The OpenBoot firmware determines the hardware configuration of a system or virtual machine, provides interactive debugging facilities, prepares memory, and initializes I/O devices by executing their device drivers. OpenBoot also boots the operating system from a storage device or a network if configured to boot.
OpenBoot can be used for other server administration tasks below the OS level. Some devices contain firmware written in the FCode language that enables additional commands which you can enter at the OpenBoot prompt (ok).
The OpenBoot firmware is based on the specification IEEE Standard 1275-1994 for Boot (Initialization Configuration) Firmware: Core Requirements and Practices.
OpenBoot operating characteristics are controlled by configuration variables that are stored in nonvolatile memory (NVRAM). You can change the configuration variable values to tailor operating characteristics to your environment.
See Boot Sequence in Oracle OpenBoot 4.x Administration Guide for more information about booting and boot properties.
The boot process has been enhanced to enable booting from devices that are not directly accessible to OpenBoot. For more information see Boot Pools and Fallback Boot Images in Oracle OpenBoot 4.x Administration Guide.