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Re: [Xen-users] Bootable LiveDVD w/ Xen that boots Windows Image?

On Fri, Aug 14, 2009 at 1:37 AM, Joshua
Kinard<joshua.kinard@xxxxxxxxxxxxx> wrote:
> Hmm, I didn't think of it that way.
> The way I read up on UnionFS and aufs' functionality, was they could 
> essentially merge two files virtually,

Merge two directories together, to be exact. Not merge files.

> i.e., the kernel module would be able to look at the operation coming in and 
> route it to the proper descriptor (i.e., read() --> /livecd/windows/winxp.img 
> OR write() --> /tmp/winxp.img, with /tmp being in tmpfs).  I guess it's not 
> as granular as that it seems.  Would be a neat trick, but I imagine it'd be 
> complex as anything for a kernel module to have to keep track of which files 
> have variants loaded in the writeable union area.

What you describe is essentially block-level copy-on-write, which is
what qcow or zfs does. Aufs/unionfs does this per file.

> As for the application, it's a complex network security scanner, made by eEye 
> Digital Security, called "Retina".  We just don't want to setup and baby sit 
> Windows installations on our Unix networks strictly for this one app, so I 
> figured if I can get it to run off of a CD, we can just park some diskless 
> hardware in a closet and pull it out whenever we need to do network testing 
> and such.

If it were me I'd simply setup a Windows domU on any server with
enough disk and RAM, make a "template" of the "good" installation
(preferably zfs or LVM snapshot), start it only when it's needed, shut
it down afterwards, and (if necessary) rollback to the "good"
template. That is assuming that all host/network tested reachable from
my datacenter (either with vlans or routing). No need to add the
complexity of a live DVD/USB.

If portability is a requirement, and you're absolutely sure you'll
always have VT-capable host handy, then using live USB is much
perefered than DVD due to performance and complexity reasons. But hey,
that's just me :D

Let us know if you find a solution that works.


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