Hi Back in June last year had the same issue, now on openSUSE 12.3 it's yet again failing building for me with the following command;

"env" "rootfstype=ext3" "mkinitrd" "-d" "/dev/null" "-m" "ext3 ext4 btrfs reiserfs binfmt_misc virtio_pci virtio_blk" "-k" "/boot/vmlinuz" "-i" "/boot/initrd-3.7.10-1.16-desktop-virtio"

Kernel image: /boot/vmlinuz Initrd image: /boot/initrd-3.7.10-1.16-desktop-virtio KMS drivers: i915 Could not find the filesystem type for root device /dev/null

Currently available -d parameters are: Block devices /dev/<device> NFS <server>:<path> URL <protocol>://<path> There was an error generating the initrd (1)

Yet on SLED 11 SP3 with uefi/secure boot (different machine HP 2000 AMD cpu and radeon) it works as expected?

This machine is a HP ProBook 4430s with qemu-kvm working to run up an iso image etc... I'm also running btrfs on both systems. Or could it be udev related?