Re: [Xen-users] How much is involved in porting a new OS to Xen fullvirtualizaiton?

[Nico Kadel-Garcia <nkadel@xxxxxxxxx>]

Nick Couchman wrote:
> Well, first, you're going to have a lot of trouble getting anyone to 
> touch SCO these days.  With all the legal stuff they've pulled over 
> the past couple of years I'm sure that no one is going to be eager to 
> get in their way on purpose.
>  
> What issues are you having getting SCO to run under XEN?  
> Theoretically, with XEN HVM support, you ought to be able to run just 
> about any O/S.  XEN HVMs emulate a standard set of hardware similar to 
> VMware, so you just need to figure out what the hardware is and make 
> sure the correct drivers are loaded.  I've run into some issues with 
> O/Ss on XEN HVMs, but mostly they're older O/Ss that don't support 
> idle calls to the CPU (like DOS with Symantec Ghost).  Let us know 
> what trouble you're having with OpenServer and maybe someone out there 
> has experience getting it to run on XEN.
>  
> If it doesn't run on XEN at all, making it work would probably involve 
> something like writing device drivers that support the XEN hardware.  
> Also, you can bet there will be a difference between the default 
> drivers included with the O/S and optimized drivers - similar to 
> VMware's Tools and the PV drivers for Windows under XEN.  Writing the 
> optimized ("PV") drivers is going to be the next step, and I'm afraid 
> I can't help you there and that you'll run into a lot of people who 
> don't want to touch SCO - either out of fear or out of disgust.
>  
> -Nick
It's appreciated: I'm on a contract to migrate SCO based software to 
RHEL, and there are plenty of legacy fiscal and medical systems that are 
running software which is needed for legacy data access, doesn't have 
source code for migration, or for which the owners lack the resources to 
do the software migration. So getting it running in a clean Xen-ified 
environment would be a showpiece for open source superiority, and ease 
the migration pain by providing an open source supported virtualization 
environment. I'd be thrilled to migrate the active services to Xenified 
virtual images, in order to free hardware for other uses and have 
managable OS images without the backup requirements of maintaining live 
systems or having to re-install the OS on future virtualization platforms.
The theory of everything working under HVM is good, but when I boot RHEL 
5.1 provided Xen with a scrubbed disk image, mounted as an IDE drive and 
using the installation CD, it gets to the installation scanning for 
hardware on the CD and fails to detect the drive. My suspicion, thinking 
about it, is that the virtualized IDE system uses a controller that 
isn't known to the SCO OpenServer installation tools. But for that, I 
need more extensive familiarity with Xen's hardware emulation and 
preferably intimate experience with SCO OpenServer's drivers.
There are some published notes on getting SCO OpenServer working with 
SCSI based virtual controllers that reveal the intricacies of driver 
management for that OS: it harkens back to the 1980's in its style and 
complexity, and the need for secret bits of command-line knowledge. 
Using IDE controllers just avoids that whole problem for VMware, but 
I've not gotten so far with Xen.
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