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Date:      Tue, 21 Jul 2009 08:44:46 +1000
From:      Aristedes Maniatis <ari@ish.com.au>
To:        Kip Macy <kmacy@freebsd.org>
Cc:        freebsd-current@freebsd.org, Jurgen Weber <jurgen@ish.com.au>
Subject:   Re: Problematic upgrade from 7.2 to 8.0 with ZFS file system
Message-ID:  <4A64F35E.6070501@ish.com.au>
In-Reply-To: <3c1674c90907201501j42f29bfbl987419edf04b1a8b@mail.gmail.com>
References:  <4A5D4D25.3040908@ish.com.au> <3c1674c90907201501j42f29bfbl987419edf04b1a8b@mail.gmail.com>

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On 21/07/09 8:01 AM, Kip Macy wrote:
>> The other solution is to install userland BEFORE you reboot into the new
>> >  kernel, although that may cause its own set of problems. Whatever the final
>> >  solution, this needs to be clearly documented and ideally freebsd-update
>> >  needs to detect the problem and advise the user about what to do.
>
>
> Do to the large version jump (v6 ->  v13) the kernel interfaces aren't
> backward compatible with the tools. How do you think it could be most
> gracefully handled?

I honestly don't know how the right way to solve the problem, but here 
are some ideas:

* the kernel ABI *should* be compatible with userland tools at least one 
major version backward. I understand that this might now be impossible, 
but it is possible to bring back enough of the old ABI to allow for zfs 
to mount?

* freebsd-update could automatically detect this situation and install 
the new zfs userland at the same time as the new kernel

* lots of of clear documentation about what course of action a user 
should follow if they are performing a source update. Should the 
recommendation be changed to install userland *before* rebooting, and 
then immediately reboot before some of that userland explodes against 
the old kernel in memory?

The existing recommendation is based on the fact that the new kernel 
will continue to work after reboot with the old userland. If that 
assumption is not always true then the whole FreeBSD installation 
process needs rethinking.



Ari Maniatis



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