Power-on self-test keys

The power-on self-test (POST) keys can start services or initiate service mode boots used for configuring the system and diagnosing problems.

After power is turned on and before the operating system is loaded, the system does a power-on self-test (POST). This test performs checks to ensure that the hardware is functioning correctly before the operating system is loaded. During the POST, a POST screen is displayed, and POST indicators appear on the firmware console (if one is connected).

Numeric 1 key

The numeric 1 key, when pressed during POST, starts the system management services interface.

Numeric 5 key

The numeric 5 key, when pressed during POST, initiates a system boot in service mode using the default service mode boot list.

This mode attempts to boot from the first device of each type found in the list. It does not search for other bootable devices of that type if the first device is not bootable. Instead, it continues to the next device type in the list.

The default boot sequence is:

1. CD-ROM (if installed)
2. Tape drive (if installed)
3. Hard file
4. Network

Numeric 6 key

The numeric 6 key works like the numeric 5 key.