flash the boot partition with something that doesn’t boot, you are still left with fastboot mode to repair the damage by flashing a working boot partition image e.g. from the stock Fairphone OS install files.
(The TWRP install instructions for instance say as much, also cited in the post above, so it’s a procedure which should still work.)

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Else maybe this can help, although I didnt read in detail,

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That device is dead as stone. Literally shows no reaction to whatever you might do to it. And in fact I don’t have it anymore - so my questions are about potentially installing LOS on a new phone.

Here’s one more detail from my transcript of that session: I actually made three attempts to flash the recovery image:

$ fastboot flash boot lineage-19.1-20220820-microG-FP3-recovery.img 
target reported max download size of 534772736 bytes
sending 'boot_b' (65536 KB)...
OKAY [  2.327s]
writing 'boot_b'...
OKAY [  0.629s]
finished. total time: 2.955s

Looked good, but never entered recovery. I thought: maybe it’s that specific recovery image?

$ fastboot flash boot lineage-19.1-20220802-microG-FP3-recovery.img 
target reported max download size of 534772736 bytes
sending 'boot' (65536 KB)...
OKAY [  7.898s]
writing 'boot'...
OKAY [  0.650s]
finished. total time: 8.548s

This is the image that had previously worked on my 1st phone. But here: no recovery.

$ fastboot flash boot lineage-19.1-20220802-microG-FP3-recovery.img 
target reported max download size of 534772736 bytes
sending 'boot' (65536 KB)...
OKAY [  2.357s]
writing 'boot'...
FAILED (remote: partition table doesn't exist)
finished. total time: 2.370s

Same image, just flashed once more (stupid, for lack of other ideas). Obviously something broke right here, not having a partition table was the thing that made me want to go back to square one.

Does anyone have an idea, why the first command sent to ‘boot_b’ while subsequent commands sent to ‘boot’? I didn’t specify this on the command line.

Edit: Unfortunately my transcript doesn’t prove I used the same fastboot version in all commands. I do have an old version installed by Ubuntu, but I think I used this throughout that session: “fastboot version 33.0.3-8952118”.

After the device got replaced, I started anew, this time carefully following ✏ FP3/FP3+: Complete guide for installing LineageOS

Because last time things went south (assumeably) after issuing
fastboot flash boot <img>
I opted for the variant without flash. That command answered

Sending 'boot.img' (65536 KB)                      OKAY [  2.106s]
Booting                                            OKAY [ 13.808s]
Finished. Total time: 18.006s

The guide states “Now, your Fairphone should boot into the recovery.”, but it doesn’t. Instead it boots normally, i.e., I’m unable to get in that recovery menu.

Again I tried different recovery images (feeling safe about this without flash), including one that previously (in August) worked just fine. The recent img I used is https://download.lineage.microg.org/FP3/lineage-19.1-20221016-microG-FP3-recovery.img

What could be the reason why booting into recovery no longer works? Apparently several folks had been successful using that guide.

So when you try to jut boot into the LOS recovery it might not work. I think its best to follow the official LOS instructions as the forum guide might not be up to date anymore

Thanks, maybe, but I’m scared by my previous experience when flashing to boot caused FAILED (remote: partition table doesn't exist) with the final result of a hard-brick.

To close the loop: I succeeded to install LOS+microG on another FP3+ with images from 20221201 (recovery) and 20221204 (zip). :slightly_smiling_face: (score is now: 2 success - 1 brick).

Here are some of the things I learned / did not learn on the way:

Not working:

  • fastboot boot <img> without flash consistently triggers a normal boot, so it doesn’t help on the FP3+. Tried both the plain LOS and LOS+microG variants of the recovery image.

Working (based on https://www.reddit.com/r/LineageOS/comments/n0k6sn/comment/h8ygk41/?utm_source=share&utm_medium=web2x&context=3):

  • detect active slot (when device is in the bootloader):
    • fastboot getvar slot-active:a
    • fastboot getvar slot-active:b
  • flash depending on the output from above, e.g.:
    • fastboot flash boot_b <recovery_img>

No answer found:

  • Some posts suggested fastboot flash:raw boot_b <img> (e.g. Unable to boot into recovery - #17 by Nicoolas), but I found no suitable description of the difference flash vs. flash:raw.
  • I’m also not sure if flashing to a specific slot is needed, rather than just saying boot.
  • What exactly caused the procedure to fail on the previous device?
  • The recovery image for LOS+microG still has no sha256 to verify against.
  • One guide suggested the command fastboot boot recovery <img> but I couldn’t find any confirmation that this syntax is even accepted.

Wiki update?

  • I guess ✏ FP3/FP3+: Complete guide for installing LineageOS should be updated (that’s where I read about the not-working fastboot boot variant).
    • I’m not confident to directly edit the wiki
    • its meta discussion is closed, so I can’t reply there.
    • what would be the normal process in this case?
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I added at least a warning to the wiki, so that people always read the official instructions as well.
However I would say there is no normal process when you find errors you can correct when you have the trust level

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