系统启动后，进入到
U-Boot>
后输入help，将显示所有支持的内置命令，如下所示
? - alias for 'help'
base - print or set address offset
bdinfo - print Board Info structure
boot - boot default, i.e., run 'bootcmd'
bootd - boot default, i.e., run 'bootcmd'
bootm - boot application image from memory
bootp - boot image via network using BOOTP/TFTP protocol
bootz - boot Linux zImage image from memory
chpart - change active partition
cmp - memory compare
coninfo - print console devices and information
cp - memory copy
crc32 - checksum calculation
dfu - Device Firmware Upgrade
dhcp - boot image via network using DHCP/TFTP protocol
echo - echo args to console
editenv - edit environment variable
env - environment handling commands
exit - exit script
ext4load- load binary file from a Ext4 filesystem
ext4ls - list files in a directory (default /)
ext4write- create a file in the root directory
false - do nothing, unsuccessfully
fatinfo - print information about filesystem
fatload - load binary file from a dos filesystem
fatls - list files in a directory (default /)
fatwrite- write file into a dos filesystem
fdt - flattened device tree utility commands
go - start application at address 'addr'
help - print command description/usage
imxtract- extract a part of a multi-image
itest - return true/false on integer compare
loadb - load binary file over serial line (kermit mode)
loady - load binary file over serial line (ymodem mode)
loop - infinite loop on address range
md - memory display
mdio - MDIO utility commands
mii - MII utility commands
mm - memory modify (auto-incrementing address)
mmc - MMC sub system
mmcinfo - display MMC info
mtdparts- define flash/nand partitions
mtest - simple RAM read/write test
mw - memory write (fill)
nand - NAND sub-system
nboot - boot from NAND device
nfs - boot image via network using NFS protocol
nm - memory modify (constant address)
ping - send ICMP ECHO_REQUEST to network host
printenv- print environment variables
reset - Perform RESET of the CPU
run - run commands in an environment variable
saveenv - save environment variables to persistent storage
setenv - set environment variables
sf - SPI flash sub-system
showvar - print local hushshell variables
sleep - delay execution for some time
source - run script from memory
test - minimal test like /bin/sh
tftpboot- boot image via network using TFTP protocol
true - do nothing, successfully
ubi - ubi commands
ubifsload- load file from an UBIFS filesystem
ubifsls - list files in a directory
ubifsmount- mount UBIFS volume
ubifsumount- unmount UBIFS volume
usb - USB sub-system
usbboot - boot from USB device
version - print monitor, compiler and linker version