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Re: [Xen-devel] Re: [Xen-users] creating a domU with a particular UUID w

To: Tim Freeman <tfreeman@xxxxxxxxxxx>
Subject: Re: [Xen-devel] Re: [Xen-users] creating a domU with a particular UUID with xen-unstable
From: Anthony Liguori <aliguori@xxxxxxxxxx>
Date: Mon, 31 Oct 2005 19:22:11 -0600
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx, "Andrew D. Ball" <aball@xxxxxxxxxx>
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Tim Freeman wrote:

On Mon, 31 Oct 2005 18:12:52 -0500
"Andrew D. Ball" <aball@xxxxxxxxxx> wrote:

It looks like I can do this by starting a domain from an SXP directly instead of a Python-based configuration.

If I use a suitable algorithm for generating UUIDs, I should be able to guarantee at least an extremely low probability of UUID collisions across an entire farm of systems running Xen. I will read up some more on the ISO UUID algorithm commonly used by hardware manufacturers. I don't trust it quite yet, but it does seem that this is in line with its purpose.

I don't think Xen3 has changed, with UUIDs you'll run into this bug (for which I
have not yet submitted a patch for, I should do that).
It's a feature, not a bug :-)

You can use either domid's or names with all commands. For this to work, names cannot be integer. The simple check is to prevent names from beginning with numbers (which is a common enough requirement on symbols).

FWIW, I'd recommend just prepending uuid- to the name instead of trimming the front off.

Regards,

Anthony Liguori

http://lists.xensource.com/archives/html/xen-devel/2005-07/msg00090.html

I was hastily adding support for UUIDs to the Globus workspace control program
and ran up against this problem because UUIDs can start with digits. Because I
couldn't wait to rely on a Xen patch, what I ended up doing for that was
stripping digits from the beginning of the UUID before sending it to Xen which
is clearly only a temporary hack. Tim

I'm not really fond of the behavior of domain name collisions. I don't want to have to query some sort of farm-wide database to see if a domain name isn't being used to guarantee uniqueness, but I want to be able to guarantee that I'll never have a domain name collision when doing a live migration of a domU to another system. They are nice to have around for being easily readable by humans though.

Thanks for your help.

Andrew

Anthony Liguori wrote:
Andrew D. Ball wrote:

Is it possible with xen-unstable (hopefully soon to be Xen 3.0) to create a domU with a particular UUID? I don't want the UUID for a domain to change when I destroy it and create it again from the same configuration.
You could always make the domain's name it's UUID.

Regards,

Anthony Liguori

This doesn't necessarily have to have anything to do with xenstore's being persistent, it could just involve a configuration option similar to the one for virtual NICs where MAC addresses can be assigned explicitly if desired but will be pseudo-randomly generated otherwise.

Thanks for your help.

Andrew



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