This is a duplicate of T7487 which has an open PR against is so I think this ticket should be closed.

There's now a PR for this: https://github.com/vyos/vyos-1x/pull/4969

In T3936#219798, @gmurphy42 wrote:

Just gonna bump this again. Would be great to see support for this as it would be super helpful for complex architecture-based netboot configurations.

A post from the forum showing a perfect example of the use case: https://forum.vyos.io/t/how-to-setup-vyos-to-let-it-support-netboot-xyz/14391/5

I have implemented this and created the following pull requests:-

Created PR here: https://github.com/vyos/vyos-1x/pull/4642

I'll follow this up on the forum as that is probably a better place for this discussion but I followed those instructions verbatim on a brand new virtual machine install with fresh up to date docker images and it fails in the exact same way every time. Are you running on an old machine you've had set up for a long time? It might have state in it that allows builds that's not present on fresh installs.

I have created a PR with a code change to resolve this bug with the "quick fix" solution: https://github.com/vyos/vyos-1x/pull/4527