The boot process

The boot process on a Zynq-based PandA proceeds through five stages:

1. Stage-0 boot loader (hard-wired in Zynq) Reads boot.bin from the SD card into memory and passes control to the stage-1 loader.

2. Stage-1 boot loader (inside boot.bin) Loads U-Boot from boot.bin.

3. Stage-2 boot loader: U-Boot Runs the boot script (boot.scr) which locates the FIT image (image.ub), checks its integrity, and boots the Linux kernel.

4. Kernel initialisation The kernel initialises hardware resources and then unpacks the initramfs image contained inside the FIT image. The init script within the initramfs is executed.

5. Initramfs init script Checks the configuration (including network settings from config.txt), prompts for a MAC address if one has not been set, and mounts the main rootfs image (rootfs.squashfs).

6. Rootfs init system The target system starts by running the init system inside the mounted rootfs image. PandA services (TCP server, web interface) are started here.

Key files on the SD card¶