Error in Common Ubiquiti Procedures for XM AirMax devices?

Russell Senior russell at
Mon Nov 8 21:49:19 PST 2021

On Sun, Nov 7, 2021 at 5:07 PM Joe Ayers <joe at> wrote:
> Openwrt Github commit notes, Forum posts, and Documentation, refer to:
> "The mtd partitions layout for XM-type devices changed from AirOS v5.5
> to AirOS v5.6. Before installing OpenWrt, downgrade first to AirOS
> 5.5."
> reference:
> While the documentation is a path to succeed loading openwrt firmware,
> this commit fixed the soft-brick issue (soft-brick meaning tftp
> recovery with serial cable is possible):

I went looking and found that this commit is in all releases starting
with 17.01.x, but not in v15.05.1

> It is a key message, that openwrt firmware after this commit, will no
> longer soft-brick the device, not communicated.
> The key misunderstanding is around the root cause due to Ubiquiti
> tightening up uboot to further check partition sizes.   The root cause
> was identified as a bad openwrt size definition that older versions of
> uboot accepted, without end user awareness.
> The reason I raise this issue is due to users in the
> https// community struggling to downgrade to AirOX
> v5.5, and we spend time working with them only to do tftp
> "hold-reset-button" firmware loads to succeed as quickest path.
> Note, however, there are still issues where newer Uboot versions
> expect images to have particular naming conventions, which are also
> addressed in later fixes:

This one is in releases starting with v19.07.x, but not in v18.06.x and earlier.

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