Re: [Xen-users] Basic questions - numbered

[Tim Deegan <Tim.Deegan@xxxxxxxxxxxx>]

Hi Ted,

I have a few brief answers to some of your points below, to follow up
from Mark:

>  Then I tried it on two Linux machines (again that does not matter 
> as it's a Live CD).  But the Live CD would not boot.  Ouch!!! After 
> several days of testing I discovered (even though the bios was properly 
> set so the CD should boot) that even an OS independent Smart Boot could 
> not force the CD to boot nor even detect it. Even a SuSE CD self booting 
> installation would not boot.

Yep, sounds like your machines don't boot from CD-ROM.  Things that are
worth trying in this situation:

- SBM (Smart Boot Manager) floppy:  http://btmgr.sourceforge.net/download.html
- GrUB floppy: http://www.gnu.org/software/grub/grub-legacy-faq.en.html#q4

A floppy boot image for the demo CD is unlikely to happen because the 
initrd the CD uses is significantly larger than will fit on a floppy. :)

> If this seems feasible (moving a pre built Linux installation into a 
> logical partition for this purpose) could I have an example of a GRUB 
> configuration file as a kind of template for a dedicated multiple 
> logical partitions boot???

I'm not sure what your question is, but the GrUB runes for booting Xen
are discussed in the Xen user's manual:

http://www.cl.cam.ac.uk/Research/SRG/netos/xen/readmes/user/user.html#SECTION02240000000000000000
 
> Is the "grub.conf" file associated with the LIVE CD a good example of 
> what I am looking for and how do I discover it's contents??? 

The grub configuration on the CD is in /boot/grub/menu.lst on the CD; you
should be able to read that file from a running system.

> Can I do the following?
> 
> "dd" the Live CD into one of these partitions mentioned above and boot 
> to this "copy" on hard drive instead of CD???

In theory, yes, but why would you?  The filesystem on the demo CD has a
bunch of tweaks to make it run from CD (i.e. without writeable disks,
and running several OSes from the same image).  Starting from that would
give you something that's not quite a proper Debian install, and
something that's not quite the proper Xen tools on top of it, which
would just cause problems later on.

Basically, the demo CD is intended to be just that: a demo.  It's *not*
meant as a production platform.

You would really be *much* better off installing a linux distro from
scratch and then installing Xen into it.  Recent versions of Debian have
excellent support for installing in difficult cases, and it sounds like
your Suse install floppies work too.


> That's how I read it. But this is where I am 
> most confused because the Xen-based system has it's own bridge 
> (assumedly to virtualize network connectivity) and I would think that 
> each DomU or virtualization including Dom0 would also need a bridge to 
> talk to my LAN machines or I've got this wrong and the bridges just join 
> networks. (Sorry, but I am missing a bit of network insight here). 

The demo CD doesn't use the network card of the machine.  Domain 0 talks
to all the other domains via the 'xen-br0' bridge, which has the IP
address 10.171.45.1.   You should be able to bring up real LAN
interfaces separately with the usual linux tools.   You can then setup
NAT between the inside (other domains via xen-br0) and the outside
(LAN).  Read the man page for iptables for more details on how to do athat.

Tim.

-- 
Tim Deegan                           (My opinions, not the University's)
Systems Research Group
University of Cambridge Computer Laboratory

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