[PATCH] mkfs.xfs: add [-U uuid] option

[Dave Chinner]

On Tue, Sep 22, 2015 at 01:56:53AM +0300, Mika Eloranta wrote:
> On 22 Sep 2015, at 01:18, Dave Chinner <david at fromorbit.com>
> wrote:
> > 
> > On Mon, Sep 21, 2015 at 08:04:20PM +0300, Mika Eloranta wrote:
> >> The UUID can now be optionally specified during filesystem
> >> creation.
> > 
> > Which UUID are you wanting to set - the metadata uuid or the
> > user visible UUID label? Or both? Can you explain the use case
> > for this?  i.e. I'm trying to work out why Why doesn't mkfs.xfs
> > + xfs_admin -U <uuid> doesn't work for you?
> 
> I want to set the user visible UUID (same as xfs_admin -U/-u).
> Whether this impacts the "metadata uuid” or not, I do not
> know, I’m not an expert on the XFS internals, just a user.

Which tells me what I need to know - You are trying to use the UUID
as a user controlled filesystem label. Funnily enough, we have a
thing for this already - a user controlled filesystem label:

# mkfs.xfs -L "label" ....

It's 12 characters long, so more than enough for any sort of unique
identification scheme you want to use for your filesystems.
xfs_admin enables you to change it after the fact, all major
filesystems support it and all the infrastructure know about it
(lsblk, /etc/fstab. /dev/disk/by-label, etc) so using it is no
different to using UUIDs. Except that, unlike UUIDs, you can make
fileystem labels human readable. :)

Perhaps you should try using filesystem labels seeing as everything
you need is already there?

Cheers,

Dave.
-- 
Dave Chinner
david at fromorbit.com