failed to create gmirror with the handbook instructions

[Warren Block]

On Tue, 8 Oct 2013, Andy Zammy wrote:

> This is actually trickier than it first looked. First I got into single user mode by supplying 'shutdown now', but the tunefs commands all failed with the following:
> #tunefs -j disable /dev/ada0s1a
> Clearing journal flags from inode 4
> tunefs: Failed to write journal inode: Operation not permitted
> tunefs: soft updates journalling cleared but soft updates still set.
> tunefs: remove .sujournal to reclaim space
> tunefs: /dev/ada0s1a: failed to write superblock
> 
> I tried the dump command on the off-chance, and it failed with the original errors. Is there anything you can recommend?
> 
> I then noticed you specified to boot into single user more, so I restarted the machine, with only ada0 attached. Because the handbook wants me to use the mirror/gm0sX devices, I swapped
> my fstab file back to the original. The boot loader now only seems to recognise the mirror/gm0 nodes, the original ada0sX are gone (though ada0 still shows up).

I don't know what would do that.  The device nodes on the original drive
should be untouched until it is added back to the mirror.  What does
   gpart show ada0s1
show?  Did you make a backup of the original drive first?  Is there an 
entry for vfs.root.mountfrom in /boot/loader.conf?

> I'm not sure if it's acceptable to do the dump by booting the 1st hard 
> drive using the mirror/gm0, and then dump to the 2nd hard drive by 
> mounting what will be ada1sX. Is this okay to do?

Sorry, I don't quite understand the question.  The mirror will not be 
usable until a good copy of the original drive is made to it.