Re: [Xen-users] difference between Xen and Dom0 kernel

["Fajar A. Nugraha" <fajar@xxxxxxxxx>]

On Thu, Nov 12, 2009 at 5:44 PM, Tapas Mishra <tapas@xxxxxxxxxxxx> wrote:
> Thanks for your reply .
> From your reply what I inferred is that to be able to use
> virtualization from XEN
> I need to install Hypervisor
> Xen tools and then I can start working on like installing guest
> operating systems
> in the installed hypervisor.

pretty much.

> Say for example I am having a laptop with Ubuntu installed.

The easiest way is tu start with RHEL/Centos5, and run "yum install
xen kernel-xen". After that you just edit /boot/grub/menu.lst to
choose newly installed kernel/hypevisor, reboot, and you're ready to
go.

Once you have that working and able to start some domUs, you can try
compiling xen and kernels manually if you like.


> So I need to install Xen Hypervisor on it and
> then install a Dom0 kernel assuming that ( I downloaded the source
> hypervisor without linux-2.6.18 )
> from http://www.xen.org/products/xen_source.html

http://bits.xensource.com/oss-xen/release/3.4.2/xen-3.4.2.tar.gz will
get you the source for xen hypervisor and userland. However, if you
run "make" (or make world) it will download the kernel as well. If you
only want to compile the hypervisor and userland, look at the included
README and Makefile.

> then I need to compile one Dom0 kernel as per the instructions given
> http://wiki.xensource.com/xenwiki/XenParavirtOps

If you just run make you'd automatically get 2.6.18 kernel. I suggest
you start with that first.
The wiki page is useful if you want to compile newer pv_ops kernel.

> What does the following command do ?
> git clone git://git.kernel.org/pub/scm/linux/kernel/git/jeremy/xen.git
> linux-2.6-xen

That will download newest pv_ops kernel with xen support.

>
> Or I need to download a kernel from www.kernel.org and compile it so
> that I can use it as Dom0

vanilla kernel can't be used as dom0 kernel yet. You can use it as
domU kernel though.

> why can I not use the kernel present on my
> laptop in the installed Ubuntu as Dom0 and after installing hypervisor
> start working on it.

Because dom0 kernel needs to have xen support. Ubuntu's kernel does
not have that yet.
Jeremy's git tree (the git command you mentioned) has it.


> To be able to install hypervisor what do I need to do.

See what I wrote about RHEL/Centos and README/Makefile.

-- 
Fajar

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