[Xen-users] Re: How was CoW implemented on the Demo LiveCD (3.0) ??

[Rickard Borgmäster <doktorn@xxxxxx>]

Tim Deegan wrote:
> On Tue, Jan 24, 2006 at 11:33:43AM +0100, Rickard Borgm?ster wrote:
>
> > I need to know what's needed to implement cow filesystem for domU the 
> > same way it was done on the LiveCD demo for xen 3.0. Our current project 
> > it is replace UML with XEN on a bootable router simulation LiveCD. We 
> > need to make each domU machine share the same rootfs.img. And I know it 
> > is possible, as it was done on the demo LiveCD. But how?
> I think you'll need to copy over some of the scripts from the demo CD:
>
> /etc/xen/scripts/block-cow
> /usr/sbin/create_cow    
> /usr/sbin/destroy_cow
Hey Tim, thanks for your answer. I realized that this could be the case, 
that there were scripts on the CD not included in the distribution.
I've been struggling with this all day now. Sigh. And ppl they say that 
computer work cannot be exhausting :-/
Well, anyways. I've put those files into place and been trying to get it 
to work in many different ways. zNone worked :-(
The only meaningful error message I can find is:
Error: Device 769 (vbd) could not be connected. Backend device not found.

Since I'm new to CoW aswell, i do not know what to look for. I realize 
that I should see some devices in /dev/mapper (which I don't). But I do 
not know how to troubleshoot. Anyways, I just realized that I could 
"test run" the scripts manually if I just can figure out the parameters. 
And what do you know... I got results. create_cow without the -q 
parameter reported that dmsetup was missing. Some apt-get later... it 
just worked. My co-workers had their ears blown out by my heureka...
Well, now I'm off home. Hope to make some more progress on the livecd 
tomorrow :-)
Best regards
Rickard Borgmäster


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