At power on, the boot prom performs the Power On Self Test (POST). Once this is done, you see the banner logo (oem-logo) and banner text (oem-banner).
The boot prom then looks for the boot-device. The boot-device is set using the OpenBoot setenv command, and point to an alias created with nvalias, so that you can issue the command boot disk instead of having to use the long device name.
The boot prom also reads the content of the boot-file variable, which points by default to kernel/unix.
From the boot device, the boot prom reads and loads the boot block.
With this information, the boot prom can start the secondary bootprogram, ufsboot.
This program loads the kernel.
The kernel reads /etc/system to check which drivers (modules) have to be loaded and what options need to be set. Options may be such lines as set rstchown=0, which enables non-privileged users to apply the chown command. Other settings include special configurations for installing databases, for using software RAID, etc.
The kernel initializes and loads the modules.
The kernel starts init.
Init reads /etc/inittab and finds the default run level.
The /sbin/rcx script for this run level is read and scripts in /etc/rcx.d are executed.