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

["Karsten M. Self" <karsten@xxxxxxxxxxxxx>]

Anthony Liguori wrote:

> Karsten M. Self wrote:
>
> > That's actually getting to be a preferred method here, at least for 
> > some folks.
> > qemu file-backed installs allow you to use an existing RHEL 
> > installer, without much fuss or mess, the tricky bit is finding the 
> > filesystem afterward, as what qemu produces is a _partitioned_ file 
> > with filesystems within it.
>
> Or you can just expose as a device with a partition table.  IMHO, this 
> is the best approach.
> I've even had success resizing the disk image, and then (using a boot 
> disk), appropriately resizing the filesystem.
> > > 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.
> > Are you doing this with the qemu partitioned file itself?
>
> 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?

> >    volumes, though it's possible to do so, complicating matters
> >    somewhat more.
>    The first partition is /boot, the second is /.  I didn't use logical
> If you want to extract the filesystems, I'd recommend using lomount as 
> Ian suggests (and then just tar up the partitions).
Sure.  Diff'rent strokes for diff'rent folks...[1]

> > 5. Loopback mount the qemu images, creating a couple of mountpoints.
> >    Using the file I'm referencing above (rhel4):
> >
> >        mkdir mp1 mp2
> >        su -c 'mount -o loop,offset=$(( 63 * 512 )) -t ext3 rhel4 mp1'
> >        su -c 'mount -o loop,offset=$(( 4192964 * 512 )) -t ext3 rhel4 
> > mp2'
> > As a final step, you could copy the contents of these two mountpoints
> > into a partition or a single filesystem image (a file with just a
> > filesystem in it, no partitions) which can be used for a Xen file-backed
> > DomU, etc.
>
> 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?

I'm running RHEL4 and after /etc/fstab, relocating boot and modifying 
/etc/fstab, commenting out the MAC address, it seems happy.
> 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.
See RH Bugzilla:

https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=150206
https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=150946

> QEMU is a pretty amazing little piece of software :-)
Innit just?  Spread the word, brother ;-)


Cheers.

--------------------
Notes:

1.  ObGaryColeman, showing my age.  Wait!  I tuned in, but I didn't watch...

--
Karsten M. Self <karsten@xxxxxxxxxxxxx>
XenSource, Inc.
2300 Geng Road #250                                +1 650.798.5900 x259
Palo Alto, CA 94303                                +1 650.493.1579 fax


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