The BIOS (Basic Input/Output System) was the firmware of choice for each IBM-compatible PC until a few years ago.
In order to configure the system, users need to enter the BIOS setup program by pressing a specific key, such as:
Users can find the right key in their motherboard or computer manual, but it may also be shown at boot time, right after power on. To enter the BIOS setup program, users need to press the right key about two seconds after power on, even if there is no screen displayed.
In the setup program's menu, users can configure several features:
- Enable or disable built-in hardware devices.
- Configure hardware features.
- Set date and time.
- Select boot drives and set a preference order.
- Specify a boot password.
To operate the setup program with a USB keyboard, users may have to enable a function called USB Legacy, or something similar.
Set boot drive and order
Users can use the BIOS setup menu to change the boot drive and to set a preference order. They should set the drive where they installed the bootloader as their first preference, to speed up boot time. It takes time to check optical and floppy disk drives for a valid boot loader, so if those are placed first, the system will not boot as quickly as it might.
For USB boot drives users must enable a function called USB Legacy, or something similar.
Newer BIOS versions let users press a key during boot to open a menu, where they can select the boot drive. This is handy, if they want to boot from a LiveCD. Possible keys are:
Users can find the right key in their motherboard or computer manual, but it may also be shown at boot time, right after after power on. To show the boot option menu, users must press the right key about two seconds after power on, even if there is no screen displayed.
- BIOS Update — describes how to apply a BIOS update on a Gentoo system.
- UEFI — a firmware standard for boot ROM designed to provide a stable API for interacting with system hardware. On x86 it replaced the legacy BIOS.
- Open Firmware — a standard Forth-based firmware popularized by PowerPC Macs which sees continued use with the OpenBIOS project.
- Coreboot — a free and opensource hardware initializing firmware which supports multiple boot ROM payloads.