[fedora-virt] First time xen install - Xen DomU runs, but can't find "/dev/root"

[M A Young]

On Wed, 16 Oct 2013, G Crowe wrote:

> I'm trying to get started with Xen and thought I'd do a simple install
> Fedora 18 as a DomU under a Fedora 18 Dom0. Unfortunately this is not
> working for me.
> 
> It appears to boot the kernel fine, but then complains that it can't find
> "/dev/root". I presume that this would be a specific root image for the
> Fedora installer?
> 
> The logs indicate that the kernel command line is empty. Apparently there
> should be something in there (maybe "root=/dev/xvda") but I am not sure how
> to achieve this. I would have expected virt-install to do this for me,
> though.
> 
> Can someone please let me know what I am doing wrong? (details of what I am
> trying are below).
> 
> Also, I had to manually start "xend" to get this far. Is this normal? It
> didn't appear in the services in /etc/rc.d/init.d

In xen, xend is gradually being phased out in favour of the libxl 
interface, and it isn't started by default on Fedora. If you want to 
enable it on boot run
systemd enable xend.service

> I created a 20GB logical volume /dev/fedora_dhcp1/xen1
> I mounted the Fedora 18 installation ISO into /mnt/install (-t iso9660 -o
> loop,ro)
> I created a bridge "brctl addbr br0" (I haven't added any interfaces to it
> yet, I plan to sort out the network after getting virtualisation working)
> I created the Xen DomU instance using the following command...
> [root at dhcp1 ~]# virt-install --paravirt --name xen1 --ram 256 --vcpus 1 -f
> /dev/fedora_dhcp1/xen1 --network bridge=br0 --location /mnt/install
> --graphics none

I am not an expert on using virt-install but I think you need to pass the 
install image to the guest as a disk as the --location option only fetches 
the kernel and initrd needed for the initial boot. You probably also need 
to add options to the boot line to tell the installer how to find the 
install image or stage2 file.

 	Michael Young