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

To: "'Joshua Kinard'" <joshua.kinard@xxxxxxxxxxxxx>, <xen-users@xxxxxxxxxxxxxxxxxxx>
Subject: RE: [Xen-users] Bootable LiveDVD w/ Xen that boots Windows Image?
From: "Dustin Henning" <Dustin.Henning@xxxxxxxxxxx>
Date: Mon, 24 Aug 2009 13:04:48 -0400
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        Regarding your comment on GPLPV, it does not expose any real
hardware to the HVM domU; it exposes and provides drivers for the PV devices
that are always used by PV domains (instead of the fully virtualized devices
typically used by HVM domains).  I don't believe the PV devices change when
the hardware on a machine changes (just the fully virtualized devices don't
change), so the GPLPV drivers should provide performance enhancement without
adding any new potential (non-driver related) issues once they are working
on a LiveDVD (because nothing should change in terms of what your guest is
seeing once you have everything on RO storage).

-----Original Message-----
From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx
[mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Joshua Kinard
Sent: Thursday, August 20, 2009 09:48
To: xen-users@xxxxxxxxxxxxxxxxxxx
Subject: RE: [Xen-users] Bootable LiveDVD w/ Xen that boots Windows Image?

Yeah, I've looked at the GPLPV stuff, and it looks like it'd expose Windows
to the real hardware.  While that has big performance benefits, since this
would be on a CD that could visit multiple machine configurations, leaving
the driver detection to the underlying Linux distro, and virtualizing stuff
for the Windows guest will be the more preferred route (because don't we all
love Windows' brain-dead driver detection, especially in XP?).

I did try taking a look at BartPE initially, but making a plugin for the PE
environment proved futile, as there are just way too many registry entries
created by the scanning program upon install.  WinPE was another option (and
it's free now as well), but it won't run .NET code at all, so that idea was
ruled out.  Wine got nowhere, and VMWare/VirtualBox have too many license
restrictions.  Although the end result will be an internal tool, some of the
knowledge I'm piecing together for this will wind up in the community
(mostly the device-mapper concepts I imagine), but we still want to be as
legit as possible internally.  It's just good practice :)

SquashFS takes care of the RAMDisk problem.  A 7.1GB WinXP disk image,
internally consumes 2.7GB after all the XP patches are applied (per MBSA
2.1), and my network scanner program installed with its latest audit
updates.  But that gets compressed down to 1.3GB with SquashFS 3.1.  I might
try to kludge 4.x onto my Debian setup for their performance/compression
enhancements, but we'll see.  On a 4.7GB DVD, that still leaves me quite a
bit of room for the Linux root, and being Debian based, that will be really
small, especially with its own SquashFS glue and the appropriate boot
scripts in the initramfs.

The plus is I've learned a ton about Xen and virtualization, previously
having only been a VMWare guy.  So I've got other ideas that'll bubble up in
my head on how to leverage all of this down the road, too!



From: John Lewis [jlewis@xxxxxxxxxxxxxx]
Sent: Wednesday, August 19, 2009 6:46 PM
To: Joshua Kinard
Subject: Re: [Xen-users] Bootable LiveDVD w/ Xen that boots Windows Image?

Thanks for the info! Sounds like you have an interesting solution in
the works to your challenge. Its a shame that microsoft doesn't have a
live dvd distro for this type of need. I would suggest putting the
entire sparse image of windows into sort sort of ramdisk. I am more of
a domu/windows/pv driver guy so I am not sure how you would go about
doing this with the live distro you are choosing.

Good luck, sounds like an interesting project. I am looking forward to
hearing what the final resolution is (if it isn't in the list already).


On Aug 19, 2009, at 11:37 AM, Joshua Kinard wrote:

> Yup, thumb drives, SD cards, MMC, etc, aren't an option where I'm
> at.  I maintain several offline networks for testing software, and
> they all run various UNIXes, but no Windows setup.  Higher level
> management wants us to run vuneralbility scans on these networks
> using a Windows-based product (which I referenced earlier), but
> telling them "We don't use Windows" won't work.  So I was looking
> for a way to scan the networks without maintaining a Windows install
> on each one specifically for this one program.
> Hence, booting Windows off of a LiveCD pre-loaded with everything I
> need (and fully licensed, because we have a site license).  Unique
> problem, unique solution....just needs some more glue to put it all
> together.  I can update the one Windows install as-needed, load
> newer audit information, burn it to CD, and run my scans.
> Hope that clears things up!
> --J
> ________________________________________
> From: John Lewis [jlewis@xxxxxxxxxxxxxx]
> Sent: Wednesday, August 19, 2009 1:24 PM
> To: Joshua Kinard
> Cc: xen-users@xxxxxxxxxxxxxxxxxxx
> Subject: Re: [Xen-users] Bootable LiveDVD w/ Xen that boots Windows
> Image?
> Two questions, probably the same answer. I am just trying to
> understand why you are trying to do this, and what practical use this
> has. Maybe I will have a use for this in the future.
> What is the goal in doing this?
> Are usb thumb drives not an option?
> Lewis
> On Aug 19, 2009, at 7:56 AM, Joshua Kinard wrote:
>> Hmm, I don't think qcow format is going to work with that method.
>> At least when I tried it, the bochs bios didn't like what it was
>> looking at.  But it's hard to tell if that was bochs, or ntldr
>> giving me a fit.
>> I do know that RAW images work fine, though, and I just tested it
>> with squashfs by running mksquashfs on the base image, and mounting
>> that via loop2 to my base/ subfolder.  Then re-created the scratch
>> area, ran dmsetup, and booted.  Loaded up great, did some changes,
>> shutdown, unloaded the mapper device, unloaded the scratch loop,
>> unmounted my tmpfs, and re-created that segment again, and Windows
>> came back in pristine condition.  So that pretty much means my next
>> battle is Debian's package manager not liking my local repository (I
>> can't connect my Xen system to the internet, so I have to use such a
>> setup).  As that's how the Xen LiveCD scripts are doing things, and
>> assuming everything can be fetched online.
>> Some things I have noticed, though:
>> - After detaching a loopback device, there seems to be a delay in
>> when the kernel actually notices that it's detached.  If one does
>> losetup -d <loop> followed by losetup <loop> <new img>, it seems
>> like in a few cases, the kernel still thought it was looking at the
>> older loop attachment.  I ran into this when using loopback to look
>> at the disk at the disk level, and then passing -o 32256 to losetup
>> to look strictly at the first/primary NTFS partition (while trying
>> to clone it to a smaller disk image, which I finally gave up on
>> doing).
>> - Haven't found the cause just yet, but dmsetup sometimes doesn't
>> like looking at loopback devices, and possibly per the first item,
>> refuses to create the mapped device, citing a resource is busy.
>> Reboot fixes this, and I suspect both of these are caused by all the
>> experimenting I'm doing with switching between the various
>> loopbacks, I probably confuse the kernel.  From a scripted
>> standpoint, it should be a non-issue, though.
>> - Only tested this entire idea/setup against Windows XP.  It seems
>> to be fine, and that generally means any other OS as a domU should
>> work fine as well (because NTFS is by far the pickiest, most
>> temperamental FS known).  You get way more options with Linux/Other
>> UNIXes as far as tricking them into thinking they're in a r/w world,
>> but this can be extended to encapsulate quite a few domU's.
>> However, the only limitation I can see is the number of loopback
>> interfaces.  I use three to setup the Windows domU: /dev/loop2 for
>> the squashfs mount, /dev/loop0 for the windows image inside the
>> squashfs mount, and /dev/loop1 for the scratch area.  I think more
>> loop devices can be easily created, but I've not experimented that
>> far just yet...
>> That's all for now...I've got to install my network scanner into
>> this Windows image and re-clean it and run these tests all over
>> again.
>> Cheers!
>> --J
>> From: Thiago Camargo Martins Cordeiro [thiagocmartinsc@xxxxxxxxx]
>> Sent: Tuesday, August 18, 2009 11:29 PM
>> To: Joshua Kinard
>> Cc: xen-users@xxxxxxxxxxxxxxxxxxx
>> Subject: Re: [Xen-users] Bootable LiveDVD w/ Xen that boots Windows
>> Image?
>> This procedure will be in the next release of the Xen Live CD!!
>> qcow2 and LVM CoW snapshot for saving storage space while providing
>> fast domU creation from RW snapshots.... good for Eucalyptus, I
>> guess!
>> 2009/8/18 Joshua Kinard <joshua.kinard@xxxxxxxxxxxxx>
>> Think I cracked it.  Don't even need to deal with qemu's qcow stuff
>> (so far).  Still more tests pending (including using read-only drive
>> mounts).  But assume the following steps in a dom0:
>> - mkdir /windows
>> - cd /windows
>> - dd if=/dev/zero of=xp.img bs=1024k count=1 seek=7168
>> - touch xp.cfg
>> - nano xp.cfg
>> - <edit xp.cfg, setup as desired>
>> - xm create xp.cfg
>> - <install WinXP, patch, delete garbage, defrag, zero-out free
>> space, then shutdown>
>> - xm list (verify domU is actually dead)
>> Now after this, xp.img will contain a baseline WinXP install.  In my
>> specific case, I compacted everything down to ~2GB total installed
>> (inside the domU that is) by using straight qemu-emulated devices
>> (not the GPLPV stuff), no page file or hibernation, stripping nearly
>> every misc utility, and a bunch of other stuff, but NO NTFS
>> compression (for now, at least).
>> Next:
>> - dd if=/dev/zero of=xp_scratch.img bs=1024k count=1 seek=2048
>> - losetup /dev/loop0 xp.img
>> - losetup /dev/loop1 xp_scratch.img
>> - echo 0 $(blockdev --getsize /dev/loop0) snapshot /dev/loop0 /dev/
>> loop1 n 64 | dmsetup create xpcow
>> This maps our baseline WinXP image (xp.img) to /dev/loop0 and a
>> scratch area to /dev/loop1 (I don't even know if this is needed just
>> yet).  Needed because dmsetup only works with block devices.  Using
>> dmsetup, a snapshot is created, so that all writes to loop0 get
>> redirected to loop1, and creates a device, /dev/mapper/xpcow.
>> Edit xp.cfg to use phy:/dev/mapper/xpcow,hda,w, and boot Windows:
>> - xm create xp.cfg
>> In Windows, create a dummy file on the desktop or three, then
>> shutdown.  Re-start the domU and back at the desktop, we see that
>> the newly-created files still exist, so shutdown again.  Now:
>> - dmsetup remove /dev/mapper/xpcow
>> - losetup -d /dev/loop1
>> - dd if=/dev/zero of=xp_scratch2.img bs=1024k count=1 seek=2048
>> - losetup /dev/loop1 xp_scratch2.img
>> - echo 0 $(blockdev --getsize /dev/loop0) snapshot /dev/loop0 /dev/
>> loop1 n 64 | dmsetup create xpcow
>> - xm create xp.cfg
>> Back at the desktop, the newly-created files are now gone!
>> I did it this way as a manual test, because I'm veryifying a few
>> things:
>> a. Simulating the effect of creating the scratch image in a /tmpfs
>> mount, while the baseline image will be on a physical, read-only
>> medium.  By removing the mapped device and changing out the scratch
>> file, I was seeing whether the XP image would indeed revert to the
>> baseline state, to simulate a reboot in which /tmpfs is cleared.
>> Supposedly, the 'n' parameter to dmsetup does this anyways, but I
>> wanted to be doubly sure.
>> b. Need to scriptify the whole mess, since the baseline image will
>> already be pre-configured, the generation of the scratch image,
>> setup of the loop devices, and the device-mapping will be on-the-fly
>> when some future CD Image I put together boots up.
>> c. Avoids all the problems I see on Google about using blktap with
>> qcow with gplpv and such.  I'm probably not grasping some of it, but
>> I think those references are aiming for different uses.  So far,
>> this setup mostly relies wholly on the Linux dom0 to piece
>> everything together, leaving the WinXP domU utterly oblivious to
>> what is going on.  And given Windows' nature, that's exactly what we
>> want.
>> Performance isn't an issue for me in this, so I'm sure on a CD, this
>> will be slower than running Oracle on an 8086 (pretend for a moment
>> that this is actually possible), but if it works, and WinXP doesn't
>> complain, then all is good.
>> Thoughts?
>> ________________________________________
>> From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx
>> ] On Behalf Of Joshua Kinard [joshua.kinard@xxxxxxxxxxxxx]
>> Sent: Monday, August 17, 2009 9:50 AM
>> To: xen-users@xxxxxxxxxxxxxxxxxxx
>> Subject: RE: [Xen-users] Bootable LiveDVD w/ Xen that boots Windows
>> Image?
>> Hmm, block-level copy-on-write?  If qcow supports this out-of-the-
>> box, then I technically don't need any kind of UnionFS?  Just
>> someway to specify to Xen a read-only image with a qcow2 image in a
>> writable zone?
>> Going to dredge through some EU software patent I dug up from
>> Microsoft.  Supposed to document the /MININT switch to the NT kernel
>> that supposedly makes Windows write all registry changes to volatile
>> memory instead of to the registry hives.  It's mostly used in the
>> WinPE environment, but it looks like BartPE leverages it too.  Seems
>> I need more to it, though, than just modifying boot.ini to pass it,
>> as once I started to boot Windows from a read-only drive mount
>> (after discovering Xen/qemu don't properly honor the mode bit in the
>> Xen config for r or r/w, and even file-level permissions), Windows
>> crashed with UNMOUNTABLE_BOOT_VOLUME as its error.  But it
>> highlights the capability is there....just not easy.
>> USB is out, unfortunately, too.  For security reasons, we ban USB/
>> Firewire drives here, with the exception of CD Burners.  Ditto on
>> memory cards (SD, MMC, etc..).  I've got very narrow operating
>> parameters to work in, which is why this is proving to be quite a
>> fun challenge.
>> Thanks!,
>> --J
>> ________________________________________
>> From: Fajar A. Nugraha [fajar@xxxxxxxxx]
>> Sent: Friday, August 14, 2009 4:53 AM
>> To: Joshua Kinard
>> Cc: xen-users@xxxxxxxxxxxxxxxxxxx
>> Subject: 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.
>> --
>> Fajar
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