Re: [HEADSUP] zfs root pool mounting

On Fri, Nov 30, 2012 at 08:51:48AM +0200, Daniel Braniss wrote:
> > 
> > Recently some changes were made to how a root pool is opened for root filesystem
> > mounting.  Previously the root pool had to be present in zpool.cache.  Now it is
> > automatically discovered by probing available GEOM providers.
> > The new scheme is believed to be more flexible.  For example, it allows to prepare
> > a new root pool at one system, then export it and then boot from it on a new
> > system without doing any extra/magical steps with zpool.cache.  It could also be
> > convenient after zpool split and in some other situations.
> > 
> > The change was introduced via multiple commits, the latest relevant revision in
> > head is r243502.  The changes are partially MFC-ed, the remaining parts are
> > scheduled to be MFC-ed soon.
> > 
> > I have received a report that the change caused a problem with booting on at least
> > one system.  The problem has been identified as an issue in local environment and
> > has been fixed.  Please read on to see if you might be affected when you upgrade,
> > so that you can avoid any unnecessary surprises.
> > 
> > You might be affected if you ever had a pool named the same as your current root
> > pool.  And you still have any disks connected to your system that belonged to that
> > pool (in whole or via some partitions).  And that pool was never properly
> > destroyed using zpool destroy, but merely abandoned (its disks
> > re-purposed/re-partitioned/reused).
> > 
> > If all of the above are true, then I recommend that you run 'zdb -l <disk>' for
> > all suspect disks and their partitions (or just all disks and partitions).  If
> > this command reports at least one valid ZFS label for a disk or a partition that
> > do not belong to any current pool, then the problem may affect you.
> > 
> > The best course is to remove the offending labels.
> > 
> > If you are affected, please follow up to this email.
> 
> GREATE!!!!
> in a diskless environment, /boot is read only, and the zpool.cache issue
> has been bothering me ever since, there was no way (and I tried) to re route it.

I believe zpool.cache is not required only for root pool anymore and
that you still need it if you want non-root pools to be automatically
configured after reboot. Am I right, Andriy?

Zpool.cache basically tells ZFS which pools should be automatically
imported and file systems mounted. You can have disks in your system
with ZFS pools that should not be auto-imported and zpool.cache is the
way to tell the difference.

-- 
Pawel Jakub Dawidek                       http://www.wheelsystems.com
FreeBSD committer                         http://www.FreeBSD.org
Am I Evil? Yes, I Am!                     http://tupytaj.pl