I'm using u-boot to boot from various devices with modules disabled in the 2.6.24 kernel (everything compiled in). I boot directly from whatever device and don't use an initrd or initramfs.

When I was experimenting with booting from an SD Card the kernel panic message told me that the available partition was b301 so I used b301 as the root= in bootargs and it worked perfect (this was connected to SD slot, not on USB)

Now I'm trying to boot from an externel USB HD and I can't seem to figure out what root device to use. The boot messages say that it recognizes the USB HD on USB and that both USB mass storage support and SCSI emulation are working. When I boot to the SD card, udev sets the USB HD partitions to sda1 and sda2 and I can mount, r/w etc.

So I know the HD works, its just a matter of figuring out what device to use in root=

Any ideas or websites with hints or device name lists like the b301 for SD card?

ANd just in case its useful

s3c2410-ohci s3c2410-ohci: S3C24XX OHCI
s3c2410-ohci s3c2410-ohci: new USB bus registered, assigned bus number 1
s3c2410-ohci s3c2410-ohci: irq 42, io mem 0x49000000
usb usb1: configuration #1 chosen from 1 choice
hub 1-0:1.0: USB hub found
hub 1-0:1.0: 2 ports detected
usb usb1: Product: S3C24XX OHCI
usb usb1: Manufacturer: Linux 2.6.24.4 ohci_hcd
usb usb1: SerialNumber: s3c24xx
Initializing USB Mass Storage driver...
usb 1-1: new full speed USB device using s3c2410-ohci and address 2
usb 1-1: configuration #1 chosen from 1 choice
hub 1-1:1.0: USB hub found
hub 1-1:1.0: 4 ports detected
usb 1-1: Product: USB2.0 Hub
usb 1-1.1: new full speed USB device using s3c2410-ohci and address 3
usb 1-1.1: configuration #1 chosen from 1 choice
usb 1-1.1: Product: FireLite
usb 1-1.1: Manufacturer: SmartDisk
usb 1-1.1: SerialNumber: RD598SA0000000018158
usb 1-1.2: new low speed USB device using s3c2410-ohci and address 4
usb 1-1.2: configuration #1 chosen from 1 choice
usb 1-1.2: Product: USB Multimedia Keyboard
usb 1-1.2: Manufacturer: LITEON Technology
usb 1-1.3: new low speed USB device using s3c2410-ohci and address 5
usb 1-1.3: configuration #1 chosen from 1 choice
usb 1-1.3: Product: USB-PS/2 Optical Mouse
usb 1-1.3: Manufacturer: Logitech
scsi0 : SCSI emulation for USB Mass Storage devices
usbcore: registered new interface driver usb-storage
USB Mass Storage support registered.

I think its like /dev/sda or /dev/sdb, sdb0, etc., something like that. I think because the usb hard drive stuff goes through the scsi interface?

I tried those but they weren't recognized. However, after reading your email I tried was thinking about it and realized that I probably didn't have enough of a delay to allow the kernel to find the drive. It had been showing up during busybox init and I thought it was the busybox initialization that was setting the drives up as sdaX. In fact, that was the kernel doing it in the middle of the init process.

I changed my rootdelay= to 10 (it was 3) and the drive showed up as 0800 (sda), 0801 as sda1 (partition 1), 0802 as sda2 (partition 2), etc.

If sda1 doesn't work for root= then 0801 will.

Thanks for the prod!

Sure enough, sda1 isn't recognized but 0801 is.