This is a demo implementation of a Linux command line tool to access the U-Boot's environment variables. In order to cross-compile fw_printenv, run make CROSS_COMPILE= envtools in the root directory of the U-Boot distribution. For example, make CROSS_COMPILE=arm-linux- envtools You should then create a symlink from fw_setenv to fw_printenv. They use the same program and its function depends on its basename. For the run-time utility configuration uncomment the line #define CONFIG_FILE "/etc/fw_env.config" in fw_env.h. For building against older versions of the MTD headers (meaning before v2.6.8-rc1) it is required to pass the argument "MTD_VERSION=old" to make. See comments in the fw_env.config file for definitions for the particular board. Configuration can also be done via #defines in the fw_env.h file. The following lines are relevant: #define HAVE_REDUND /* For systems with 2 env sectors */ #define DEVICE1_NAME "/dev/mtd1" #define DEVICE2_NAME "/dev/mtd2" #define DEVICE1_OFFSET 0x0000 #define ENV1_SIZE 0x4000 #define DEVICE1_ESIZE 0x4000 #define DEVICE1_ENVSECTORS 2 #define DEVICE2_OFFSET 0x0000 #define ENV2_SIZE 0x4000 #define DEVICE2_ESIZE 0x4000 #define DEVICE2_ENVSECTORS 2 Un-define HAVE_REDUND, if you want to use the utilities on a system that does not have support for redundant environment enabled. If HAVE_REDUND is undefined, DEVICE2_NAME is ignored, as is ENV2_SIZE and DEVICE2_ESIZE. The DEVICEx_NAME constants define which MTD character devices are to be used to access the environment. The DEVICEx_OFFSET constants define the environment offset within the MTD character device. ENVx_SIZE defines the size in bytes taken by the environment, which may be less then flash sector size, if the environment takes less then 1 sector. DEVICEx_ESIZE defines the size of the first sector in the flash partition where the environment resides. DEVICEx_ENVSECTORS defines the number of sectors that may be used for this environment instance. On NAND this is used to limit the range within which bad blocks are skipped, on NOR it is not used. If DEVICEx_ESIZE and DEVICEx_ENVSECTORS are both zero, then a runtime detection is attempted for NOR and NAND mtd types. To prevent losing changes to the environment and to prevent confusing the MTD drivers, a lock file at /run/fw_printenv.lock is used to serialize access to the environment.