Description of files that are in image files folder in Yocto project and the boot sequence of Yocto linux

Question

Currently I'm working on a project using yocto. I want to know the purpose of following files

1. boot.bin
2. core-image-****-rootfs.cpio.gz.u-boot
3. u-boot-img
4. uEnv.txt
5. uImage
6. ****.dtb

and want to know the involvement these files when booting and the involevement order of them when booting the yocto Linux system.

Answer 1

Please understand that the following explanation is only valid for this specific question, and neither valid nor exhaustive for generic linux boot sequences.

1. boot.bin is usually some first stage loader, limited in size. Only enough to make the CPU capable of loading the real bootloader.
2. ´core-image-....´ is the generate root file system. The exact name and ending differ depending on the selected image target and IMAGE_FSTYPE in yocto
3. u-boot.img is the binary of the u-boot bootloader. This is being loaded by boot.bin.
4. uEnv.txt is the environment file of the u-boot bootloader. This can contain preset variables or scripts, for example.
5. uImage this is the linux kernel binary, package in the uImage format.
6. *.dtb is the devicetree file that tells the linux kernel about the details of the hardware in use. It depending on the specific board, it can also be used by u-boot.