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

[Alex Zeffertt <alex.zeffertt@xxxxxxxxxxxxx>]

Thiago,

There is currently support in XCP for diskless booting from an iSCSI root disk, 
although it was only recently added and don't know if has been built yet.
To install to/boot from an iSCSI LUN you need a BIOS or boot ROM that supports 
iBFT.  (This is a low memory table that allows the BIOS or boot ROM to 
communicate the settings to the OS.)  Alternatively you can use a PXE server 
with gPXE as this can also create an iBFT.
To install, the BIOS or boot ROM must set up the iBFT - but not boot it - so 
that the iBFT is available to the host installer.
At install time you need to start the host-installer in debug mode and append 
--use_ibft to the host installer command line.  After that everything should be 
straight forward.
At boot time the BIOS or boot ROM will setup the iBFT, load the boot loader off 
the LUN and then pass control to it.  After the kernel has booted it uses the 
iBFT to find the LUN, and attaches to the LUN using open-iscsi.
To simplify the process of setting up a PXE server we have created a XenServer 
appliance called xenbootserver.xva.  This probably isn't available yet but the 
code is there and it could be released as part of the next build.
This appliance provides the install media and also an ncurses wizard for 
creating per-host PXE and answerfile configurations.  It serves a modified 
version of gPXE that can specify a redundant path in the iBFT so that multipath 
booting is supported.  It also has iscsitarget installed (but not enabled) so 
that you can use the appliance as the iSCSI target too (if you really want to!)
To use the appliance simply import and follow the instructions in the appliance 
console.
Regards,

Alex Zeffertt



Martinx - ããããã wrote:
> Hi!
>
>  I think if we do a XCP Live CD, just like the Xen Live CD v2.0, the 
> same root file system of the XCP live session can be used to make XCP 
> run from PXE-booted ramdisk root. Since it will be a live system, the 
> entire system will naturally have its root rw fs at the RAM...
>  In fact, I'm planning to add a PXE server into the Xen Live CD, so when 
> you boot the Xen Live CD in your network, it will automatically provide 
> a network of diskless Xen servers using the same root file system of the 
> live CD itself, for the Xen diskless dom0s...
>  About the state files thats need to survive across XCP reboots can live 
> in another place... Maybe creating a dedicated shared storage for this 
> data will solve the problem...
> Any thoughts?!
>
> PS.: Sorry, my english is terrible, I know!  ^_^
>
> -
>  Thiago
>
> On 1 April 2010 06:40, Dave Scott <Dave.Scott@xxxxxxxxxxxxx 
> <mailto:Dave.Scott@xxxxxxxxxxxxx>> wrote:
>
>      > Nice project! is it available already from somewhere?
>
>     I think the necessary host-installer and filesystem changes will end
>     up in the next XCP snapshot build -- is that right, Alex?
>
>      > 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..
>
>     That's certainly an interesting idea. One of the problems we have
>     atm is that we don't have a good list of all the files in dom0 which
>     contain bits of state.
>
>     Cheers,
>     Dave
>
>
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