Keep the following in mind when you boot a system:
After a system is shut down, it is booted by using the boot command at the PROM level on a SPARC based system or by using the boot command at the Primary Boot Subsystem Menu on an x86 based system.
A system can be rebooted by turning the power off and then back on. This method is not a clean shutdown because system services and processes are terminated abruptly. However, turning a system's power off and back on is an alternative for emergency situations.
SPARC based systems and x86 based systems use different hardware components for booting. These differences are described in Chapter 15, The Boot Process (Reference).