14.3.19. Combining a Kernel and a Ramdisk into a Multi-File Image

Question:

I used to build a zImage.initrd file which combined the Linux kernel with a ramdisk image. Can I do something similar with U-Boot?

Answer:

Yes, you can create "Multi-File Images" which contain several images, typically an OS (Linux) kernel image and one or more data images like RAMDisks. This construct is useful for instance when you want to boot over the network using BOOTP etc., where the boot server provides just a single image file, but you want to get for instance an OS kernel and a RAMDisk image.
The typical way to build such an image is:

bash$ mkimage -A ppc -O Linux -T multi -C gzip \
-n 'Linux Multiboot-Image' -e 0 -a 0 \
-d vmlinux.gz:ramdisk_image.gz pMulti

See also the usage message you get when you call "mkimage" without arguments.