[HEADSUP] zfs root pool mounting

Daniel Braniss danny at cs.huji.ac.il
Fri Nov 30 07:06:40 UTC 2012

> 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.

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.


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