Re: [Xen-users] Guest O/S Questions

[Anthony Liguori <aliguori@xxxxxxxxxx>]

Karsten M. Self wrote:

> > > > dd skip=63 bs=512 if=qemu.img of=xen.img
> > > >
> > > > Keep in mind, I've not tried this myself :-)
> Doh!  I missed your skip.  That should work for a partitioned file 
> with a single partition.  If you've got multiple partitions, you'd 
> want to add the size in blocks as 'count', otherwise you're going to 
> have multiple partitions in what you're assuming is a single 
> filesystem image.  Somewhere down the road, something's probably going 
> to get confused, unhappy, or both, about that.  Or you're just going 
> to carry around a lot of slack space.
It's pretty straight forward to write a program to split a partitioned 
file into multiple single partition images.  I'm not sure it's the right 
use case though.
> > Yup.
> >
> > My xend config line looks like this:
> >
> > disk = [ 'file:/root/FC4.img,hda,w' ]
> > root = "/dev/hda1"
>
> > That just works.  There shouldn't be any disadvantage to using this 
> > method (other than it makes resizing individual partitions a bit more 
> > difficult).
>
> ... that's on a filesystem image, not a partitioned file, though, right?
No.  This is a partitioned file.  Xen will expose any file as a straight 
block device under any device number.  If you use the device number for 
a whole disk (in this case, hda--although hdb, sda, etc. would also 
work), linux will read the partition table during bootup (that is, the 
first 63 sectors of the disk) and create the appropriate partitions.
To reiterate, FC4.img is an unmodified QEMU raw device.  Furthermore, 
with qemu-img convert, you could convert a VMWare image to a QEMU raw 
image, and boot that directly in Xen using this method.
> > There's a few things you'll want to do once you do the QEMU install.  
> > Namely, you'll want to make sure to install the appropriate modules 
> > (and run depmod).
>
> Which modules?
Depends on your domU config I guess.  FC4 won't boot for me unless it 
finds a modules.dep for the appropriate kernel.
> > Otherwise, it just works.
> >
> > The next logical step is to run QEMU within a domU and automate the 
> > whole process.
>
> Actually, a decent RH bootstrap would be useful.  Dittos the ability 
> to install into an arbitrary target, *without* requiring a valid 
> bootable partition.
With QEMU + VNC under a domU, you can actually install directly into a 
domU I posted a link to a script to build a ramdisk that contains 
QEMU/VNC specifically for this purpose.
> > QEMU is a pretty amazing little piece of software :-)
>
> Innit just?  Spread the word, brother ;-)
We could definitely improve our collaboration with QEMU.   There's a lot 
of cool things you can do when you combine QEMU and Xen.
Regards,

Anthony Liguori

> Cheers.
>
> --------------------
> Notes:
>
> 1.  ObGaryColeman, showing my age.  Wait!  I tuned in, but I didn't 
> watch...

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