I am trying to setup a Paravirtualization debian ubuntu guest image using centos 5.5 the thing that I don't understand is the media url

How would I setup a media url ? or is there a public one I could use

thanks

why would you want to do paravirtualisation? You should want from hyperthreading assuming your hardware supports it. What "media url" are you looking at? If you're booting from a network using kvm / qemu then this can be a simple nfs connection if you are using a network install, but moreover you have the option for an iso image, so you would want that for a first attempt.

so in Centos if you use the vitalization manager

go to page 39
http://www.centos.org/docs/5/html/5....ualization.pdf

it will ask for a media url

I am wondering if you can setup a ubuntu file system to install from a media url like centos so I can install a PV virtual machine.

From what I've been reading a Linux kernel that is "virtual aware" has better performance over a non "virtual aware system"

I am just curious about how I would create my own PV kernel and how I would create my own PV image.

like http://www.stacklet.com/

Like the manual says, you have to download an .iso file for debian or ubuntu paravirtualized installation, mount it via loopback and extract the contents to a directory.
Now, make that directory available via nfs, http or ftp.
Point virtual manager to the url from your server.

That's about what it says on page 38 of the .pdf manual you provided.

Which part was confusing to you?

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Again, you don't want paravirtualization if you can avoid it.

Care to explain why?

Because most modern cpus will support hyperthreading and so allow a better level of support from the hardware, rather than processing much of the work in software.

And how does hyperthreading help the OP isolating debian / ubuntu from his centos system?
He's right to look at paravirtualization, IMO.

As I recall the installation process within libvirt-manager and qemu if hyperthreading is not enabled within a bios then you'll not have the option to run kvm vm's i.e. qemu-kvm only vm's without direct cpu access. This means that, as per the wikipedia article only a subset of specifically ported guest os's can run, and they require an abstracted software layer on the host to map the resources, but HT and association extensions allow direct cut through with the guest running directly against the hardware and not needing to be aware of it's vm status at all for those forms of operations.

Also given the style of question being asked I'm inclined to think that this level of subtlety is not actually required and the OP just wants to get a vm going. The doc originally referenced is about achieving improved virt with xen, which is no longer the preferred vm mechanism and kvm.

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so I downloaded an iso then mounted the iso to /var/www/html/distro made if available by http://x.x.x.x/distro/

and I get this error.

unable to complete install 'exceptions.ValueError Could not find an installable distribution at 'http://x.x.x.x/ubuntu/'
Traceback (most recent call last):
File "/usr/share/virt-manager/virtManager/create.py", line 724, in do_install
dom = guest.start_install(False, meter = meter)
File "/usr/lib/python2.4/site-packages/virtinst/Guest.py", line 539, in start_install
self._prepare_install(meter)
File "/usr/lib/python2.4/site-packages/virtinst/Guest.py", line 594, in _prepare_install
meter = meter)
File "/usr/lib/python2.4/site-packages/virtinst/DistroInstaller.py", line 245, in prepare
self._prepare_kernel_and_initrd(guest, distro, meter)
File "/usr/lib/python2.4/site-packages/virtinst/DistroInstaller.py", line 194, in _prepare_kernel_and_initrd
type=self.os_type, distro=distro)
File "/usr/lib/python2.4/site-packages/virtinst/OSDistro.py", line 156, in acquireKernel
scratchdir, type, distro)
File "/usr/lib/python2.4/site-packages/virtinst/OSDistro.py", line 136, in _acquireMedia
scratchdir=scratchdir, arch=arch)
File "/usr/lib/python2.4/site-packages/virtinst/OSDistro.py", line 100, in _storeForDistro
raise ValueError, _("Could not find an installable distribution at '%s'" %
ValueError: Could not find an installable distribution at 'http://x.x.x.x/ubuntu/'

so its better to have Xen Full virtualization (HVM) than Xen Paravirtualization (PV)?

I am confused? from everything I've read PV should run better than HVM.

I am just experimenting, but would like to know what is the best to use for visualizing linux distros for optimal performance.

http://wiki.xensource.com/xenwiki/XenOverview

thanks

centos 5.5 uses kvm as default, not Xen. Why are you referring to xen? Do you specifically want to use it?

As for performance, everything going through software interfaces can (surely??) only have an ultimately detrimental effect.

I am not sure exactly what the difference between xen and kvm is exactly but I've been using the

xm list
xm create

commands to view and console into vm's and I didn't install kvm during the install process so I am fairly certain I am using xen.

dose kvm have domU?

anyway from what I've been reading hvm uses more software to emulate the the true hardware while I know it does get a bost from the VT technology in the cpu. I am not sure if HVM has better performance than pv where a PV kernel passes its request directly to the xen kernel.