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Re: UUID in fstab for device mapper devices?

Guido Günther <agx@sigxcpu.org> writes:

> On Sun, Aug 09, 2009 at 09:31:48PM +0200, Ferenc Wagner wrote:
>> Guido Günther <agx@sigxcpu.org> writes:
>>> Dropping user_friendly_names won't give you name persistence with
>>> and without mp all by itself. You'll either have to use disk/by-id
>>> or disk/by-uuid to achive that.
>> Why not?  The WWIDs, which are used to name the devices by default,
>> are persistent and also consistent between machines, aren't they?
> Yes, these are persistent across machines but they aren't persistent
> as to switching multipath on and off (see below).

Hi Guido,

Thanks, I got your point now.

> We could have the same fstab with and without multipath. This would
> be convenient for our users since they'd have easier means of error
> recovery (and an easy way to turn multipath on and off):

And to run without multipath without noticing until the first path

> Without multipath:
> /dev/disk/by-uuid/<UUID> -> /dev/sdaY 
> With multipath:
> /dev/disk/by-uuid/<UUID> -> /dev/mapper/<WWID>-partY

Multipath is critical enough in my systems that I prefer explicit
control and early failure dealing with it.  Others may have different
preferences, of course.

Also, how does this carry over to multipathed root?  I'd guess
initramfs needs the real device name after root= anyway, doesn't it?

>> To get really friendly names, I define aliases in multipath.conf,
>> but that's mostly sugar, I could do without them.  Losing name
>> consistency amongst different machines would be a major
>> inconvenience, though.
> I wouldn't object getting rid of user_friendly_names in
> multipath.conf, but preferably by switching to /dev/disk/by-{uu,}id
> then.

I'd welcome that.  It may not be the exact thing I'd want, but good
enough to start from.  I may as well get to love it in the end. :)

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