A number of OpenBoot operating characteristics are controlled by configuration variables that are stored in nonvolatile memory. The list of configuration variables varies from system to system.
These variables determine the start-up configuration and related communication characteristics. You can modify the values of the configuration variables, and any changes you make remain in effect even after a power cycle.
Most configuration variables have both a current value and a default value, with the default value stored in ROM. OpenBoot implementations can maintain a checksum of the nonvolatile memory used for configuration variable storage. If that memory becomes corrupted, the OpenBoot implementation can restore some of the configuration variables to their default values, leaving untouched those configuration variables without default values.
The nonvolatile memory locations where particular parameter values are stored can change from machine to machine and from revision to revision. Thus, they cannot be accessed at fixed locations, but instead must be accessed by name. You can access them by name using printenv and setenv. Client programs can access them by name through client interface operations on the /options device node.
The properties of the /options node are the virtual machine's configuration variables. The property names are the names of those configuration variables, and the property values are the output text representations of those configuration variables. Client programs can examine and change the values of these properties with getprop and setprop, thus examining and changing the values of the corresponding configuration variables. Similarly, you can examine and change them with printenv, setenv, and $setenv commands.
Use these topics to understand the standard configuration variables and the commands that you can use to modify the configuration variables.