kernel HEAD && userland 7.0-REL?

[Alexander Sack]

On Sun, Jul 6, 2008 at 7:43 AM, Robert Watson <rwatson at freebsd.org> wrote:
>
> On Fri, 4 Jul 2008, Matthias Apitz wrote:
>
>> I'm running a RELENG_7 kernel and a userland as 7.0-REL on one of my
>> laptops; I've been asked to check if a given driver problem in RELENG_7 is
>> as well with HEAD... can I update the kernel to HEAD and let the userland
>> (and all my compiled ports) as 7.0-REL; I know that this is not the
>> intention, but it would cost me a lot of work if I should compile as well
>> ~200 ports....
>
> As a general rule, running old userspace on a new kernel works pretty well,
> but you should expect certain types of things to not work -- for example,
> monitoring tools that expect the kernel layout of data structures to be
> unchanged.  Within a particular -STABLE branch this is a bit less volatile,
> but as you go from, say, 6-STABLE to a 7-STABLE kernel, the chances that
> some of the more obscure options to netstat, etc, will not work are pretty
> high. Likewise, be careful to disable any third-party kernel modules that
> may require recompiling but aren't caught by the base system build, or
> you'll get a nasty surprise when they panic. :-)

Robert, really good point.  I ran into this exact problem not so long
ago (third-party driver not supporting newer kernels, chaos ensued).
I also think Mike's nextboot suggestion is one I (and others) should
pay attention too.  I tend to just install my test kernel blindly and
if it fails, reboot and interrupt the boot, etc. - I will use nextboot
for sure!

-aps