Easier interface for kickstarting Xen VMs

Easier interface for kickstarting Xen VMs

[Edward Z. Yang]

Hello all,

When you're embedding an HTTPD server into your Xen configuration
file, you know there's something wrong. :-)

I was curious to know if there would be any interest in offering
a more polished, easier to use interface for kickstarting Xen
VMs.  No mucking around with ks= and trusted web servers: just
say where your kickstart file is and Xen will take care of the rest.
Maybe even let you do a little preprocessing the same way you
can use Python scripting to support multiple machines out of one
configuration file.

We have a few ways of how we might do this: the "temporarily spawn
an HTTP server" is one of them but other possibilities include
mounting multiple initrds (doesn't actually work with Anaconda, we're
looking into it) and exporting a small, temporary filesystem to the VM.
If there's interest, we'll clean up our code and submit it.

Cheers,
Edward

Re: Easier interface for kickstarting Xen VMs

[Stefano Stabellini]

On Mon, 20 Sep 2010, Edward Z. Yang wrote:
> Hello all,
> 
> When you're embedding an HTTPD server into your Xen configuration
> file, you know there's something wrong. :-)
> 
> I was curious to know if there would be any interest in offering
> a more polished, easier to use interface for kickstarting Xen
> VMs.  No mucking around with ks= and trusted web servers: just
> say where your kickstart file is and Xen will take care of the rest.
> Maybe even let you do a little preprocessing the same way you
> can use Python scripting to support multiple machines out of one
> configuration file.
> 
> We have a few ways of how we might do this: the "temporarily spawn
> an HTTP server" is one of them but other possibilities include
> mounting multiple initrds (doesn't actually work with Anaconda, we're
> looking into it) and exporting a small, temporary filesystem to the VM.
> If there's interest, we'll clean up our code and submit it.
> 

You should be aware that we are trying to move away from xend to xl,
that generally supports the same VM config file format with just one
exception: embedded python.

Considering that kickstarting Xen VMs is a common problem and probably
the main headache for sysadmins when moving from xend to xl, I would
welcome a clean and small solution to this problem that doesn't involve
embedded python.
If we go with the temporary fs strategy, I guess there isn't any actual
code to be committed to xen-unstable, but rather a wiki page to
describe the solution and a link to the initrd? 

Re: Easier interface for kickstarting Xen VMs

[Edward Z. Yang]

Excerpts from Stefano Stabellini's message of Tue Sep 21 12:46:53 -0400 2010:
> You should be aware that we are trying to move away from xend to xl,
> that generally supports the same VM config file format with just one
> exception: embedded python.

Stefano, that's really interested!  None of our current team was aware of
this fact; probably because we're still on Ubuntu 8.04 due to Xen's
special packaging situation on this platforms.

> Considering that kickstarting Xen VMs is a common problem and probably
> the main headache for sysadmins when moving from xend to xl, I would
> welcome a clean and small solution to this problem that doesn't involve
> embedded python.

That's great to hear.  The point of the solution is to do away with the
embedded Python.

> If we go with the temporary fs strategy, I guess there isn't any actual
> code to be committed to xen-unstable, but rather a wiki page to
> describe the solution and a link to the initrd? 

Considering that any given Kickstart file needs to be converted into an
initrd, there would be code involved.  I am also unconvinced that Anaconda
actually /works/ with layered initrd, see my post here:

    https://www.redhat.com/archives/kickstart-list/2010-September/msg00015.html

Cheers,
Edawrd

Re: Easier interface for kickstarting Xen VMs

[Stefano Stabellini]

On Tue, 21 Sep 2010, Edward Z. Yang wrote:
> Excerpts from Stefano Stabellini's message of Tue Sep 21 12:46:53 -0400 2010:
> > You should be aware that we are trying to move away from xend to xl,
> > that generally supports the same VM config file format with just one
> > exception: embedded python.
> 
> Stefano, that's really interested!  None of our current team was aware of
> this fact; probably because we're still on Ubuntu 8.04 due to Xen's
> special packaging situation on this platforms.
> 

xl/libxl is still under heavy development, the first version that should
be stable enough for production use is going to be released with xen
4.1.



> > Considering that kickstarting Xen VMs is a common problem and probably
> > the main headache for sysadmins when moving from xend to xl, I would
> > welcome a clean and small solution to this problem that doesn't involve
> > embedded python.
> 
> That's great to hear.  The point of the solution is to do away with the
> embedded Python.

Yes, exactly.


> 
> > If we go with the temporary fs strategy, I guess there isn't any actual
> > code to be committed to xen-unstable, but rather a wiki page to
> > describe the solution and a link to the initrd? 
> 
> Considering that any given Kickstart file needs to be converted into an
> initrd, there would be code involved.  I am also unconvinced that Anaconda
> actually /works/ with layered initrd, see my post here:
> 
>     https://www.redhat.com/archives/kickstart-list/2010-September/msg00015.html
> 
 
Ok then we can convert kickstart files into temporary iso images or read
only disks?

Instead of implementing this feature directly in the toolstack maybe it
is better to have another tool take a ks file and generate the
VM config file and the temporary disk. This way the whole process would
be a more transparent and flexible.