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Re: [Xen-devel] will this clever plan work?

To: mark.williamson@xxxxxxxxxxxx
Subject: Re: [Xen-devel] will this clever plan work?
From: "Eric S. Johansson" <esj@xxxxxxxxxx>
Date: Thu, 11 Nov 2004 11:34:02 -0500
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Mark A. Williamson wrote:
I thought of two applications for Xen that could be amusing.  First is
as a base for a firewall.  The idea would be that in order to upgrade to
the next release of the firewall, you would create a new virtual machine
image and disable (but not necessarily expire) the previous version.

It should be possible to build something like that on top of Xen. It'd be quite cute too ;-)

and if I could make it run out of flash memory, it would be the cat's ass[1]

 > One nice way to set this up would be:
* admin software in dom0 (accessed via console or dedicated NIC)
* a separate domain for the firewall software, controlling the NICs directly
* when you upgrade, kill the old domain and build a new one (this can be scripted and should be a very quick process with minimal downtime)

can the two domains communicate over a virtual NIC? the reason I ask is that since most of the control is by a Web interface, we would need to tickle the control system in dom0 or at least proxy to it.

My fantasy is that I will be able to build a single disk image for all
of the basic OS and application to be shared between multiple virtual
machines.  Update that single core image using Gentoo magic and be able
to have separate partitions holding my application data.

Yes, you should be able to do that. If you're using VBDs (not NFS), the standard caveats for shared data apply:
* domains can't write to the shared data
* you can't update the shared data while the domains are running (otherwise you'll confuse them)

I really need to learn how the whole storage metaphor is organized.. I don't know enough to ask the right questions yet. I probably should just set up a system with a real standard disk image and partitioning and start breaking it.

on a humorous aside, VBD used to refer to people who are so insecure in their manhood that they used proxies like expensive cars, trophy wives, etc. to show that they had a VBD.


[1] well, since our feline buddies are always waving their butts in our faces like it was the best thing on the face the planet, if it's good, it must be the cat's ass ;-)

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