5.9.3. Flash Memory Commands 1. Abstract 5.9.5. Download Commands
Prev Home Next

5.9.4. Execution Control Commands autoscr - run script from memory

INCA-IP # help autoscr
autoscr [addr] - run script starting at addr - A valid autoscr header must be present


With autoscr command you can run "shell" scripts under U-Boot: You create a U-Boot script image by simply writing the commands you want to run into a text file; then you will have to use the mkimage tool to convert this text file into a U-Boot image (using the image type script).

This image can be loaded like any other image file, and with autoscr you can run the commands in such an image. For instance, the following text file:

bash$ cat /tftpboot/INCA/example.script
echo Network Configuration:
echo ----------------------
echo Target:
printenv ipaddr hostname
echo Server:
printenv serverip rootpath

can be converted into a U-Boot script image using the mkimage command like this:

bash$ mkimage -A mips -O linux -T script -C none -a 0 -e 0 \
> -n "autoscr example script" \
> -d /tftpboot/INCA/example.script /tftpboot/INCA/example.img
Image Name:   autoscr example script
Created:      Wed Jul 30 02:41:47 2003
Image Type:   MIPS Linux Script (uncompressed)
Data Size:    157 Bytes = 0.15 kB = 0.00 MB
Load Address: 0x00000000
Entry Point:  0x00000000
   Image 0:      149 Bytes =    0 kB = 0 MB

Now you can load and execute this script image in U-Boot:

INCA-IP # tftp 100000 /tftpboot/INCA/example.img
TFTP from server; our IP address is
Filename '/tftpboot/INCA/example.img'.
Load address: 0x100000
Loading: *#
Bytes transferred = 221 (dd hex)
INCA-IP # autoscr 100000
## Executing script at 00100000

Network Configuration:


INCA-IP # bootm - boot application image from memory

INCA-IP # help bootm
bootm [addr [arg ...]]
    - boot application image stored in memory
        passing arguments 'arg ...'; when booting a Linux kernel,
        'arg' can be the address of an initrd image


The bootm is used to start operating system images. From the image header it gets information about the type of the operating system, the file compression method used (if any), the load and entry point addresses, etc. The command will then load the image to the required memory address, uncompressing it on the fly if necessary. Depending on the OS it will pass the required boot arguments and start the OS at it's entry point.

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.

For Linux, exactly one optional argument can be passed. If it is present, it is interpreted as the start address of a initrd ramdisk image (in RAM, ROM or flash memory). 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 controll is passed to the Linux kernel, passing information about the location and size of the ramdisk image.

To boot a Linux kernel image without a initrd ramdisk image, the following command can be used:

INCA-IP # bootm $(kernel_addr)

If a ramdisk image shall be used, you can type:

INCA-IP # bootm $(kernel_addr) $(ramdisk_addr)

Both examples of course imply that the variables used are set to correct addresses for a kernel and a initrd ramdisk image.

ALERT! When booting images that have been loaded to RAM (for instance using TFTP download) you have to be careful that the locations where the (compressed) images were stored do not overlap with the memory needed to load the uncompressed kernel. For instance, if you load a ramdisk image at a location in low memory, it may be overwritten when the Linux kernel gets loaded. This will cause undefined system crashes. go - start application at address 'addr'

INCA-IP # help go
go addr [arg ...]
    - start application at address 'addr'
      passing 'arg' as arguments


U-Boot has support for so-called standalone applications. These are programs that do not require the complex environment of an operating system to run. Instead they can be loaded and executed by U-Boot directly, utilizing U-Boot's service functions like console I/O or malloc() and free().

This can be used to dynamically load and run special extensions to U-Boot like special hardware test routines or bootstrap code to load an OS image from some filesystem.

The go is used to start such standalone applications. The optional arguments are passed to the application without modification. For more informatoin see 5.12. U-Boot Standalone Applications.

5.9.3. Flash Memory Commands 1. Abstract 5.9.5. Download Commands
Prev Home Next