HP-UX System Administrator's Guide: Overview

init init is both a daemon and a command.
The init command interacts with the init daemon. You use the init
command to set or change run levels.
The init daemon, started at boot time spawns processes as defined in the
/etc/inittab file. These processes in turn control how HP-UX interacts
with the outside world (for example, which terminals to accept input from,
and whether or not to export local file systems via NFS for use by other
servers).
NOTE: If your goal is to transition HP-UX to single-user mode from a
higher run level, do not use init s. This could leave processes running
and disks mounted that you do not want present.
Use the shutdown command with no parameters to transition to run level
s, or to be absolutely certain no undesirable processes or mounted file
systems are present, reboot the system to single-user mode by interrupting
the boot process and using the secondary boot loader (hpux.efi for
Integrity servers or hpux for HP 9000 servers) to override the default run
level.
who -r The -r option of the who command displays the current system run level,
the date and time the current run level was entered, and three state fields
representing the current run level, how many times that run level was
previously entered (since the system was booted), and the previous run
level (from which the current run level was entered).
Example:
who -r
. run-level 3 Jun 27 06:22 3 1 4
This output indicates:
• The system is currently in run level 3.
• It entered the current run level on June 27th at 22 minutes after six in
the morning.
• The current run level is (3) was previously entered one (1) time since
the system was last booted, and the current run level was entered from
the previous run level which was four (4).
Starting (Booting) HP-UX
HP-UX based systems go through the following sequential steps when you power them
on or reset them:
1. Hardware and/firmware-based routines on-board the processors and I/O cards
perform self-tests and initialize those items along with enough memory to continue
92 Major Components of HP-UX