Using RELENG_8 to compile for older RELENG_x

[Roland Smith]

On Wed, Dec 16, 2009 at 03:18:17PM -0500, grarpamp wrote:

> I think I'll try unpacking 4.11's release tarballs into an empty
> jail, doing whatever else the install does and launching that. I'm
> guessing I should be able to compile/install world/kernel/release/apps
> in there. Assuming the running RELENG_8 parent kernel services don't
> cause issues. If it doesn't work I can always fall back to [a].

If I understand correctly, you want to use the jail to run a 4.11 userland on
an 8.x kernel? If you are not running GENERIC on the host, remember to include
the COMPAT_FREEBSD4..COMPAT_FREEBSD7 options in your kernel. You'll need that
to run 4.x binaries. Running older binaries is possible. But on the other
hand running a userland that is not in sync with the kernel not supported and
known to be able to cause trouble. See e.g. §24.7 of the Handbook.

It will be an interesting experiment at least. :-)

I'd probably try installing 4.11 on a old spare machine first.

> Yeah, you could consider it 'embedded' all right. Like deep in a
> dusty corner, driving some critical legacy shims that they forgot
> about in the migration plan, oops.

Oops indeed. Old+'dusty corner'+'critical' is not a good combination in my
experience. If the scenario also contains the element 'no backups', its time
to run for the hills. :-/

Roland
-- 
R.F.Smith                                   http://www.xs4all.nl/~rsmith/
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