Once the kernel and all drivers necessary for booting are loaded, the boot loader starts the kernel’s initialization procedure. On x86 macOS, iBoot is located in /System/Library/CoreServices/boot.efi. If the LLB or iBoot fails to load iOS, or fails to verify iOS, the bootloader jumps to DFU ( Device Firmware Update) mode otherwise it loads the remaining kernel modules. If all goes well, iBoot will then proceed to load the iOS kernel as well as the rest of the operating system. In systems with newer processors, the Boot ROM loads iBoot itself. In systems with S1 processors or A9 or earlier A-series processors, the Boot ROM loads the Low-Level Bootloader (LLB), which loads iBoot. įor iOS, the boot process starts by running the device's Boot ROM code. For ARM macOS, the Boot ROM is not UEFI component. Boot ROM has two primary responsibilities: to initialize system hardware and to select an operating system to run (the POST and UEFI component). įor x86 macOS, the boot process starts by running code stored in secured UEFI Boot ROM (first stage). Compared with its predecessor, iBoot improves authentication performed in the boot chain. IBoot is the stage 2 bootloader for all Apple products.
