Xen users - Feb 2013 - Convert Debian 6 from HVM to PV

I have a couple Debian 6 HVM VMs. From what I''ve read, Debian
6''s
standard kernels have pv_ops already enabled. I''d like to convert these
to pv for the following reasons (Assuming both of are valid expectations):

1) so the VMs use pv for the NICs
2) so the VMs properly respond to shutdown/reboot commands from xm

I''m having trouble converting them. I believe need to convert the menu 
from something like this:
         root (hd0,0)
         kernel /xen.gz-2.6.18-53.1.14.el5
         module /vmlinuz-2.6.18-53.1.14.el5xen ro root=LABEL=/
         module /myinitrd.img

to something like this:
         root (hd0,0)
         kernel /vmlinuz-2.6.18-53.1.14.el5xen ro root=LABEL=/
         initrd /myinitrd.img

The Debian 6 VMs I have appear to use grub2, which is a pain in the rear 
as far as I can tell. I expect there are good reasons for it, but being 
able to modify a menu.lst makes this transition much easier. The top of 
the file says to use /etc/grub.d and settings from /etc/default/grub to 
update grub.cfg, but I can''t figure out how they build the menu
section.

Here''s the menu section of grub.cfg. Can anyone give me some help on 
changing this to the proper form for booting pv?

### BEGIN /etc/grub.d/10_linux ###
menuentry ''Debian GNU/Linux, with Linux 2.6.32-5-686'' --class
debian
--class gnu-linux --class gnu --class os {
         insmod part_msdos
         insmod ext2
         set root=''(hd0,msdos1)''
         search --no-floppy --fs-uuid --set 
8d0d1b45-e312-49ee-9213-50651e18f259
         echo    ''Loading Linux 2.6.32-5-686 ...''
         linux   /boot/vmlinuz-2.6.32-5-686 
root=UUID=8d0d1b45-e312-49ee-9213-50651e18f259 ro  quiet
         echo    ''Loading initial ramdisk ...''
         initrd  /boot/initrd.img-2.6.32-5-686
}

Any help is appreciated.

Thanks,
James

On Mon, 2013-02-25 at 15:24 +0000, James Pifer wrote:
> I''m having trouble converting them. I believe need to convert the
menu
> from something like this:
>          root (hd0,0)
>          kernel /xen.gz-2.6.18-53.1.14.el5
>          module /vmlinuz-2.6.18-53.1.14.el5xen ro root=LABEL=/
>          module /myinitrd.img
> 
> to something like this:
>          root (hd0,0)
>          kernel /vmlinuz-2.6.18-53.1.14.el5xen ro root=LABEL=/
>          initrd /myinitrd.img
This isn''t strictly necessary since pygrub will happily ignore the
first
xen.gz line and in any case this syntax is specific to RH, under Debian
in a guest with grub the entries will be similar to the second form
anyway.
> The Debian 6 VMs I have appear to use grub2, which is a pain in the rear 
> as far as I can tell. I expect there are good reasons for it, but being 
> able to modify a menu.lst makes this transition much easier. The top of 
> the file says to use /etc/grub.d and settings from /etc/default/grub to 
> update grub.cfg, but I can''t figure out how they build the menu
section.
update-grub runs the scripts under /etc/grub.d.
> Here''s the menu section of grub.cfg. Can anyone give me some help
on
> changing this to the proper form for booting pv?
> 
> ### BEGIN /etc/grub.d/10_linux ###
> menuentry ''Debian GNU/Linux, with Linux 2.6.32-5-686''
--class debian
> --class gnu-linux --class gnu --class os {
>          insmod part_msdos
>          insmod ext2
>          set root=''(hd0,msdos1)''
>          search --no-floppy --fs-uuid --set 
> 8d0d1b45-e312-49ee-9213-50651e18f259
>          echo    ''Loading Linux 2.6.32-5-686 ...''
>          linux   /boot/vmlinuz-2.6.32-5-686 
> root=UUID=8d0d1b45-e312-49ee-9213-50651e18f259 ro  quiet
>          echo    ''Loading initial ramdisk ...''
>          initrd  /boot/initrd.img-2.6.32-5-686
> }
This already looks correct, except you need to install the 686-bigmem
kernel flavour and not the -686 flavour to get Xen support.

Ian.

> This already looks correct, except you need to install the 686-bigmem
> kernel flavour and not the -686 flavour to get Xen support.
>
> Ian.
>
Ian,

Thanks for the quick response. If I understand you correctly, if I 
install 686-bigmem kernel then pygrub should happily boot it? Might be 
jumping the gun, but how do I make 686-bigmem the default after 
installing or will that happen automatically being the last kernel 
installed?

(yes, my example menu was from a centos machine)

Thanks again,
James

On Mon, 2013-02-25 at 15:39 +0000, James Pifer wrote:
> Thanks for the quick response. If I understand you correctly, if I 
> install 686-bigmem kernel then pygrub should happily boot it?
Yes.
> Might be  jumping the gun, but how do I make 686-bigmem the default after 
> installing or will that happen automatically being the last kernel 
> installed?
Well, I would uninstall the others.

But pygrub is interactive so you can just select the one you want. I
expect you could also set /etc/default/grub:GRUB_DEFAULT to the index of
the entry to boot. You can also pass --entry=N to pygrub via the
bootloader_args option in your guest configuration.

Ian.

On 2/25/2013 10:44 AM, Ian Campbell wrote:
> On Mon, 2013-02-25 at 15:39 +0000, James Pifer wrote:
>> Thanks for the quick response. If I understand you correctly, if I
>> install 686-bigmem kernel then pygrub should happily boot it?
> Yes.
>
>> Might be  jumping the gun, but how do I make 686-bigmem the default
after
>> installing or will that happen automatically being the last kernel
>> installed?
> Well, I would uninstall the others.
>
> But pygrub is interactive so you can just select the one you want. I
> expect you could also set /etc/default/grub:GRUB_DEFAULT to the index of
> the entry to boot. You can also pass --entry=N to pygrub via the
> bootloader_args option in your guest configuration.
>
> Ian.
>
Ian,

Worked great. Thanks for the help!

James