zfs: allow to mount root from a pool not in zpool.cache

[Matthew D. Fuller]

On Fri, Oct 05, 2012 at 08:38:49AM +0200 I heard the voice of
Pawel Jakub Dawidek, and lo! it spake thus:
> 
> In my opinion requiring no zpool.cache to import root pool and mount
> root file system is great idea and we should definiately do it.

As a user, I heartily agree.  I've setup a number of ZFS systems now,
generally by booting up a live CD/USB/existing install on an extra
drive, setting up and installing files, then unplugging the temp drive
and letting it come up.

So far, I haven't yet _ever_ had it actually boot right the first
time.  It keeps getting up to the root mount and failing.  I've always
had to plug the other drive back in and "squirrel around" with
zpool.cache until it works.  The last time, I believe it was because
during the setup I had one NIC plugged in, and the "real" system used
the other, so the hostid wound up different?  It's kinda like an
adventure game, but the replay value is a bit low   8-}



-- 
Matthew Fuller     (MF4839)   |  fullermd at over-yonder.net
Systems/Network Administrator |  http://www.over-yonder.net/~fullermd/
           On the Internet, nobody can hear you scream.