Booting process about gadget

[colinliao]

Hi all,

I am new for ubuntu core, and I am trying to understand Ubuntu core.

I have confusion about gadget. base my understanding, gadget is snap file, and it can load and start kernel snap.

but if gadget is the first stage during booting, Who is responsible for extract gadget and get original uboot for starting? Because CPU can work with original uboot ( build from uboot source code by make ), but can’t work with gadget (not original uboot, it is a snap file builted by snapcraft).

[ogra]

Take a look at:

Building u-boot gadget snaps (a series of blog posts)

I just started a little series of HOWTO blog posts around gadget snaps, how to create them and how to build u-boot from source at https://ograblog.wordpress.com/2017/05/30/building-u-boot-gadget-snap-packages-from-source/ It uses the new https://github.com/ogra1/beaglebone-gadget as example code.

[colinliao]

Hi orga,

Thanks for your reply.

I already read the posts in your blog, take beaglebone gadge for example, snapcraft will generate a gadget snap base on MLO and uboot.img. I can understand the orignal booting process of beaglebone that CPU will start with MLO and then MLO will load uboot.img.

but if we start with gadget snap, CPU need to extract out MLO and uboot.img from gadget snap firstly. Who will do this?

thanks!

[ogra]

the files are put in place by the ubuntu-image command when it creates the img file … depeding what you have put into your gadget.yaml it will then write the created binary files to the right places…