[Fedora-xen] Booting rootfs instead of disk image, question on xen modules

[Paul Wouters]

hi,

I am trying to boot using a rootfs image, instead of a disk image. Just because it
is much easier to mount filesystems, then to go calculate offsets for mounting. Also,
because I have various xen2 filesystems I want to use without building virtual disk
images. On FC5, using kernel= with a *xenU image works fine. On FC6, using the *xen
kernel image, this does not work. (using known working fc5 xen kernels on fc6 also
didn't work, but I expected that, due to differences in the xen hypervisor)

Instead of using bootloader="/usr/bin/pygrub" I manaully set the kernel, ramdisk
and extra flags, eg:

disk = [ 'file:/xen/qtopia.xelerance.net/qtopia.ext3.img,xvda1,w' ]
kernel="/boot/vmlinuz-2.6.18-1.2798.fc6xen"
root="/dev/xvda1 ro"
extra="ro selinux=0 3 root=/dev/xvda1 initrd=/boot/initrd-2.6.18-1.2798.fc6xen.img"
ramdisk="/boot/initrd-2.6.18-1.2798.fc6xen.img"
(also tried using hda1 instead of xvda1)

But when I boot, I see the following:

[...]
XENBUS: Device with no driver: device/vbd/51713
XENBUS: Device with no driver: device/vif/0
Freeing unused kernel memory: 180k freed
Write protecting the kernel read-only data: 356k
Red Hat nash version 5.1.19 starting
Mounting proc filesystem
Mounting sysfs filesystem
Creating /dev
Creating initial device nodes
Setting up hotplug.
Creating block device nodes.
Loading uhci-hcd.ko module
USB Universal Host Controller Interface driver v3.0
Loading ohci-hcd.ko module
Loading ehci-hcd.ko module
Loading jbd.ko module
Loading ext3.ko module
Loading scsi_mod.ko module
SCSI subsystem initialized
Loading sd_mod.ko module
Loading libata.ko module
Loading ahci.ko module
Loading ata_piix.ko module
Creating root device.
Mounting root filesystem.
mount: could not find filesystem '/dev/root'
Setting up other filesystems.
Setting up new root fs
setuproot: moving /dev failed: No such file or directory
no fstab.sys, mounting internal defaults
setuproot: error mounting /proc: No such file or directory
setuproot: error mounting /sys: No such file or directory
Switching to new root and running init.
unmounting old /dev
unmounting old /proc
unmounting old /sys
switchroot: mount failed: No such file or directory
Kernel panic - not syncing: Attempted to kill init!

It seems the xenblck and xennet drivers are not being loaded? And indeed,
dissecting the initrd file, I don't see them. However, grepping the config
shows they are now inline:

# grep XENB /boot/config-2.6.18-1.2798.fc6xen
CONFIG_XEN_XENBUS_DEV=y

So I am not sure why xen is not picking up the settings - though pygrub
can find them.

The same machine boots fine with pygrub, so it must be something that
I'm doing wrong myself. but even running xm create -n configname did
not give me a clue on what it is that I'm doing wrong.

I've attached the output of xm create -n below.

Using config file "/etc/xen/qtopia.xelerance.net".
(vm
    (name qtopia.xelerance.net)
    (memory 256)
    (on_reboot restart)
    (on_crash restart)
    (vcpus 1)
    (uuid 10000007-f66d-374b-29fc-364cd7761111)
    (image
        (linux
            (kernel /boot/vmlinuz-2.6.18-1.2798.fc6xen)
            (ramdisk /boot/initrd-2.6.18-1.2798.fc6xen.img)
            (root '/dev/xvda1 ro')
            (args
                'ro selinux=0 3 root=/dev/xvda1 initrd=/boot/initrd-2.6.18-1.2798.fc6xen.img'
            )
            (vncunused 1)
            (xauthority /root/.Xauthority)
        )
    )
    (device
        (vbd
            (uname file:/xen/qtopia.xelerance.net/qtopia.ext3.img)
            (dev xvda1)
            (mode w)
        )
    )
    (device (vif (bridge xenbr0) (mac 00:16:3e:7a:0e:57)))
)

Paul