[Users] Pxeboot

[Mike Burns]

On Wed, 2012-02-08 at 15:19 -0800, Li, David wrote:
> Perry,
> 
> I am glad you brought this up.
> I 'd be perfectly happy to run the root fs entirely in RAM. In fact that would be ideal for me. It's just I am not quite sure how to use pxeboot to achieve this. 
> 
> I am doing a test now using the tftpboot files created from the iso. 
> As far as I see, the kernel boot options (pxelinux.cfg/default) has:
> 
> root=live:/ovirt-node-image-2.2.2-1.1.fc16.iso
> 
> With this I can only pxeboot to the intall screen.  What should I use to let the kernel mount the root fs in memory? Something like root=/dev/ram0?
> 
> David

It's not currently possible with ovirt-node.  That's the whole stateless
feature that we outlined.  Once we actually have it implemented, it will
be something along the lines of adding "stateless" to the kernel
commandline.  

Mike
> 
> 
> >-----Original Message-----
> >From: Perry Myers [mailto:pmyers at redhat.com]
> >Sent: Wednesday, February 08, 2012 2:54 PM
> >To: Mike Burns
> >Cc: Li, David; users at ovirt.org
> >Subject: Re: [Users] Pxeboot
> >
> >On 02/08/2012 05:03 PM, Mike Burns wrote:
> >> On Wed, 2012-02-08 at 13:46 -0800, Li, David wrote:
> >>> Mike,
> >>>
> >>> If I understand this correctly, today I should be able to pxeboot and
> >>> nfs mount the root fs from a remote server.  Apart from setting up
> >>> the pxe stuff, I 'd have to populate the ovirt node root fs on the
> >>> server
> >>> - perhaps steal it from a disk install.  In other words I am
> >>> concerned about the point from which the kernel starts to execute
> >>> /init script (in the initramfs) to the point /init is able to mount
> >>> the final root fs from a remote server.
> >>
> >> No, there is no way to set this up currently in ovirt-node.  You could
> >> install using a remote iscsi lun if you have a hardware iscsi HBA, but
> >> there isn't a way to mount a remote nfs share as the root fs.
> >>
> >> Supporting a remote NFS share as the root fs isn't even something that
> >> requested as an RFE at this point or on the roadmap as far as I'm
> >> aware.
> >>
> >> It sounds like what you're really looking for is a shared root fs that
> >> multiple hosts could use.  This is something that we will probably
> >> look into eventually, but it's not on the immediate roadmap.
> >
> >Given that the rootfs of oVirt Node is fairly small and in a truly stateless
> >environment would just run out of system RAM, there's no real reason to try
> >to do a shared NFS based rootfs.  It's an unnecessary complication I think, if
> >the end goal is to move to truly stateless.
> >
> >For larger systems where the rootfs is on the order of GB's, shared root may
> >make more sense.
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