Re: [Xen-users] First time xen install - Xen DomU runs, but can't find "/dev/root"

[Dario Faggioli <dario.faggioli@xxxxxxxxxx>]

On mar, 2013-10-22 at 23:03 +1100, G Crowe wrote:
> On 21/10/2013 5:28 PM, Dario Faggioli wrote:
> > When doing what? I'm usually able to 'define', 'creade', 'shutdown',
> > 'undefine' and 'create' again.
> >
> > What is your issue with that?
> >
> This is probably just my ignorance , please see my output below...
> Note that "xl define" and "xl undefine" both return "command not 
> implemented".
> 
Uh, sorry, I probably explained myself bad. :-( Those "define" and
"undefine" commands are from libvirt, so you have access to them via
`virsh', rather than `xl'.

> ********************
> Scenario 1, stopping and then restarting a DomU
> - I can shutdown a DomU with "xm", "xl", from within the DomU with 
> "shutdown -r now", or by rebooting Dom0.
>
Ok.

> - xl seems to lose any memory of the DomU at this point (well, I can't 
> figure out how to bring it back) and "xl list" doesn't show it while it 
> is stopped.
> - xm can remember it and restart it. "xm list" will still list the 
> stopped DomU.
>
Right, and that's by design. One of the differences between xl and xm is
that the latter remembers (you usually say 'manages') domains even when
they're not running, while xl forgets about them. That happens because,
together with xm, you have the xend daemon doing right that, while with
xl there is no such thing (you always have daemons running, like
xenstore, etc, but not for that purpose).

> - "xl create" seems to want a config file, which I don't have. "xm 
> start" just starts the DomU that has already been configured, without 
> needing an additional config file.
>
Right, because you created the DomU via virt-install, right? Well,
ideally, there would be a "xen-xl" sub-command available for `virsh
domxml-to-native", which would give you exactly the config file you're
looking for. This is quite a big issue (at least according to me) with
the libxl libvirt driver... We'll try to look into that ASAP!

> ********************
> Scenario 2, deleting and then recreating a DomU
> - I can delete a DomU with "xm destroy xen2" then "xm delete xen2"
> - When trying "virt-install" - If xend is not running (it defaults to 
> the xl toolchain?) 
>
Yes, that's how libvirt works (defaults to the libxl driver if xend is
not running), and virt-install does use libvirt.

> then I cannot recreate xen2 with virt-install.
>
No, you can't, but you should be able to start it with `virsh'.

Try something like the following (after shutting down xen2):

# virsh list --all

it should list xen2, in a non-running (or stopped, or something like
that) status.

After that:

# virsh start xen2

should bring it up.

Finally, sorry for replying a bit late, but I'm traveling these days.

Regards,
Dario

-- 
<<This happens because I choose it to happen!>> (Raistlin Majere)
-----------------------------------------------------------------
Dario Faggioli, Ph.D, http://about.me/dario.faggioli
Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)

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