To update the bootcmd variable to download the image on each boot, simply replace the command used to load the image from flash with the TFTP download command. For example, after loading the kernel image above, running bootm 0x70000000 would boot the board using the new image without making any changes to the images stored on the flash.
Furthermore, the boot command can be set such that the image is automatically downloaded and executed on each boot, making testing more efficient.Īfter loading a bootable image to RAM, you can execute it directly using the bootm command for a uImage kernel or bootz for a zImage kernel. This is especially helpful when testing new Linux kernel images. In some situations, it is advantageous to execute the image directly from RAM after loading with TFTP rather than saving to flash. Note that the filesize variable has been automatically updated to the size of the file that was loaded. The example below shows the use of DHCP and setting the TFTP server IP address to 192.168.2.1 Before continuing, determine a valid static network address for your local network contact your IT department for more information on what address to use if required. The network mask and broadcast address will be determined automatically from these settings, and no default gateway setting is required if the server is on the same subnetwork as the board. Typically, the IP address of the board and the IP address of the TFTP server are the only settings that need to be defined. Static networking configuration or DHCP can be used on some systems (requires DHCP server). In order to load a file using TFTP, U-Boot must be configured to access the local network. Please contact EMAC if you need details on how to use NFS instead of TFTP to load images. Information on how to set up an NFS server can be found here.
Alternatively, NFS can be used in place of TFTP but will require an NFS server. The specific details of TFTP server setup and configuration can be found on the Installing TFTP server page. A TFTP server must be accessible on the local network.
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