On 2016-12-22, Robert Latest wrote: > Given a bootable SD card, how can I change u-boot's behavior to, for > example, load a different kernel image or use different environment > variables (I'm most desperate to set the device to have a fixed MAC > address)?
It's entirely platform-dependent. Some platforms have it located at a raw offset on the boot media, some load a uenv.txt file, some load a uboot.env file, etc... You can configure flash-kernel to generate a boot script which can set variables in u-boot, if you platform supports loading a boot.scr. > I think the environment variables need to be written to a specific > location on the SD card, but u-boot-tools provides no such tool. man > fw_setenv needs a file /etc/env.config, but my system (which is a > finished image I copied from somewhere) doesn't have that. The locations are board-specific. There are some examples for /etc/fw_env.config in /usr/share/doc/u-boot-tools/examples/. I'd still suggest using a flash-kernel boot script instead, if you can, as saving the environment variables means when you upgrade u-boot, you don't benefit from new defaults if there are bugs fixed or improved features in the default environment. > - What's the difference between uImage and zImage, and why does one > kernel version have a uImage and the other a zImage? uImage is a wrapper that includes some checksums to verify image integrity. Many modern u-boot versions support loading the zImage file directly with "bootz". > - Is the "dts" file the source that the "dtb" file was created from, > or does it have some other purpose? Hopefully the dts is the source... although you can generate the .dts From the .dtb and compare to make sure... Sounds like the image you're using is using vendor-built kernels and presumably kernel trees, so the behavior of those may not be consistant with a debian-provided kernel image. live well, vagrant
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