Re: [Xen-users] Does XCP support network boot/diskless dom0?

[Pasi Kärkkäinen <pasik@xxxxxx>]

On Wed, Mar 10, 2010 at 10:39:33AM +0000, Alex Zeffertt wrote:
> Dave Scott wrote:
>>> either PXE or iSCSI.  I am investigating a move to XCP at our next
>>> hardware refresh and going diskless with the dom0s would nice.
>>
>> Not yet...
>>
>> I believe Alex [cc:d] has some early prototype code which enables this kind 
>> of thing. Alex, could you describe what it can do/ roughly how it works?
>>
>> Thanks,
>> Dave
>>
>
> Hi Dave/Matt,
>
> The diskless support that I have been working on is based on booting an 
> iSCSI disk.  Accesses to this disk is via a software initiator.
>
> Both dom0 and the host-installer need to be told what disk to access and 
> how to access it.  This is done via the iBFT (iSCSI Boot Firmware Table) 
> in low memory.  This table is either written by the BIOS (if the BIOS 
> supports boot from iSCSI), or by a boot ROM in a NIC (if there is a NIC 
> that supports boot from iSCSI), or even by a PXE network boot program 
> like gPXE.  However, NICs listed in the iBFT are reserved for root disk 
> access and cannot be used for management or by VMs.
>
> If you don't have a BIOS that supports boot-from-iSCSI it can be quite 
> tricky to set up a PXE server with the right configuration so that the 
> diskless servers download the correct gPXE binary which sets up the iBFT 
> correctly before running the host-installer or booting the iSCSI LUN.  
> For this reason, I've created an appliance VM which I'm calling the 
> XenBootServer.  This provides an ncurses UI for commissioning new 
> diskless XenServers and provides the PXE server, online install media, 
> and answerfiles for you.  All you have to do is answer a few simple 
> questions.
>

Nice project! is it available already from somewhere? 

Another question: Have you thought about making XCP totally stateless? 
ie. make XCP run from PXE-booted ramdisk root? And have all the 
state/configuration
on some management server/node..

This is how VirtualIron (using Xen) used to work..

-- Pasi


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