Bootstrapping is the process of loading and executing the bootable operating system. Typically, the stand-alone program is the operating system kernel, but any stand-alone program can be booted. After the kernel is loaded, it starts the UNIX system, mounts the necessary file systems, and runs /usr/sbin/init to bring the system to the initdefault state that is specified in the /etc/inittab file.
Keep the following guidelines in mind when booting a system:
After a SPARC based machine system is shut down, it is booted by using the boot command at the PROM level. After a SPARC based system is turned on, the system firmware (in PROM) executes a power-on self-test (POST). The form and scope of these tests depends on the version of firmware in your system. After the tests have successfully completed, the firmware attempts to auto boot, if the appropriate flag has been set in the non-volatile storage area that is used by the firmware. The name of the file to load, and the device to load it from, can also be manipulated.
An x86 based system is booted by selecting an operating system in the GRUB menu that is displayed at boot time. If no operating system is selected, the system boots the default operating system that is specified in the grub.cfg file.
A system can also be rebooted by turning the power off and then back on.