Re: [Xen-users] pygrub howto (Was:PV guest kernel location)

[Gregory Gee <gregory.gee@xxxxxxxxxxxx>]

 Well, since nobody answered, I'll do it myself.  With much pain and 
suffering of trial and error, I figure it out.  Turns out, it is the 
very well undocumented feature called pygrub.  The following is how I 
converted my PV guest mentioned below into having its own kernel and 
pygrub boot.
 My host system is running Xen 3.0.4 x86_64 on Ubuntu 6.06.  Soon to be 
3.1.0.  My guests are all x86_64 Ubuntu 6.06 as well.
**** FROM THE PV GUEST ****
1. First, I downloaded the tarballs for xen 3.0.4 and 3.1.0 for x86_64 
(since my guests were x86_64).
xen-3.0.4_1-install-x86_64.tgz
xen-3.1.0-install-x86_64.tgz

2. Remove/rename the old /lib/modules/2.6.16.33-xen, which was my kernel 
from 3.0.4 install.
3. Run the install.sh for each.

4. Create a file called /boot/grub/menu.lst with the following.

default         2
timeout         5

title           Ubuntu, memtest86+
root            (hd0,0)
kernel          /boot/memtest86+.bin
boot

title           Xen 3.0.4 vmlinuz-2.6.16.33-xen
root            (hd0,0)
kernel          /boot/vmlinuz-2.6.16.33-xen root=/dev/hda1 ro splash
savedefault
boot

title           Xen 3.1.0 vmlinux-syms-2.6.18-xen
root            (hd0,0)
kernel          /boot/vmlinux-syms-2.6.18-xen root=/dev/hda1 ro splash
savedefault
boot

5. shutdown -h now

**** FROM THE HOST ***
6. Change the cfg file below to look like this.  Remove all kernel stuff 
and add bootloader.
#  -*- mode: python; -*-
memory = 256
name = "mail"
vif = ['bridge=xenbr0']
disk = 
['file:/vserver/mail/guest_base2G.img,hda1,w','file:/vserver/mail/guest_swap256M.img,hda2,w','phy:data/mail,hda3,w']
bootloader = '/usr/bin/pygrub'

7. Start the new domU.
 xm create -c xmguest-mail

*******

 That's it.  It's nice that the domU has it's own copy of the kernel 
now and doesn't boot the kernel hosted on the host filesystem.  Also, it 
will make it easier if I have to move this domU to another system.
 I did run into one strange problem.  When I first ran the 'xm create' 
for each domU I converted, it failed saying 'nothing returned'.  I found 
that strange, but when I tried the 2nd time for each, it worked.  I hope 
it has nothing to do with running Xen 3.1.0 guests from pygrub on 3.0.4 
host.
 Hope people find this useful.  I wish there was more info on this 
topic from people that know how this works.  Also more info on the 
difference between file backed file: compared to tap:aio:.
Greg


Gregory Gee wrote:
>  Still new at this and was wondering if someone could give me some 
> pointers.  I have Xen 3.0.4 running great with 5 PV guests.  I just 
> followed setup instructions from a few wiki pages.  But the one thing 
> I noticed, is that the guest kernel is on the host.  Below is the cfg 
> file for my mail server guest.
> #  -*- mode: python; -*-
> kernel = "/boot/vmlinuz-2.6.16.33-xen"
> ramdisk = "/boot/initrd.img-2.6.16.33-xen"
> memory = 256
> name = "mail"
> vif = ['bridge=xenbr0']
> disk = 
> ['file:/vserver/mail/guest_base2G.img,hda1,w','file:/vserver/mail/guest_swap256M.img,hda2,w','phy:data/mail,hda3,w'] 
>
> ip = "192.168.10.43"
> netmask = "255.255.255.0"
> gateway = "192.168.10.1"
> hostname = "mail"
> root = "/dev/hda1 ro"
> extra = "4"
>
>  I see post talking about 32bit guests on 64bit hosts.  How do you do 
> that?  My main question is, how can I create a PV guest that is self 
> contained for files?  I want to pick up my guest and move it to 
> another system without worrying if the same kernel is available on the 
> new host.  I can't seem to find a wiki that gives these types of 
> instructions.
>  Can the kernel be copied into the guest and the guest boot from those 
> file?  How would my above cfg change?
> Thanks in advance for any help provided.
> Greg
>
>
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