A system reboot is a shell script that recopies the operating system from disk to memory and starts it without turning the system completely off. A reboot is also known as a system reset. It reinitializes the operating system by repeating the initial program load (IPL) operation. When the system is first turned on, the operating system is usually booted automatically.
The reboot command is used if no other users are logged into the system. Reboot to cause the system to recognize newly installed software, to reset peripheral devices, to perform routine maintenance tasks like checking file systems, or to recover from a frozen system or a system crash. The shutdown command is used instead of the reboot command when the system is running and multiple users are logged into the system.
Use the reboot command to reboot the operating system when it is accessed by only one user. The reboot command synchronizes the hard disks and performs some other shutdown activities without halting the system.
The steps that take place during a system reboot depend on how the system was customized. The reboot process described in this section may not be exactly the same on your system.
Note: You must have root user authority to reboot the system.