mounting failed with error 2

[Jay Borkenhagen]

Andriy Gapon writes:
 > >  > Failing that, you can set vfs.zfs.debug=1 at loader prompt before
 > >  > booting.  That could shed some light on what is going wrong.  The
 > >  > most likely possibility is that /boot/zfs/zpool.cache in the
 > >  > boot/root filesystem of the boot/root pool does not have an entry
 > >  > for the root pool.
 > > 
 > > I just tried 'set vfs.zfs.debug=1' then 'boot' at the loader prompt,
 > > and it seems I wound up at the exact same place with no further debug
 > 
 > It's not further, it's before that.

I could not see any difference in the output to the console by having
done 'set vfs.zfs.debug=1' -- not before, not after.

 > > diagnostics.  I believe the important part of that error output is
 > > this: 
 > > 
 > > ===============
 > > Trying to mount root from zfs:zroot/ROOT []...
 > > Mounting from zfs:zroot/ROOT failed with error 2.
 > > 
 > > Loader variables:
 > >   vfs.root.mountfrom=zfs:zroot/ROOT
 > > ===============
 > >