Tag Archives: ISL

HPUX boot process

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HPUX boot process explained. Learn which all processes happened in the background while HPUX server boots.

It’s not a fully detailed boot process. It’s a 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 the boot path
  • Loads ISL utilities from leaf area of the 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 the boot process and boot system into single-user mode. You can provide diff options to SSL i.e. kernel vmunix. Like,hpux –ishpux –lq, hpux –lm

3) HPUX loads (Secondary system loader)

  • Uses options and path names from ISL to load the 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 –
  1. /sbin/ioinit – to scan hardware and build kernel io tree
  2. /sbin/bcheckrc – to check FS listed in /etc/fstab
  3. /sbin/rc – to start additional services like lp, cron, cde
  4. /usr/sbin/getty – to start n show login prompt to the user.

Please note that this is not the exact hpux boot process. There are alterations depends on the system being referred to is PA-RISC or Itanium. This article gives a fair idea of what’s happening in the background when HPUX boot happens.