mountroot prompt with error2, when trying to boot from a single drive in a 2-way mirror

Matthew Seaman matthew at
Tue Apr 14 13:17:56 UTC 2015

On 2015/04/14 13:35, yudi v wrote:
> I was testing recovery scenario by removing one of the drives in a 2-way
> mirror, but the system fails to boot and comes up with the mountroot prompt
> with error 2. When I reconnect the second drive, it boots fine again.
> Any suggestions on what the problem might be?
> it's a simple root-on-ZFS setup (9.1 upgraded to 10.1 recently) with two
> disks in mirror config.
> each disk has 3 partitions, first one has the boot code, second has the
> swap, third has the OS.
> and the zfs pool is setup on the 3rd partition of the two disks.

Check the BIOS settings -- there will be a list giving the order of
preference for devices to boot from.  Frequently you'll find there is
one slot for 'Harddrive' and you get to select just one of the drives
attached to the system to boot from.  In this case, simply telling it to
use the other disk should allow you to boot.  Otherwise, if your bios
allows you to specify several hard drives, then reordering the drives in
the preference list might make it work.  This last really shouldn't be
necessary, but not all BIOSes are created equal.



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