• Registered: 2015-12-06
  • Posts: 6

Topic: Boot from second SD card reader

I am experimenting with alternative boot images for my Novena laptop. After I write the image to a card inserted into the slot accessible from the side panel, I would like to boot it without having to swap out the microSD card in the reader that is installed directly on the board.

Ideally I would like a prompt to choose the SD card reader to boot from. How could this be done?

  • xobs
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  • Registered: 2014-05-25
  • Posts: 442

Re: Boot from second SD card reader

The source of the root filesystem is really just the PARTUUID parameter that gets passed to the kernel.  You can add a uEnv.txt script to choose the external SD slot.  We did something like this to your Novena when it was first imaged.

An example of how to create the script is available at https://github.com/xobs/novena-test#use … test-image

There is one other thing you need to do if you want to pull the kernel from the external SD slot.  This code from U-Boot will set "bootdev" depending on where U-Boot itself loaded from: https://github.com/xobs/u-boot-novena/c … a2c389R301

That means, if you want to load the KERNEL from the external SD slot, you ALSO need to add a uEnv.txt entry like:

setenv bootdev 1

You might be able to use extlinux to accomplish what you're trying to do.  I'm not entirely sure what it is, but it should be supported.

  • Registered: 2015-12-06
  • Posts: 6

Re: Boot from second SD card reader

Great, thanks!