BIOS

BIOS (an acronym for Basic Input/Output System) is a type of firmware used to perform hardware initialization during the booting process (power-on startup) on IBM PC compatible computers, and to provide runtime services for operating systems and programs. The BIOS firmware is built into the motherboard of the computer.

The primary function of the BIOS is to start the computer system and load the operating system into memory. It does this by performing a Power-on self-test (POST) to check if hardware components are working correctly, then locating a bootable device (like a hard drive or optical drive), and finally loading the operating system's boot loader into the computer's RAM.

BIOS has largely been superseded by the UEFI (Unified Extensible Firmware Interface) on modern computers, which provides more features, a more flexible interface, support for larger storage devices, and enhanced security features like Secure Boot. Although technically different, the term "BIOS" is still often used informally to refer to the system's firmware interface, even when it is actually UEFI.

Overview

The BIOS (or UEFI) is the first software that runs when a computer is powered on. Its key responsibilities include:

• Power-on self-test (POST): Initializes and tests basic hardware components like the CPU, RAM, and input/output devices. If POST detects critical errors, it may signal them with beep codes or on-screen messages.
• Initialization: Sets up the system hardware in preparation for the operating system.
• Boot Device Selection: Determines which storage device (e.g., hard drive, SSD, CD/DVD drive, USB drive, network) to load the operating system from based on a configured boot order.
• Loading the Boot Loader: Reads the initial boot program (the boot loader) from the selected boot device and loads it into memory, handing over control to it. The boot loader then typically loads the main operating system.

BIOS vs. UEFI

UEFI is the modern successor to the traditional BIOS. Key differences include:

• Interface: UEFI typically offers a graphical interface controllable by mouse and keyboard, while traditional BIOS usually has a text-based interface navigated only by keyboard.
• Boot Process: UEFI has a more standardized and flexible boot process.
• Disk Support: UEFI supports larger hard drives (over 2.2 TB) using the GPT (GUID Partition Table) partitioning scheme, while traditional BIOS is limited by the MBR (Master Boot Record) scheme.
• Features: UEFI supports networking features within the firmware, has faster startup times, and includes features like Secure Boot to prevent unauthorized operating systems or malicious software from loading during startup.

Accessing BIOS/UEFI Settings

To change boot settings, hardware configurations, or update firmware, you need to access the BIOS/UEFI setup utility.

1. Restart or Power On Your Computer:
2. Watch for the On-Screen Prompt: Immediately after the manufacturer's logo appears (often before the operating system starts loading), look for a message indicating which key to press to enter setup or BIOS. Common keys include:
   • Delete
   • F2
   • F10
   • F12 (Often for a boot device selection menu, not full setup)
   • Esc
3. The exact key varies depending on the motherboard manufacturer (e.g., Dell, HP, Lenovo, Asus, Gigabyte, MSI). Press the indicated key repeatedly as soon as you see the prompt.

1. Alternative for Linux Users (UEFI Systems):

On many modern Linux distributions using `systemd`, you can reboot directly into the UEFI setup from the command line without needing to press keys during startup.

 sudo systemctl reboot --firmware-setup  

This command tells the system to reboot and specifically enter the firmware (UEFI) setup utility. This feature is only available on systems using UEFI, not traditional BIOS.

Changing Boot Settings (Boot Order)

Once inside the BIOS/UEFI setup utility, you can change various settings. One common task is changing the boot order to boot from a USB drive, DVD, or network instead of the primary hard drive.

1. Navigate the Menu:

Use the keyboard (or mouse, if it's a UEFI graphical interface) to navigate through the setup menus. Look for sections labeled "Boot", "Boot Order", "Boot Sequence", "System Configuration", or similar. The layout varies significantly between manufacturers.

1. Locate Boot Priority/Order Settings:

Find the list of bootable devices. You should see entries for your hard drive(s), optical drive(s), USB storage, network boot, etc.

1. Change the Order:

Select the device you want to boot from (e.g., your USB drive) and use the keys indicated on the screen (often F5/F6, +/- keys, or drag-and-drop in UEFI graphical interfaces) to move it to the top of the boot order list.

1. Save and Exit:

Find the "Exit" section of the utility. Select the option to "Save Changes and Exit" or "Exit Saving Changes". Confirm your choice when prompted.

The computer will restart and attempt to boot from the devices in the new order.

Other relevant settings in BIOS/UEFI Boot section:

• Secure Boot: (UEFI only) A security feature that ensures the system only boots using software trusted by the motherboard manufacturer. Can sometimes interfere with booting alternative operating systems and may need to be disabled or configured.
• CSM (Compatibility Support Module): (UEFI only) Allows UEFI systems to boot older operating systems or use older hardware designed for traditional BIOS systems. Enabling or disabling this might be necessary for compatibility.

Updating BIOS/UEFI

Warning: Updating BIOS/UEFI is a process that carries risks. A power outage or interruption during the update can render your motherboard inoperable (bricked). Only perform an update if it is necessary (e.g., to fix a known bug, support new hardware, or improve stability) and always follow the manufacturer's specific instructions precisely.

The general process involves downloading the update file and using a built-in utility within the firmware or a special recovery mode.

1. Identify Your Motherboard:

You need the exact manufacturer and model of your motherboard. You can often find this by checking your computer's documentation, looking for labels on the motherboard itself, or using system information tools in Linux:

 sudo dmidecode -s baseboard-manufacturer  
 sudo dmidecode -s baseboard-product-name  

1. Download the Correct Update File:

Go to the official website of your motherboard manufacturer. Navigate to the support or downloads section. Search for your specific motherboard model. Find the latest BIOS/UEFI firmware version available. Read the description for the update to see what it fixes or adds. Download the update file. Ensure you download the correct file for your *exact* motherboard model and revision number.

1. Prepare the Update Medium (Most Common - USB Drive):

• Get a USB flash drive, preferably one that is not too large (e.g., 8GB or 16GB) and formatted as FAT32. **Back up any data** from the USB drive as it will be erased.
• Format the USB drive (replace `/dev/sdX` with your USB drive's device identifier - BE CAREFUL!):

 sudo mkfs.fat -F 32 /dev/sdX1  # Or /dev/sdX depending on how it's partitioned

• Copy the downloaded BIOS/UEFI file(s) to the root directory of the FAT32 formatted USB drive. If the download was a ZIP or other archive, extract the contents first. Some manufacturers require the file to be renamed (e.g., to a specific name like "BIOS.ROM"). Check the manufacturer's instructions!

1. Access the BIOS/UEFI Update Utility:

Restart your computer and enter the BIOS/UEFI setup utility (using keys like Del, F2, etc., as described above). Look for a built-in utility, often named something like "EZ Flash", "Q-Flash", "M-Flash", "BIOS Update Utility", or "Firmware Update". The location is usually in the "Tool" or "Advanced" sections of the UEFI menu. Some motherboards also allow accessing this utility directly at boot using a specific F-key (e.g., F8 or F12).

1. Perform the Update:

• Select the update utility.
• Choose to update from your USB drive.
• Navigate to the BIOS/UEFI file you placed on the USB drive.
• Select the file and confirm that you want to proceed with the update.
• The utility will likely verify the file.
• The update process will begin. DO NOT turn off or restart the computer during this process. Wait for it to complete entirely. The computer may restart multiple times.
• Once complete, the system will typically restart. You might need to enter the BIOS/UEFI setup again after the update to reconfigure any settings (like boot order) that may have been reset to defaults.

Alternative Update Methods (Less common for Linux-first users):

• Internet Update: Some UEFI firmwares have a built-in network stack and can download updates directly from the manufacturer's servers from within the UEFI utility itself.
• OS-based Utility: Manufacturers sometimes provide Windows-based software to perform the update. This method is generally less recommended due to potential conflicts with the running operating system and is often not available for Linux.

See also

• UEFI
• POST
• Bootstrapping
• Firmware

External links

• Intel: BIOS and UEFI
• How-To Geek: How UEFI Will Replace The BIOS