HP-UX Booting Process Overview.

System boot process:

-Power on
-PDC executes CPU, Memory and other tests
-PDC initialize the console to display messages
-Looks for Primary boot path
-It loads and executes Initial System Loader (ISL). Roll of boot ROM ends.
-ISL loads the secondary system loader called "hpux". It resides on boot area of the disk.
-"hpux" loads "/stand/vmunix" into memory and hands control over to kernel
-Kernel loads the device drivers
-Swapper process started. It has process ID 0. It manages memory for swapping in and out. It schedules all other process. Its first job is to startup the init process.
-/sbin/pre_init_rc getting executed. It checks and repairs root file system.
-/sbin/init started. Process ID is 1. It refers /etc/inittab. It does the following.

Read the /etc/inittab for default run level
-ioinitrc - It invokes insf command with -e option to find any new devices.
-bcheckrc - activates LVM and run fsck on file systems if required.
-/sbin/rc - It brings the system to the default run level. This script is run whenever the system moves from to a higher one or vice versa.
-/usr/bin/getty