During the boot process, the system tests the hardware, loads and executes the operating system, and configures devices. To boot the operating system, the following resources are required:
There are three types of system boots:
| Hard Disk Boot | A machine is started for normal operations with the key in the Normal position. For more information, see "Understanding System Boot Processing". |
| Diskless Network Boot | A diskless or dataless workstation is started remotely over a network. A machine is started for normal operations with the key in the Normal position. One or more remote file servers provide the files and programs that diskless or dataless workstations need to boot. |
| Service Boot | A machine is started from a hard disk, network, tape, or CD-ROM with the key set in the Service position. This condition is also called maintenance mode. In maintenance mode, a system administrator can perform tasks such as installing new or updated software and running diagnostic checks. For more information, see "Understanding the Service Boot Process" . |
During a hard disk boot, the boot image is found on a local disk created when the operating system was installed. During the boot process, the system configures all devices found in the machine and initializes other basic software required for the system to operate (such as the Logical Volume Manager). At the end of this process, the file systems are mounted and ready for use. For more information about the file system used during boot processing, see "Understanding the RAM File System".
The same general requirements apply to diskless network clients. They also require a boot image and access to the operating system file tree. Diskless network clients have no local file systems and get all their information by way of remote access.