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

[Tim Freeman <tfreeman@xxxxxxxxxxx>]

On Mon, 31 Oct 2005 19:22:11 -0600
Anthony Liguori <aliguori@xxxxxxxxxx> wrote:

> 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).

Sure ... but as we talked about in the thread I linked, it could check for all
numbers instead.  It's irrelevant to us now, but it did come as a surprise I
couldn't use something so useful as a straght uuid.

By the way, at the very least, the inclusion of "/" should be removed, it leads
to an error state.

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

That does sound like a better idea, thanks. 

Tim 


> 
> 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
> >>>>
> >>>>
> >>>>
> >>>>_______________________________________________
> >>>>Xen-users mailing list
> >>>>Xen-users@xxxxxxxxxxxxxxxxxxx
> >>>>http://lists.xensource.com/xen-users
> >>>>
> >>>>        
> >>>>
> >>>      
> >>>
> >>
> >>_______________________________________________
> >>Xen-devel mailing list
> >>Xen-devel@xxxxxxxxxxxxxxxxxxx
> >>http://lists.xensource.com/xen-devel
> >>
> >>    
> >>
> >
> >  
> >
> 

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