Re: [Xen-users] domU startup freezes at "Starting plymouth"

[Mike Wright <mike.wright@xxxxxxxxxxxxxx>]

On 07/02/2011 03:12 PM, Fajar A. Nugraha wrote:
> On Sun, Jul 3, 2011 at 2:25 AM, Mike Wright<mike.wright@xxxxxxxxxxxxxx>  wrote:
> > Hi all,
> >
> > I've got xen-4.1.1 running with linux-3.0.0-rc5 and am trying to start my
> > first guest, f14-x86_64, which does boot on bare metal.
> ... and here's the first mistake. I assume you're converting an
> existing linux installation to Xen?
> I highly suggest NOT to do so on your first domU/guest.
>
> > The configs below show kernel, ramdisk, and disk assignments for the virtual
> > machine.  They also show that the virtual machine uses the target disk
> > devices.  The last section shows part of the boot sequence starting with the
> > disk assignments, which are successful.  Everything stops at the last line
> > until some time later when the messages "Boot has failed, sleeping forever"
> > appears.  (I think this is about where the initramfs hands off control to
> > the kernel.)
> >
> > dom0: /etc/xen/vm1
> >
> > kernel = "/boot/vmlinuz-3.0.0-rc5"
> > ramdisk = "/boot/initramfs-3.0.0-rc5.img"
> This is the first mistake.
>
> While domU can use kernel located in dom0, if you choose to do so then
> you also need to specify the additional kernel arguments needed (e.g.
> "root=/dev/xvda1"). It should be on an "extra" line.
>
> Also, you need to have a matching set of modules in domU's
> /lib/modules (although this does not directly related to the error
> you're having now).
>
> > disk = [ 'phy:/dev/OneTB/f14_64,     sda1,w',
> >          'phy:/dev/OneTB/f14_64_swap,sda2,w' ]
> this one should be xvda instead of sda
>
> > [    0.171095] blkfront: xvde1: flush diskcache: enabled
> > [    0.172102] blkfront: xvde2: flush diskcache: enabled
> ... and you need to match "root=..." kernel arg to whatever's detected
> here. Since you use sda on the config file, F14's kernel will actually
> detect the disk as xvde, which can be confusing. Better stick with
> xvda.
>
> > If I can get just one vm running I'll be on my way...  I've been stuck here
> > since yesterday.  Any help appreciated.
> The best way for beginners is start with the easy things first.
> Install virt-manager, install a new domU, look at the generated config
> file and disk image, then start changing things from there.
Thanks for your help Fajar.

I think you may be being a bit alarmist ;)  All I was missing was the 
root = (or extra =) option (my fault for not reading all the way to the 
bottom) and that sda1 and sda2 have been superceded by xvda1 and xvda2.
Here are the basics from my vm1 config file:
(boots the virtual machine w/o networking)

kernel = "/boot/vmlinuz-3.0.0-rc5"
ramdisk = "/boot/initramfs-3.0.0-rc5.img"

# vif = ['']

disk = [ 'phy:/dev/OneTB/f14_64,      xvda1, w',
         'phy:/dev/OneTB/f14_64_swap, xvda2, w' ]

root = 'root=/dev/xvda1 ro'

Here are the required changes to the virtual to boot:

Mount the virtual's root partition and make these changes:

/mnt/etc/fstab
  /dev/xvda1 /     ext4 defaults 1 1
  /dev/xvda2 /swap swap defaults 0 0
  #comment out /boot

make sure /lib/modules has matching modules (in my case "3.0.0-rc5").

Now to figure out networking...

Thanx,
Mike Wright

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