ZFS pool not working on boot

[Dan Nelson]

In the last episode (Sep 19), Axel said:
> Adam Jacob Muller <freebsd-current at adam.gs> writes:
> > On Sep 19, 2007, at 6:44 PM, Axel wrote:
> >> There is a file called /boot/zfs/zpool.cache that is kept in sync
> >> and loaded at boot time.
> >>
> >> If that's not there , e.g. by your /boot pointing to it , you're
> >> hosed.
> >
> > File is there, of note is that some of the prior reboots had been
> > "unintentional" reboots, so it is possible that that file was
> > corrupt, however, it does not seem correct for zfs to come up in a
> > state that shows drives as corrupted and/or unavailable. I believe I
> > have corrected the crashing issue, however it still does not seem
> > that this is the correct behavior.
> 
> If you have a working root outside of zfs I'd do the following:
> 
> 1) Rename the zpool.cache to something else to be safe
> 2) Reboot, make sure that /boot/zfs points to the right location,
>    and reimport the pools.
> 3) Should be fine from there on.
> 
> I had sort of the same issue, the zpool.cache isn't documented too
> well yet; I only stumbled over it by doing a "lsmod" at the loader
> prompt;it's one reason root can be on zfs before hostid is set. If
> you setup zfs and don't have the future /boot/zfs set right it won't
> work because the information gets lost. With / on zfs it's crucial to
> have /boot point to the actual UFS boot partition and not be in your
> zfs / somewhere, cause that gets ignored until it's mounted.
> 
> It's a good idea to keep the actual old UFS / directory around 
> although only /boot gets used in there if you mount / from zfs.

What I do is populate my UFS /.boot filesystem with /etc, /lib, /libexec,
/bin, and /sbin from my root filesystem, so if zfs fails to load it's
easy to recover.

-- 
	Dan Nelson
	dnelson at allantgroup.com