[OpenIndiana-discuss] Moving /var and/or /usr to own zfs filesystem

[James Carlson]

On 09/10/13 12:31, Ben Taylor wrote:
> I really can't see the wisdom of splitting out /usr from / on a ZFS file
> system.  I had an open bug with Sun in 2009 regarding the separate /var
> partition, and we went months arguing with support regarding whether or not
> that was a supported configuration.

It'd be somewhat interesting to know the details on how it could be
argued, because a separate /usr and /var are explicitly described in
filesystem(5).  As with all things on Solaris, the official reference on
what ought to work (and what is not documented to work) is the man page.

However, a separate /usr makes no real sense to me in this day and age,
given that the only substantial reason that support ever existed was for
the extremely wacky "clients with tiny root disks and NFS-mounted /usr"
configuration.  Nothing other than unusually good fortune could protect
someone trying to do that in 2013.

A separate /var makes sense to me, but you do need to be a bit careful
with it, and I would not be shocked to find that there things there that
don't work terribly well.  In particular, I'd expect that you have to
use legacy (/etc/vfstab) mounting in order to make it work.

For what it's worth, I don't do that on my own systems.  I just create
zfs mounts over the key (growable) mounts below /var ... particularly
/var/cores (where I set coreadm), /var/crash, /var/mail, and /var/log.
Plus, having separate sub-mounts gives me much finer-grained accounting
and control.  That's sort of the whole point of ZFS.

> My point being is that, a separate /usr ZFS file system has had no support
> or testing for this type of configuration.

Testing is a separate and much more important point, I think: if you do
things the way nobody else does them, intentionally or otherwise, then
you're a test pilot.  Much luck, and make sure you've repacked your
parachute recently.

-- 
James Carlson         42.703N 71.076W         <carlsonj at workingcode.com>