setenv x_bootargs                'console=ttyS0,115200 panic=10 rootwait rootdelay=10'
setenv image_address             0x6400000

setenv bootcmd                   'run init; run bootcmd_sdb; run bootcmd_sda;'
setenv init                      'run clear_kernel_in_mem; run x_bootcmd_usb;'
setenv bootcmd_sdb               'setenv root_device /dev/sdb2; setenv usb_device_id 1; run boot_common;'
setenv bootcmd_sda               'setenv root_device /dev/sda2; setenv usb_device_id 0; run boot_common;'

setenv boot_common               'run bootcmd_echo_boot_attempt; run setargs; run x_bootcmd_kernel; bootm ${image_address};'

setenv clear_kernel_in_mem       'echo Purging kernel in memory; mw ${image_address} 0x0 0x300000;'
setenv bootcmd_echo_boot_attempt 'echo attempting to boot from: ${root_device};'
setenv setargs                   'setenv bootargs ${x_bootargs} root=${root_device}; echo bootargs="${bootargs}";'
setenv x_bootcmd_kernel          'fatload usb ${usb_device_id} ${image_address} uimage;'

saveenv