Xen users - Oct 2012 - possible newbie-level question - updating kernels?

Forgive me for asking, but I can''t seem to find the answer elsewhere 
sifting though the chaff of Google and whatnot.  I''m running Xen 4.1.2 
on Ubuntu server 12.04.1 LTS.  How do I go about updating the kernel 
(and perhaps more importantly the modules that go with it) in a DomU to 
match what the Dom0 is running?
My Dom0 is currently at 3.2.0-31-generic #50, but I have at least one 
DomU at 3.2.0-29-generic #46.

-Robert

On Thu, Oct 4, 2012 at 8:59 AM, Robert Rust <robert@digitalsilk.net>
wrote:
> Forgive me for asking, but I can''t seem to find the answer
elsewhere sifting
> though the chaff of Google and whatnot.  I''m running Xen 4.1.2 on
Ubuntu
> server 12.04.1 LTS.  How do I go about updating the kernel (and perhaps
more
> importantly the modules that go with it) in a DomU to match what the Dom0
is
> running?
You don''t.

Or to be accurate, if you set it up correctly, domU''s kernel version
can be completely different from what dom0 is running. Even different
OS (e.g. solaris).

There are many ways to load domU kernel. In the old days, domU runs
whatever dom0 is running. Currently you can let domU load its own
kernel by setting domU config file to use bootloader (pygrub), or to
use a "kernel" from dom0 that can "chainload" another kernel
from domU
(pv-grub). Once you set that up, then do whatever you normally do to
update the kernel (e.g. apt-get update;apt-get dist-upgrade)

-- 
Fajar

Robert Rust wrote:
>How do I go about updating the kernel (and perhaps more importantly 
>the modules that go with it) in a DomU to match what the Dom0 is 
>running?
As Fajar says, just don''t !

Use a different kernel for your DomU than used for Dom0.
Some of my guests use Pygrub without problem. Others have problems 
and won''t boot - so for those I just copy the kernel and initrd* to a 
folder on Dom0 alongside the guest config file and use the boot= and 
root= lines as you are probably doing now. This latter method does 
mean you have to copy one or two files (and possibly update the 
config file) whenever you update the kernel or do anything else that 
updates the initrd - but at least you are booting something that''s 
specific to the virtual machine.

* I used to use the shared Dom0 kernels until I twigged that this 
also meant I was using an initrd in the guest that was actually built 
for the Dom0.
The initrd is more machine specific than the kernel.

-- 
Simon Hobson

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