Use following steps to use USB drive as root file system,

1) Press CTRL-C to stop any  Redboot script when power up the board

2) At Redboot command prompt, load kernel image
	a) from FLASH memory using following command,
		fis load zImage

	or load it from TFTP server using following command,
		load -r -v -b 0x80000 -h <TFTP server IP address> <kernel image file name>
	
3) Use the following command to boot system use USB drive as root file system
	a) 2.4.21 kernel with USB root file system patch
		exec -c "console=ttyAM0 root=/dev/sda1"

	b) 2.6.x kernel
		exec -c "console=ttyAM0 root=/dev/sda1 rootdelay=15"

Depending on the USB drive and system configuration, the delay time can be adjusted to 
obtain best result.


Note: All GESBC-93xx boards come with pre-build kernel that has USB storage option enbaled.  
If you build your own kernel please make sure the USB storage and SCSI are configured in 
order to use USB drive.