I have karmic on a USB drive, and I can boot the 2.6.31-5-generic kernel. But the 2.6.31-7-generic and the mainline 2.6.31rc7 kernel can not find the root device. dmesg only shows:
[ 1200.104015] usb 1-8: new high speed USB device using ehci_hcd and address 3
[ 1200.237017] usb 1-8: configuration #1 chosen from 1 choice
and cat /sys/bus/usb/devices/1-8/product gives "USB2.0 Storage Device" but I do not get the
[ 1200.278612] scsi7 : SCSI emulation for USB Mass Storage devices
[ 1200.278930] usb-storage: device found at 3
[ 1200.278934] usb-storage: waiting for device to settle before scanning
messages I get with working kernels. /proc/modules show only 17 modules, but usb-storage is loaded, and it is the same modules in 2.6.31-5.
I have LVM installed (but root is not on the LVM) so I initially thought it was bug 418514.
DistroRelease: Ubuntu 9.04
Package: linux-image-2.6.31-6-generic 2.6.31-6.25
ProcCmdLine: root=/dev/mapper/isw_ececbiichd_osmoraid6 ro quiet splash
ProcVersionSignature: Ubuntu 2.6.31-6.25-generic
UnreportableReason: This is not a genuine Ubuntu package