Xen users - Sep 2008 - Xen 3.3 hypervisor with stock dom0 kernel from Debian Etch?

Hi.

a) Is it possible to use the stock Xen/dom0 kernel from Debian Etch [1] 
with the Xen 3.3 hypervisor?

b) If a), is it advisable at all?

c) If b), is this difficult to achieve or can I just to compile the 
hypervisor from source [2]?

Best regards,
Henrik

[1] http://packages.debian.org/etch/linux-image-2.6.18-6-xen-686
[2] http://bits.xensource.com/oss-xen/release/3.3.0/xen-3.3.0.tar.gz

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Hello Henrik :)

On Wed, 2008-09-24 at 12:46 +0200, xen-users@henrik.synth.no
wrote:
> Hi.
> 
> a) Is it possible to use the stock Xen/dom0 kernel from Debian Etch [1] 
> with the Xen 3.3 hypervisor?
> 
> b) If a), is it advisable at all?
> 
> c) If b), is this difficult to achieve or can I just to compile the 
> hypervisor from source [2]?
I can only advise the following:

1 - When using something other than the official XenLinux 2.6.18,
    ensure that you do proper regression tests prior to putting it
    in production. This means, take a 64 bit dom-0, mix 32/64 bit 
    guests and hammer the guests for some time, or vice-versa.

2 - Building at least the HV and tools from source is desirable. 
    While some distributions apply some measure of sanity prior to
    releasing their patched versions, not all do.

3 - If you use some distributions xen-0 kernel that is newer than the
    official XenLinux kernel, ensure that it will be supported until
    dom-0 operations appear in mainstream Linux.

Many of us are now caught with ad-hoc 2.6.24 xen-0 patched kernels in
production, this is a nightmare that you can escape with a bit of
diligence.

Cheers,
--Tim



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On 24-09-08 13:44, Tim Post wrote:
 > Hello Henrik :)

Hi Tim, thanks for your swift answer!
> On Wed, 2008-09-24 at 12:46 +0200, xen-users@henrik.synth.no wrote:
>> a) Is it possible to use the stock Xen/dom0 kernel from Debian Etch [1]
>> with the Xen 3.3 hypervisor?
 >
> 1 - When using something other than the official XenLinux 2.6.18,
>      ensure that you do proper regression tests prior to putting it
>      in production. This means, take a 64 bit dom-0, mix 32/64 bit
>      guests and hammer the guests for some time, or vice-versa.
Debian Etch has stayed with 2.6.18 for their Xen dom-0 kernels, I 
believe they should be OK.
>> b) If a), is it advisable at all?
 >
> 2 - Building at least the HV and tools from source is desirable.
>      While some distributions apply some measure of sanity prior to
>      releasing their patched versions, not all do.
The Debian packaged HV and tools in Debian are on Xen 3.2.  If I 
understand you correctly, I should be able to use the same kernel and 
just build the HV and tools?  There aren''t any required kernel changes
between 3.2 and 3.3 from Xen?
>> c) If b), is this difficult to achieve or can I just to compile the
>> hypervisor from source [2]?
>
> 3 - If you use some distributions xen-0 kernel that is newer than the
>      official XenLinux kernel, ensure that it will be supported until
>      dom-0 operations appear in mainstream Linux.
OK, I might be able to stick with the Debian kernel then.
> Many of us are now caught with ad-hoc 2.6.24 xen-0 patched kernels in
> production, this is a nightmare that you can escape with a bit of
> diligence.
Sounds like a nightmare indeed.  And according to the xensource wiki 
[3], dom0 won''t even be in 2.6.27.

Best regards,
Henrik

[3] http://wiki.xensource.com/xenwiki/XenParavirtOps


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Tim,

 Have you setup "nosmp" option in your 2.6.24 kernel xen ?

Regards,
Thiago

2008/9/24 Tim Post <echo@echoreply.us>
> Hello Henrik :)
>
> On Wed, 2008-09-24 at 12:46 +0200, xen-users@henrik.synth.no wrote:
> > Hi.
> >
> > a) Is it possible to use the stock Xen/dom0 kernel from Debian Etch
[1]
> > with the Xen 3.3 hypervisor?
> >
> > b) If a), is it advisable at all?
> >
> > c) If b), is this difficult to achieve or can I just to compile the
> > hypervisor from source [2]?
>
> I can only advise the following:
>
> 1 - When using something other than the official XenLinux 2.6.18,
>    ensure that you do proper regression tests prior to putting it
>    in production. This means, take a 64 bit dom-0, mix 32/64 bit
>    guests and hammer the guests for some time, or vice-versa.
>
> 2 - Building at least the HV and tools from source is desirable.
>    While some distributions apply some measure of sanity prior to
>    releasing their patched versions, not all do.
>
> 3 - If you use some distributions xen-0 kernel that is newer than the
>    official XenLinux kernel, ensure that it will be supported until
>    dom-0 operations appear in mainstream Linux.
>
> Many of us are now caught with ad-hoc 2.6.24 xen-0 patched kernels in
> production, this is a nightmare that you can escape with a bit of
> diligence.
>
> Cheers,
> --Tim
>
>
>
> _______________________________________________
> Xen-users mailing list
> Xen-users@lists.xensource.com
> http://lists.xensource.com/xen-users
>

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2008/9/24  <xen-users@henrik.synth.no>:
> Hi.
>
> a) Is it possible to use the stock Xen/dom0 kernel from Debian Etch [1]
with
> the Xen 3.3 hypervisor?
The Debian xen kernel (amd64) works fine for me as both dom0 and domU with 3.3.

The Debian kernels support my hardware a lot better though that the
standard config of the xensource kernels (more modules enabled etc).
>
> b) If a), is it advisable at all?
Advisable? I dunno, but I haven''t had much luck getting the xensource
kernels working well at all well on Debian Etch (see other recent
thread). The combined dom0/domU xensource kernel works OKish as a dom0
but not as a PV domU, and I can''t get the separate dom0 and domU
kernels working at all. I''m still trying (not very successfully) to
get them working though, but my kernel building / initrd
troubleshooting skills are only average at best.

The Debian kernel at least has the advantage of security updates via
aptitude/apt-get.
> c) If b), is this difficult to achieve or can I just to compile the
> hypervisor from source [2]?
You can compile the 3.3 hypervisor and all the tools from source (it
worked for me), and still use the standard Debian kernel for
dom0/domU.

-- 
Cheers
Anton

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On 25 Sep 2008 11:44:39 +1200, Anton wrote:
> The Debian xen kernel (amd64) works fine for me as both dom0 and domU with
3.3.
>
> The Debian kernels support my hardware a lot better though that the
> standard config of the xensource kernels (more modules enabled etc).
Thanks a lot, this is great news.
>> b) If a), is it advisable at all?
>
> Advisable? I dunno, but I haven''t had much luck getting the
xensource
> kernels working well at all well on Debian Etch (see other recent
> thread). The combined dom0/domU xensource kernel works OKish as a dom0
> but not as a PV domU, and I can''t get the separate dom0 and domU
> kernels working at all. I''m still trying (not very successfully)
to
> get them working though, but my kernel building / initrd
> troubleshooting skills are only average at best.
Just out of curiosity:  Are there any reasons why you want the xensource 
kernel when the debian kernel works OK?
>> c) If b), is this difficult to achieve or can I just to compile the
>> hypervisor from source?
>
> You can compile the 3.3 hypervisor and all the tools from source (it
> worked for me), and still use the standard Debian kernel for
> dom0/domU.
Super!  How about using the debian lenny 2.6.26 domU kernel [1] on top 
of the debian etch 2.6.18 dom0 kernel [2] (with Xen 3.3)?  I guess that 
would work?

And my last silly question: Are there any real benefits on using a 64 
bit dom0 [3] when I am only serving 32 bit debian domU''s?

(I''m sorry for my detailed questions -- I am setting up a xen server 
tomorrow and merging a stand-alone server to it, and my setup time is 
severely limited.)

Best regards,
Henrik

[1] http://packages.debian.org/lenny/linux-image-2.6.26-1-xen-686
[2] http://packages.debian.org/etch/linux-image-2.6.18-6-xen-686
[3] http://packages.debian.org/etch/linux-image-2.6.18-6-xen-amd64

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2008/9/25  <xen-users@henrik.synth.no>:
> Just out of curiosity:  Are there any reasons why you want the xensource
> kernel when the debian kernel works OK?
Just a nagging feeling that the newest xensource kernels are more up
to date and suitable for Xen 3.3 - eg some of the new 3.3 (or even 3.2
and 3.1 for that matter) features might rely on code that isn''t in the
Debian kernel. But nothing definite, as I don''t know enough about the
potential changes.
> Super!  How about using the debian lenny 2.6.26 domU kernel [1] on top of
> the debian etch 2.6.18 dom0 kernel [2] (with Xen 3.3)?  I guess that would
> work?
Should do. The Lenny domU kernel would need to use the native
paravirtual ops stuff though - I haven''t tried that yet myself. pvgrub
sounds like a good way to manage a Lenny domU kernel with an Etch dom0
kernel.
>
> And my last silly question: Are there any real benefits on using a 64 bit
> dom0 [3] when I am only serving 32 bit debian domU''s?
Not sure - maybe if you want to run a 64bit domU in the future?. If
you can get all your memory recognised by the 32bit dom0, there might
be some advantages to using 32bit for both. Apparently you used to
need the same arch for both dom0 and domU to get certain
save/restore/migrate type features working, but I think 3.3 doesn''t
have that limitation anymore. Also using the same arch for dom0 and
domU would make it easy for aptitude to update kernels for both (as
they''d share it), but with 3.3 pvgrub lets the domUs manage their own
kernels*, so that advantage goes away too (I think).

* yeah I know pygrub could do that too but it was a bit ugly, and
Debian never really embraced pygrub like RH/Suse did anyway.

But I''m a little fuzzy on all these details, so you''d want to
get more
advice and/or test it yourself :)

-- 
Cheers
Anton

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On 24-09-08 12:46, xen-users@henrik.synth.no wrote:
> a) Is it possible to use the stock Xen/dom0 kernel from Debian Etch 
> [1] with the Xen 3.3 hypervisor?
>
> b) If a), is it advisable at all?
>
> c) If b), is this difficult to achieve or can I just to compile the 
> hypervisor from source [2]?
In case anyone is interested: I ended up going the safe route.   I 
installed Debian lenny on the dom0 and domU, used the 2.6.18 kernel from 
etch on both, and the 3.2.1 hypervisor from lenny.  It works like a charm!

Anyway, thanks for all info!

Henrik


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xen-users@henrik.synth.no writes:
> On 24-09-08 12:46, xen-users@henrik.synth.no wrote:
>> a) Is it possible to use the stock Xen/dom0 kernel from Debian Etch
>> [1] with the Xen 3.3 hypervisor?
>>
>> b) If a), is it advisable at all?
>>
>> c) If b), is this difficult to achieve or can I just to compile the
>> hypervisor from source [2]?
>
> In case anyone is interested: I ended up going the safe route.   I
> installed Debian lenny on the dom0 and domU, used the 2.6.18 kernel
> from etch on both, and the 3.2.1 hypervisor from lenny.  It works like
> a charm!
Have you had any problem using the Lenny kernel in domU?
-- 
Thanks,
Feri.

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On 29-09-08 11:43, Ferenc Wagner wrote:
> xen-users@henrik.synth.no writes:
>> In case anyone is interested: I ended up going the safe route.   I
>> installed Debian lenny on the dom0 and domU, used the 2.6.18 kernel
>> from etch on both, and the 3.2.1 hypervisor from lenny.  It works like
>> a charm!
>
> Have you had any problem using the Lenny kernel in domU?
I planned to use the domU kernel from lenny (2.6.26), but I never got 
around to actually try it.   It shouldn''t be a problem, though, since 
the Debian wiki [1] recommends it.

Henrik

[1] http://wiki.debian.org/Xen#head-21b571d5f81b6a36a5af19cfc7439045c3fb5b20

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