Boot process
There are three types of system boots and two resources that are required in order to boot the operating system.
During the boot process, the system tests the hardware, loads and runs the operating system, and configures devices. To boot the operating system, the following resources are required:
- A boot image that can be loaded after the machine is turned on or reset.
- Access to the root (/) and /usr file systems.
There are three types of system boots:
| Item | Description |
|---|---|
| Hard Disk Boot | A machine is started for normal operations. |
| Diskless Network Boot | A diskless or dataless workstation is started remotely over a network. A machine is started for normal operations. One or more remote file servers provide the files and programs that diskless or dataless workstations need to boot. |
| Maintenance Boot | A machine is started from a hard disk, network, tape, or CD-ROM in maintenance mode. A system administrator can perform tasks such as installing new or updated software and running diagnostic checks. |
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.
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.