Building 4.x releases on 5.x and 6.x

[Colin Percival]

Maxim Sobolev wrote:
> Does anybody knows if subject is possible? I guess that it is not due to 
> usage of vn(4) in the release building process, has anybody any insights 
> about actual state of things and/or another potential problems in mind. 
> If the only problem is vn(4) vs. md(4), I think it can be solved quite 
> easily, while providing a good way to avoid having separate test 
> machines for oldest branches.

I'm fairly certain that this is possible; certainly what I do on my FreeBSD
Update buildbox (building 4.x worlds and kernels inside jails while running
a 5.x kernel) is pretty much equivalent.

One problem you may encounter involves /dev -- you'll need to mount a devfs
inside the 4.x chroot rather than trying to MAKEDEV everything.  I'm not
sure if the `make release` code handles this.

Colin Percival