For instance, if you load a ramdisk image at a location in low When booting images that have been loaded to RAM (for instance using TFTP download) you have to beĬareful that the locations where the (compressed) images were stored do not overlap with the memory To boot a Linux kernel image without a initrd ramdisk image, the following command can be used:īoth examples imply that the variables used are set to correct addresses for a kernel and a initrd ramdisk image.
In this case the bootm command consists of three steps: first the Linux kernel image is uncompressed and copied into RAM, then the ramdisk image is loaded to RAM, and finally control is passed to the Linux kernel, passing information about the location and size of the ramdisk image. The U-Boot distribution has sources for these commands, named fwprintenv and fwsetenv. It can be helpful to read and set these variables from Linux as well. If it is present, it is interpreted as the start address of a initrd ramdisk image (in RAM, ROM or flash memory). U-Boot makes use of environment variables which can be read and set from the U-Boot command line with printenv and setenv. The first argument to bootm is the memory address (in RAM, ROM or flash memory) where the image is stored, followed by optional arguments that depend on the OS.įor Linux, exactly one optional argument can be passed. During the bootdelay countdown, you can interrupt. This U-Boot command 'ums' is infinite (a loop in USB treatments), and the U-Boot.
To create a U-Boot script image, commands are written to a text. The bootdelay variable defines a delay, in seconds, before running the autoboot command defined by bootcmd. In U-Boot, you can directly export the available block devices (sd/mmc/usb) as USB mass storage devices with ums command: help ums ums - Use the UMS USB Mass Storage Usage: ums0 Freescale Semiconductor 3 4 List of Commands 4.1 AUTOSCR Run script from memory: autoscr addr - run script starting at addr - A valid autoscr header must be present The autoscr command allows shell scripts to run under U-Boot. Depending on the OS it will pass the required boot arguments and start the OS at it's entry point. List of Commands U-Boot Quick Reference, Rev.
Note that this includes /etc/rc.local, so you will need to disable the watchdog timer as above first. Boots to a root console, disabling all but the absolutely essential boot sequence commands. The command will then load the image to the required memory address, uncompressing it on the fly if necessary. Boot the Edison into a rescue-mode console. From the image header it gets informationĪbout the type of the operating system, the file compression method used (if any), the load and entry point addresses, etc.
#U boot commands manual
The bootm command is used to start operating system images. iWave iW-RainboW-G21M Manual Online: u-boot testing and boot configuration, Basic Commands. ' when booting a Linux kernel,‘arg' can be the address of an initrd image Bootm ] - boot application image stored in memory passing arguments 'arg
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