The input-device and output-device variables control the firmware's selection of input and output devices after a power-on reset. The default input-device value is keyboard and the default output-device value is screen. The values of input-device and output-device must be device specifiers. The aliases keyboard and screen are often used as the values of these variables.
When the system is reset, the named device becomes the initial firmware console input or output device. (If you want to temporarily change the input or output device, use the input or output commands described in Chapter 4, Using Forth Tools)
ok setenv input-device ttya ok
If you select keyboard for input-device, and the device is not plugged in, input is accepted from a fallback device (typically ttya) after the next power cycle or system reset. If you select screen for output-device, but no frame buffer is available, output is sent to the fall-back device after the next power cycle or system reset.
ok setenv output-device /sbus/SUNW,leo ok