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5.10. U-Boot Environment Variables

The U-Boot environment is a block of memory that is kept on persistent storage and copied to RAM when U-Boot starts. It is used to store environment variables which can be used to configure the system. The environment is protected by a CRC32 checksum.

This section lists the most important environment variables, some of which have a special meaning to U-Boot. You can use these variables to configure the behaviour of U-Boot to your liking.

=> setenv initrd_high 00c00000
     
Setting initrd_high to the highest possible address in your system (0xFFFFFFFF) prevents U-Boot from copying the image to RAM at all. This allows for faster boot times, but requires a Linux kernel with zero-copy ramdisk support.

=> setenv bootargs ${bootargs} mem=\${mem}
=> saveenv
     
This way you can tell Linux not to use this memory, either, which results in a memory region that will not be affected by reboots.

The following environment variables may be used and automatically updated by the network boot commands (bootp, dhcp, or tftp), depending the information provided by your boot server:

5.9.10. Miscellaneous Commands 1. Abstract 5.11. U-Boot Scripting Capabilities
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