RE: [Xen-users] 32Bit DomU on 64Bit Dom0 possible?

["Petersson, Mats" <Mats.Petersson@xxxxxxx>]

> -----Original Message-----
> From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx 
> [mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of 
> Robin Schröder
> Sent: 07 February 2006 10:52
> To: xen-users@xxxxxxxxxxxxxxxxxxx
> Subject: Re: [Xen-users] 32Bit DomU on 64Bit Dom0 possible?
> 
> Patrick Meisel schrieb:
> > Hello list,
> > 
> > i am in the unfortunate position to have to install a 
> software on our 
> > Opteron xen machine which will not run on Debian for 
> x86_64. I tried 
> > the standard debian but that causes problems too.
> > Now i was wondering - is there a way for xen to imitate a 
> 32Bit System 
> > to the OS? I guess what would do the trick is if uname -m 
> would report 
> > an ix86 as the installer of the software that i need seems 
> to be using 
> > this...
> 
> All I know is that you can run a 32bit userland in a DomU 
> while the DomU Kernel is 64bit.
> 
> It runs very well on one of my 64bit Dom0s running a 64bit 
> DomU Kernel on a 32bit DomU userland with OpenGroupware.org 
> installed on it. But nevertheless "uname -m" says x86_64 then.

A para-virtualized Linux can not be run on a hypervisor with "different 
bitness" - so to you'll have to use 64-bit DomU if you use 64-Bit Xen - and of 
course, Dom0 has to be same as DomU, as they both use the same interface - just 
that Dom0 happens to be able to do some things that DomU can't do... 

If you run on a fully-virtualized platform, such as the AMD SVM (formerly 
Pacifica) or Intel VTx, you can run unmodified kernels, so you could run 16-bit 
DOS, 32-bit Linux or Windows, on a 64-bit Hypervisor. Dom0 still needs to be 
64-bit Para-virtualized. 

To get uname -m to report something else, you should be able to use setarch, 
see: 
http://linuxcommand.org/man_pages/setarch8.html

You may need to INSTALL setarch from someplace. Note that this affects the 
current application, but if you want, you can do something like "setarch i386 
bash", and thus start another shell with the architecture set to i386, where 
you could continue to install other software that needs to think that the 
system is 32-bit. MOST software, installers in particular, should really 
understand that x86_64 is a superset of ix86, but for older stuff that's not 
always the case. 

--
Mats
> 
> Greetings
> Robin
> 


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