U‑Boot is a boot loader program that is usually stored in flash memory on the embedded system. U‑Boot can load files from a variety of peripherals such as a serial connection, an ethernet network connection, or flash memories. Often times, U-Boot is the program that gets executed at system reset which will automatically load up another application (such as the Linux kernel). U-Boot can even parse many types of filesystems on many types of storage devices.
READMEfile in the U-Boot source code.
The following is an incomplete list of available commands that can be executed from the U‑Boot command line. The supported commands may differ according to your configuration and version. Please refer to compiling. This list can be displayed within U‑Boot by executing the help command.
bfin> help ? - alias for 'help' autoscr - run script from memory 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' bootelf - Boot from an ELF image in memory bootldr - boot ldr image from memory bootm - boot application image from memory bootp - boot image via network using BOOTP/TFTP protocol bootvx - Boot vxWorks from an ELF image cmp - memory compare coninfo - print console devices and information cp - memory copy cplbinfo- display current CPLB tables crc32 - checksum calculation date - get/set/reset date & time dcache - enable or disable data cache dhcp - boot image via network using DHCP/TFTP protocol echo - echo args to console eeprom - EEPROM sub-system erase - erase FLASH memory flinfo - print FLASH memory information fsinfo - print information about filesystems fsload - load binary file from a filesystem image go - start application at address 'addr' help - print online help icache - enable or disable instruction cache icrc32 - checksum calculation iloop - infinite loop on address range imd - i2c memory display iminfo - print header information for application image imls - list all images found in flash imm - i2c memory modify (auto-incrementing) imw - memory write (fill) imxtract- extract a part of a multi-image inm - memory modify (constant address) iprobe - probe to discover valid I2C chip addresses itest - return true/false on integer compare loadb - load binary file over serial line (kermit mode) loads - load S-Record file over serial line loady - load binary file over serial line (ymodem mode) loop - infinite loop on address range ls - list files in a directory (default /) md - memory display mii - MII utility commands mm - memory modify (auto-incrementing) mtest - simple RAM test mw - memory write (fill) 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 protect - enable or disable FLASH write protection rarpboot- boot image via network using RARP/TFTP protocol reginfo - print register information reset - Perform RESET of the CPU run - run commands in an environment variable saveenv - save environment variables to persistent storage setenv - set environment variables sleep - delay execution for some time strings - display strings tftpboot- boot image via network using TFTP protocol version - print monitor version