SPARC: OpenBoot - Disable Auto-Boot?
Abstract:
SPARC based platform have a level of firmware between the chassis hardware and the loaded OS called OpenBoot, The IEEE created a standard based upon it, IEEE 1275-1994, and it was called OpenFirmware. Sun Microsystem's OpenBoot was released as Open Source in 2006 under a BSD license, and other vendor implementations were also released. The persistent settings for OpenBoot are held in the environment, as well as defaults, and changes can be made to the EEPROM. The Auto-Boot? environment value is one typical value commonly adusted.
Achieve Console
Console can be achieved on a typical rack mount system via TCP/IP connection to the ILOM, with a command to grab the console to the OK prompt (assuming the autoboot flag is disabled.)
The Environment
The environment consist of a series of label-value pairs. Those labels define the characteristics by which the behavior of the chassis can be modified during any changes.
Show OpenBoot Environment Values & Defaults
The printenv command shows a copy of all label-value pairs, as well as defaults.
Set an AutoBoot Environment
The autoboot flag, in the above example, is currently enabled, which is also the default value.
This can be disabled, for the purpose of loading a new OS after a fresh reboot.
Conclusion:
Environment Label-Value pairs in OpenBoot drive the behavior of the firmware. This value can be set to true, to force boot on chassis power up, or to leave the OS at the "ok" prompt on power up. This is definitively helpful in an environment where a failure may take a chassis down unexpectedly, VM's were brought up on an alternate chassis, and repair of the failued chassis environment is not desirable to bring up the OS formerly running on the failed chassis until an orderly transition can be enabled.