[CentOS-virt] Preferred method of provisioning VM images

Thu Jun 12 08:12:21 UTC 2014
Dario Faggioli <raistlin at linux.it>

On gio, 2014-06-12 at 07:17 +0200, lee wrote:
> Lars Kurth <lars.kurth at xen.org> writes:

> Let me wear the hat of the user.  The major hurdles were network setup,
> installing something in a vm, and the chaotic state the documentation is
> in.
Wow... "chaotic state" :-O

Don't get me wrong. I know everything can always be improved, and
documentation is --for free software in general, which well includes
Xen-- often in a position of needing _a_lot_ of improvement.

All that being said, it would be helpful if you could be a bit more
specific and help us actually improve it. I think you've said, in
another thread, that you requested editor access to the wiki, but don't
know what status such request is in (provided I'm not mistaking you with
someone else, in which case, sorry! :-P). Can you double check, so that
we can see how to move forward and allow you to act instead of only
complaining. :-D

> As a user, I'm used to get an ISO of an installer or of a life system,
> put that into a DVD drive or write it to an USB stick and to boot from
> that to do the installation.  Why can't I do that with xen?
Wait, what? Who said you can't do it? Of course you can! In fact, if you
tried and it failed, please, report the bug within the appropriate
channel, because a bug is what that is, nothing less! :-O

However, I think we're talking about something different here...

> > == #1 virt-install ==
> > == #2 xen-tools ==
> > == #3 virt-builder (http://libguestfs.org/virt-builder.1.html) ==
> > == #4 Cloud Image from Cloud Image SIG ==
> I wouldn't want #4.  I want to be able to just use the installer of
> whatever distribution I'm installing in a VM and a simple way of saying
> "run this in a VM and let me install".  Or perhaps I merely want to run
> a life system in a VM to try it out, with network access.  What easy way
> is there to do that?
I'm not sure I got what you mean with 'I merely want to run
 a life system in a VM to try it out'. If you mean trying out Xen in a
VM, then of course you need a nested-virt capable platform. If you have
one, here's the instructions of how to create a Xen liveCD. I'm afraid
both the instructions and the liveCD are Fedora based, but it should not
be a big deal to bias them toward CentOS:


I also don't know much of #3, but at least #1 and #2, are both meant at
doing exactly what you're saying: "install this in a VM", they only
happen not to require install DVDs. I understand that DVDs are your
preferred method, but that doesn't make it the one _everyone_ prefer!

AFAIUI, when talking about this kind of provisioning, what we're
interested is something a lot more automated and, as a consequence, a
lot less interactive than an installer.

> For example: http://wiki.xen.org/wiki/Credit_Scheduler:
Ok, now we're talking! That's what I meant when asking to 'be
specific'! :-)

> "It is now the default scheduler in the xen-unstable trunk."
> So is it the default in the version I'm using or what?
Good point, I'll fix this.

> "The SEDF and BVT schedulers are still optionally available but the plan
> of record is for them to be phased out and eventually removed."
> What are those and have they been removed in the version I'm using?

> "Schedule Rate Limiting (added in Xen 4.2)"
> That doesn't belong there.  It needs to go into the documentation for
> that particular version of xen.
> "Timeslice (added in Xen 4.2)
> [...]
> # xl sched-credit -t [n]"
> dito
I don't agree. I think they do belnog. Of course, that does not mean we
can't link to them from a 'Xen 4.2' page.

> I always admire the documentation exim has ...  As to your original
> question:
> > I was wondering whether we need to look at a standard way in which we
> > recommend how to provision images for VMs.
> I'd suggest to start with splitting the documentation into different
> versions, one version of documentation for each version of xen.  Some
> way to get a VM running may then be discovered and improved upon.
Personally, I don't think that would be the optimal split, or something
we need to do right now (which does not mean we should not improve docs
in other ways). However, I think you're way off the 'original question'
which, again, was about provisioning.


<<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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