kern/153804: boot from zfs kernel.old recovery undocumented/impossible

[Andriy Gapon]

The following reply was made to PR kern/153804; it has been noted by GNATS.

From: Andriy Gapon <avg at FreeBSD.org>
To: Pan Tsu <inyaoo at gmail.com>, bug-followup at FreeBSD.org,
        Nick Sayer <nsayer at kfu.com>
Cc:  
Subject: Re: kern/153804: boot from zfs kernel.old recovery undocumented/impossible
Date: Thu, 26 May 2011 14:54:53 +0300

 on 25/05/2011 11:52 Pan Tsu said the following:
 > Andriy Gapon <avg at FreeBSD.org> writes:
 > 
 >> Try the following options:
 >>
 >> 1)
 >> unload
 >> set kernel=kernel.old
 >> boot
 >>
 >> 2)
 >> unload
 >> load /boot/kernel.old/kernel
 >> load -t /boot/zfs/zpool.cache /boot/zfs/zpool.cache
 > 
 > zpool_cache_type can be anything. loader(8) unlike grub2 doesn't enforce
 > type to be "/boot/zfs/zpool.cache".
 
 Yes, one can specify load -t anything /boot/zfs/zpool.cache and it will work.
 I was just on the safe side following what's done in /boot/defaults/loader.conf.
 
 >> boot
 > 
 > Whatever happened to just typing following?
 > 
 >   boot kernel.old
 > 
 > It assumes zpool.cache was already preloaded by failed attempt to boot
 > default kernel. No need to `unload' the kernel, `boot' replaces it.
 > 
 
 Yes, I think that this command is a more convenient form of doing #1 above.
 
 All in all, I qualify this as a pilot error.
 Supported convenience methods do the right thing automatically.  In the completely
 manual method a user should know what he is doing.  Perhaps it's worth mentioning
 somewhere that zpool.cache must be loaded, but I think that it's a common knowledge.
 
 -- 
 Andriy Gapon