Xen users - May 2010 - Question: Best option to run an Arch Linux DomU

Hello,

I understand that one could create a HVM domU to install a great deal of various
operating systems for testing purpose. On my particular Xen server I am running
some debian DomUs as well but they are running as PV domUs, by using a
configuration found at:

http://people.debian.org/~joeyh/d-i/images/daily/netboot/xen/xm-debian.cfg


What options would I have to setup an Arch Linux DomU?

And what options would yield best performance? What steps could be taken to run
Arch Linux as a PV domU?

Thanks.

 

-M


 		 	   		  
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On Tue, May 11, 2010 at 8:58 AM, Mike Viau <viaum@sheridanc.on.ca>
wrote:
> Hello,
>
> I understand that one could create a HVM domU to install a great deal of
> various operating systems for testing purpose. On my particular Xen server
I
> am running some debian DomUs as well but they are running as PV domUs, by
> using a configuration found at:
>
> http://people.debian.org/~joeyh/d-i/images/daily/netboot/xen/xm-debian.cfg
>
>
> What options would I have to setup an Arch Linux DomU?
You should ask archlinux guys if they support running as Xen domU first.
>
> And what options would yield best performance? What steps could be taken to
> run Arch Linux as a PV domU?
The general way to do that is to install as HVM domU, install
xen-commpatible kernel if necessary, then do some modifications. Most
ditros using recent-enough kernel 2.6 can be easily converted to PV
domU, but you might need to compile your own kernel package for that.

-- 
Fajar

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> Tue, 11 May 2010 11:15:03 +0700 <fajar@fajar.net> wrote:
> 
> >
> > What options would I have to setup an Arch Linux DomU?
> 
> You should ask archlinux guys if they support running as Xen domU first.
> 
I came across a wiki page from the Arch Linux guys and kick myself because for
their Dom0 documentation references Xen 2 binaries
(xen-2.0.7-install-x86_32.tgz)

http://wiki.archlinux.org/index.php/Xen_Install
> >
> > And what options would yield best performance? What steps could be
taken to
> > run Arch Linux as a PV domU?
> 
> The general way to do that is to install as HVM domU, install
> xen-commpatible kernel if necessary, then do some modifications. Most
> ditros using recent-enough kernel 2.6 can be easily converted to PV
> domU, but you might need to compile your own kernel package for that.
> 
Well I have no doubts (unless misinformed) that Arch Linux should run as PV domU
becasue I was told due to there rolling release mentaility they are usually
using the most up-to-date package. So in the sense of the Linux kernel they are
using the 2.6.33 branch which has domU support already.

Can you give me some examples on what you mean by "then do some
modifications"?

Lastly I don''t understand the domU configuration offered by the Arch
Linux Xen page:

  Creating a xenU instance 
  The /etc/xen file 
You need to create a domain configuration file for your xenU 
instance.

Here is a simple example. The useful comments have been removed. 
If you wish to delve deeper, the xmexample1 and xmexample2 files contain
 more information. Just copy them to a custom filename, and edit away.

Here is the example used for this how to:


#  -*- mode: python; -*-
#===========================================================================
# Kernel image file.
kernel = "/boot/vmlinuz-2.6.11-xenU"

# Initial memory allocation (in megabytes) for the new domain.
memory = 256

# A name for your domain. All domains must have different names.
name = "WebServer"

disk = [
''file:/home/xen/webserver,hda1,w'',''file:/home/xen/webserver-swap,hda2,w''
]

# Set root device.
root = "/dev/hda1 ro"

# Sets runlevel 4.
extra = "3"

restart = ''onreboot''

Name the file webserver for the purposes of this example. 
/etc/xen/webserver



How can one boot Arch Linux or any distro really without having that distro
already running to copy the system from right?
Is HVM install the only way?


Thanks.


-M
 		 	   		  
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On Tue, May 11, 2010 at 8:41 PM, Mike Viau <viaum@sheridanc.on.ca>
wrote:
> I came across a wiki page from the Arch Linux guys and kick myself because
> for their Dom0 documentation references Xen 2 binaries
> (xen-2.0.7-install-x86_32.tgz)
>
> http://wiki.archlinux.org/index.php/Xen_Install
They did give a warning that "This article or section is out of date."
:D
> Well I have no doubts (unless misinformed) that Arch Linux should run as PV
> domU becasue I was told due to there rolling release mentaility they are
> usually using the most up-to-date package. So in the sense of the Linux
> kernel they are using the 2.6.33 branch which has domU support already.
That depends. While the kernel supports it, it might not be enabled in
the config.
For example, Ubuntu Karmic''s 2.6.31-20-server kernel has these options
enabled which allows it to run as domU kernel

CONFIG_XEN=y
CONFIG_XEN_MAX_DOMAIN_MEMORY=32
CONFIG_XEN_SAVE_RESTORE=y
# CONFIG_XEN_DEBUG_FS is not set
CONFIG_XEN_BLKDEV_FRONTEND=m
CONFIG_XEN_NETDEV_FRONTEND=m
CONFIG_XEN_KBDDEV_FRONTEND=m
CONFIG_HVC_XEN=y
CONFIG_XEN_FBDEV_FRONTEND=m
CONFIG_XEN_BALLOON=y
CONFIG_XEN_SCRUB_PAGES=y
CONFIG_XEN_DEV_EVTCHN=m
CONFIG_XENFS=m
CONFIG_XEN_COMPAT_XENFS=y
CONFIG_XEN_SYS_HYPERVISOR=y
>
> Can you give me some examples on what you mean by "then do some
> modifications"?
One example, the console will change to hvc0 (for newer kernels) or
xvc0 (on older kernel-xen). The disk would also be recognized as xvda
instead of sda. And the required disk/network modules will change as
well. See  http://pastebin.com/f6a5022bf for example on converting
Centos domU.
>
> Lastly I don''t understand the domU configuration offered by the
Arch Linux
> Xen page:
>
To understand Xen domU config, it''d probably be easier to install a
distro that comes with Xen builtin (Centos, opensuse) and do one of
these:
- look at examples on /etc/xen/xmexample*
- create a domU using GUI like virt-manager, and look at the resulting
config file
> How can one boot Arch Linux or any distro really without having that distro
> already running to copy the system from right?
Don''t know about archilinux, but other distros can manage just fine.
The general method is to have a special kernel and initrd for
installation that is xen-compatible (like
http://mirrors.kernel.org/centos/5/os/x86_64/images/xen/), then
perform a network-based install (http, nfs, etc.)
> Is HVM install the only way?
No, but depending on your setup, it might be the easiest way.

-- 
Fajar

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