板子刚启动，狂按回车键，即可修改环境变量
setenv ethact ‘ravb‘
setenv ethaddr ‘2E:09:0A:00:C1:13‘
setenv ipaddr ‘192.168.1.200‘
setenv serverip ‘192.168.1.4‘
setenv bootcmd ‘usb start; run usbload; booti 0x48080000 - 0x48000000‘
setenv bootargs ‘root=/dev/sda2 rw ip=192.168.1.200 video=HDMI-A-1:1280x800 video=HDMI-A-2:1280x800 rootdelay=3‘
setenv usbload ‘fatload usb 0 0x48080000 Image; fatload usb 0 0x48000000 r8a7795-salvator-xs.dtb‘
保存变量，及时生效
saveenv