QNX BACKGROUND INFORMATION
I-E96-107-2N
D - 1
APPENDIX D - QNX BACKGROUND INFORMATION
QNX BACKGROUND INFORMATION
It is a good idea to familiarize yourself with the basic philoso-
phy and operation of QNX
™
as described in
QNX4 System
Architecture
and
QNX4 User’s Guide
(Section 1). This
appendix will provide a brief technical overview of QNX.
NOTE: In a standard installation of OIS12 software, there will be no
need to modify any of the files described in this section. This infor-
mation is intended to provide technical background information only.
THE SYSTEM INITIALIZATION FILE
What Happens When You Boot
When you boot QNX, you are booting an image composed of
several processes. The first process in the image is always the
Process Manager (which contains the Microkernel). The Pro-
cess Manager performs processor initialization, and then
schedules each process included within the image for execu-
tion. The last process in the image is the “sinit” utility.
The “sinit” utility initiates the second phase of your system ini-
tialization by starting a shell that executes commands from a
file. This file (the system initialization file) contains commands
that set up services for the machine. It is a standard shell file
that runs just like any other shell file except that breaks are
disabled.
Being able to start system services after boot is one of the ben-
efits of QNX’s modular architecture. The image that is booted
typically contains only those few essential services needed to
start all other desired services.
When “sinit” runs, it first determines if the image it is part of
was booted from disk or from over the network. If the image
was booted from disk, “sinit” checks to see if a normal boot or
an alternate boot occurred. (You can optionally select an alter-
nate boot by pressing
<Esc>
when prompted by the boot loader
during powerup). Based upon this information, “sinit”
attempts to open one of two system initialization files:
a normal boot
“/etc/config/sysinit.n” (where n=node #)
(from disk or
If this fails, it tries:
network)
“/etc/config/sysinit”
an alternate
“/etc/config/altsysinit”
boot (from
If this fails, it tries:
disk only)
“/etc/config/sysinit”
