On Thu, Dec 07, 2006 at 06:09:11PM +0000, Daniel P. Berrange wrote:
> I've been testing out the inactive domain support in more depth, and looking
> for any odd interactions with xm and/or libvirt. In doing so I seem to have
> found some problems with changing the configuration of existing domains.
>
> Since the config files are no longer in /etc/xen, users will no longer simply
> be able to edit them to tweak parameters before booting. Changing the files
> under /var/lib/xend/domains is not practical because XenD won't see the
> changed files (unless it uses Inotify - which it doesn't).
>
> I don't think we need to worry about changing every single parameter at this
> time, but the basic set of memory, max memory, vcpu count should definitely
> be made to work with 'xm' / XMLRPC / SEXPR apis. If it was practical I'd
> also like to see the network & block device add/remove APIs work for inactive
> domains too.
>
>
> Currently, this sort of works, but results in very wierd bugs. eg changing
> the VCPUs for a guest:
>
> So, I have a guest with 2 vcpus:
>
> # xm list
> Name ID Mem VCPUs State
> Time(s)
> Domain-0 0 2981 2 r----- 2381.2
> demo 410 2 0.0
>
>
> And want to change it to have 8:
>
> # xm set-vcpus demo 8
> Command set-vcpus is deprecated. Please use xm vcpu-set instead.
> Error:
> Usage: xm <subcommand> [args]
> [sniped rest of error]
>
> So it apparently failed, but it actualy succeeded....
>
> # xm list
> Name ID Mem VCPUs State
> Time(s)
> Domain-0 0 2981 2 r----- 2381.7
> demo 410 8 0.0
>
> What's even wierder, is if I now go and try to start the guest I end up
> with 2 copies of it !!
>
> # xm start demo
> # xm list
> Name ID Mem VCPUs State
> Time(s)
> Domain-0 0 2981 2 r----- 2382.9
> demo 45 410 8 -b---- 0.8
> demo 45 410 8 -b---- 0.8
After a little more debugging, this duplicate domains problem seems to be
unrelated to the changing of config params.
I defined an inactive guest with a UUID of
'66857c70-9898-fdfc-ed53-8eee3ba294bf'
which got stored on disk as
/var/lib/xend/domains/66857c70-9898-fdfc-ed53-8eee3ba294bf/config.sxp
When starting the guest, however, it got a UUID of
66857c709898fdfced538eee3ba294bf
so it thought there was a dup. So, XenD needs to normalize UUIDs to remove any
embedded '-' when saving the inactive domain config to avoid this duplicate
domains issue.
Regards,
Dan.
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