Its not fully detailed boot process. Its very short form of things happens during boot. To make it understand and remember (for interviews) easily!
1) PDC (processor dependent code) gets executed
- Checks CPU
- Checks stable storage for boot path
- Loads ISL utilities from leaf area of boot disk
- Here you can halt boot using ESC key and can run PO, SEA commands.
2) ISL (Initial system loader) gets loaded
- Read AUTO file default kernel
- Load and runs HPUX from LIF area
- Here you can halt boot process and boot system into single user mode. U can provide diff options to SSL i.e. kernal vmunix. Like hpux –is, hpux –lq, hpux –lm
3) HPUX loads (Secondary system loader)
- Uses options and path names from ISL to load kernel
- And by default loads vmunix
4) After kernel vmunix gets loaded –
- Swapper daemon starts with PID 0
- Kernel runs /sbin/pre_init_rc
- Kernel calls /sbin/init
- /sbin/init reads /etc/inittab and calls –
- /sbin/ioinit – to scan hardware and build kernel io tree
- /sbin/bcheckrc – to check FS listed in /etc/fstab
- /sbin/rc – to start additional services like lp, cron, cde
- /usr/sbin/getty – to start n show login prompt to user.
Please note that this is not exact hpux boot process. There are alterations depends on system being referred is PA-RISC or Itanium. This article gives fair idea about whats happening in background when HPUX boot happens.