U6+ Firmware downgrade failures

Talk about Documentation
1

I am attempting to downgrade the firmware of two U6+ but it is failing to do so on both.
It is my understanding I need to downgrade to 6.6.55 official firmware before proceeding with openwrt install, they ship with 6.6.71
However, I first attempt tftp process and the AP ignores the put.
Then I attempted the method of SCP the bin renamed to fwupdate.bin to the /tmp/ folder and run syswrapper.sh upgrade2 &
However, this gives the error: Invalid version 'BZ.MT7981.v6.6.55+15189.231127.1104'
I then put on on the network and ran upgrade command with the link to the 6.6.55 firmware bin and received the same invalid version error.
I am 100% certain it is a U6+ and I am using u6+ firmware files.

I seem to recall last time having to do something in SSH to “unlock” the emmc for flashing before doing the downgrade but I cannot find any information on this, and it could be a different step, I’m not sure.

2

You have to reset the device conf when you are at x.y.lowest version to permit next downgrade.

3

they are both fresh from the box though. I issued syswrapper.sh restore-default & set-default
but same issue when trying to downgrade.

4

This might be a skill issue, I never tried ignoring the problem.
I updated the firmware to 6.7.23 to test and could not proceed with the downgrade from there.
however I simply ignored the firmware requirement, and proceeded to follow the installation guide, and it completed without errors.
the hardware is now running openwrt fine.

I suppose you can simply install from firmware 6.7.23 now without having to install 6.6.55.

1 Like
5

I moved to documentation area so that device page

Gets updated with aditional version.

6

thank you, and I can confirm it works on 6.6.71 as well. I just did the other one.
ftr I am flashing version OpenWrt 23.05.3 (r23809-234f1a2efa)
Not sure if it matters.

I know for sure in the past it wouldnt just work like this, about a year ago. something must have improved.

7

This is a misunderstanding. That's just the stock version I used for testing the OpenWrt install procedure when I added support for the device. I don't have the spare time or a spare U6+ device to test the install procedure every time Ubiquiti updates their firmware.

As you've experienced, the OpenWrt install procedure works on later versions. What you did here is the suggested approach.