Re: [Xen-users] how can you boot an existing linux domU off the cdrom on sles11 dom0?

[James Pifer <jep@xxxxxxxxxxxxxxxx>]

> PV domUs don't really boot off of a device, per se.  PV domUs must first load 
> a kernel (and possibly initrd), then the software inside the domU deals with 
> finishing off the boot process.  In SLES, this happens using either 
> domUloader or pygrub to find and grab the kernel out of the domU disk and 
> pass the correct argument.  vm-install searches for a kernel file or kernel 
> package on the ISO or CD, and unpacks and/or loads that.
> 
> All that said, here's what I'd suggest:
> - Use virt-manager and/or vm-install to kick off an installation.
> - Specify your existing domU disk, and the SLES11 CD-ROM
> - Configure hardware as needed
> - On the final screen, where you choose the installation media, make sure to 
> specify the CD-ROM as the install source (it usually defaults to hard disk if 
> it finds something on it)
> - On that same screen is a place for extra arguments.  Add "rescue=1" as an 
> extra argument and boot.  This should take you into the rescue system for the 
> CD-ROM, and you can modify the files as needed.
> 
> Another alternative is to do the following:
> - Edit your VM config file and add the following for the extra= line: 
> "init=/bin/bash"
> - Reload the config file and boot.
> - The system should boot and take you directly to a bash prompt, where you 
> can remount the root device as R/W (mount -o remount,rw /) and then edit the 
> files.
> - Once you're done, remount as R/O, shut down (or destroy) the domain, and 
> undo the change to the config file.
> 
> -Nick
> 

Nick, 

Thanks for the response. Always appreciate your help. 

I don't think the first part will work because I need the scsi pci card
attached for the domU when it boots. So doing it as a new installation
won't work, unless I can somehow add that PCI device. 

The second part might work if I add the init=/bin/bash and also add
pci=['0e:04.0','0e:04.1'] to the config. Then xm create it. So it would
be:

xm delete domU
modify config file for extra parameter and pci line
xm create domU
hopefully get to a bash prompt and have enough info to do what is needed
xm destroy domU
xm delete domU
modify config again and remove "extra" parameter
xm create domU

That cover it?

Side note question. How come Citrix XenServer can do this so easily? I
tested XenServer a couple months again, and through their XenCenter
management package it was as easy as selecting a cd iso for the cdrom
device, and the domU would boot. Now that I think about it, maybe that
was only an Windows HVM domU. Maybe a linux PV would have the same
issue...

Thanks,
James


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