iOS Components and Structure

Question 1

iOS Kernel

Answer 1

XNU Kernel

Question 2

iTunes or Over-the-Air

Answer 2

Updates to iOS can be accomplished either using iTunes installed on a computer with the device attached or via Over-the-Air (OTA) on the device itself. Updates can also be downloaded to a local network server running OS X Server so devices can be updated without connecting to a server.

Question 3

Boot ROM

Answer 3

When an iOS device is powered on, the application processor executes code from the boot ROM. Boot ROM code cannot be modified once created and is written onto the chip during fabrication. It is implicitly trusted and contains the Apple Root public key used to verify the Low-Level Bootloader (LLB) is signed by Apple before allowing it to load.