How to Boot to BIOS on Any Computer or Server

Accessing a system’s BIOS, or its modern successor, UEFI, is typically a matter of timing. The process involves pressing a specific key—commonly F2, F12, or Delete—during the brief interval after powering on the computer, as the manufacturer's logo appears on the screen. This action provides access to the machine's core settings.

Getting to Grips with Your System's Firmware

Before learning how to boot to BIOS, it is helpful to understand the system being accessed. The BIOS (Basic Input/Output System) or UEFI (Unified Extensible Firmware Interface) is the initial software that a computer executes upon startup. It functions as the intermediary between the hardware and the operating system.

Its primary role is to initialize all hardware components—activating the processor, verifying memory, and locating storage drives—before transferring control to the operating system, such as Windows, Linux, or macOS. For IT professionals, including system administrators and advanced users, proficiency in accessing this firmware is an essential skill.

Why Would You Need BIOS Access?

Several critical tasks require access to the firmware settings. Without this low-level access, some of the most common and important system configurations are unavailable.

Common reasons for accessing the firmware include:

• Adjusting the boot order to install a new operating system from a USB drive or a network location.
• Modifying hardware settings, such as enabling or disabling integrated graphics or onboard LAN controllers.
• Enabling virtualization technology (VT-x for Intel or AMD-V for AMD), which is necessary for running virtual machines.
• Monitoring hardware health, including checking system temperatures or adjusting fan speeds to optimize performance.

A common application is the setup of advanced storage configurations, like Hard Drive RAIDs. This is configured directly within the firmware, where multiple physical disks can be combined into a single logical unit to enhance performance or data redundancy.

The Move to Modern UEFI

Although the term "BIOS" is still widely used, most computers manufactured in the last decade utilize UEFI. This modern firmware offers significant advantages, such as faster boot times, support for hard drives larger than 2TB, and improved security features like Secure Boot.

Quick Guide to BIOS vs UEFI Features

Understanding these differences is important, as UEFI has become the industry standard. This knowledge is particularly relevant for administrators managing data centre hardware.

Booting Into BIOS on Windows Desktops and Laptops

On Windows-based desktops and laptops, there are two primary methods for accessing the BIOS or UEFI firmware. The traditional method involves pressing a specific key during startup, while a more modern approach is available directly from within Windows 10 and 11.

Familiarity with both methods is beneficial. The key-press technique may be effective on one machine but challenging on another, particularly with the rapid boot times of modern PCs. The following sections describe each method for learning how to boot to bios on various hardware configurations.

The Classic Keystroke Method

The traditional method for entering the BIOS requires precise timing. A specific key must be pressed on the keyboard immediately after the computer is powered on. This action needs to occur during the short period when the manufacturer's logo (e.g., Dell, HP, ASUS) is displayed, but before the Windows operating system begins to load.

If the Windows logo appears, the opportunity has been missed, and a restart is necessary to try again. A common technique is to repeatedly tap the designated key immediately after pressing the power button until the BIOS screen is displayed.

The specific key varies among different manufacturers and even between models from the same company. However, certain keys are commonly used.

Pro Tip: During the initial boot sequence, the screen often briefly displays a message such as "Press to enter Setup" or "Press for Boot Menu". This message can be easy to miss, so it is important to observe the screen closely.

Common BIOS and UEFI Keys by PC Brand

This reference guide lists the most common keys used by major PC manufacturers to access their BIOS or UEFI settings.

This list is not exhaustive. If these keys are ineffective, consulting the computer's manual or the manufacturer's support website is recommended to identify the correct key for a specific model.

The Modern Software Method: Advanced Startup

Successfully using the keystroke method on a new PC can be difficult. With modern NVMe SSDs, the boot process can be completed very quickly, leaving minimal time to react. The software-based method provides a reliable alternative.

This approach allows the user to instruct Windows to reboot directly into the UEFI firmware settings, eliminating the need to press keys at startup. It is generally the most reliable way to access the BIOS on newer computers.

To access the Advanced startup menu in both Windows 10 and 11:

1. Open the Settings App: Press the Windows Key + I. Alternatively, click the Start menu and select the gear icon.
2. Find the Recovery Options:
   • On Windows 11, navigate to System in the left menu, then click on Recovery.
   • On Windows 10, this is located under Update & Security > Recovery.
3. Start the Process: Locate the Advanced startup section and click the Restart now button next to it.

The PC will then boot into a blue menu screen titled "Choose an option," which is the Windows Recovery Environment.

From this menu, follow these steps:

• First, select Troubleshoot.
• On the next screen, select Advanced options.
• Finally, choose UEFI Firmware Settings. If this option is not visible, the computer may be using an older legacy BIOS, or Windows may have been installed in legacy mode.

After selecting the final option, the computer will restart and boot directly into the BIOS or UEFI interface.

Tackling Firmware on Mac and Linux Machines

While accessing the BIOS on a Windows PC is relatively straightforward, the process differs for macOS and Linux. These operating systems have their own methods for interacting with hardware, but the objective of achieving low-level control over the boot process remains the same.

The process is not more difficult on a Mac or Linux system, but it does follow a different procedure. The following sections detail the specific key combinations and commands required, starting with Apple's recovery environment and then moving to the terminal-based methods available in Linux.

Getting into macOS Recovery and Startup Manager

Apple's design philosophy emphasizes a streamlined user experience, which extends to accessing its firmware equivalent. Instead of a traditional text-based BIOS screen, Macs provide a graphical interface accessed through key combinations during startup. macOS Recovery and Startup Manager serve as the Mac's equivalent to the BIOS.

These tools are used for tasks such as selecting a different startup disk or performing hardware diagnostics.

The following key combinations are important to know:

• Startup Manager (Option/Alt ⌥): Press and hold this key immediately after powering on the Mac. A menu will appear displaying all bootable drives connected to the system. This is used for booting from a USB installer or another external drive.
• macOS Recovery (Command ⌘ + R): This combination provides access to a suite of recovery tools. Users can reinstall macOS, restore from a Time Machine backup, use Disk Utility to repair drive issues, or open a Terminal for advanced troubleshooting.

On newer Apple Silicon Macs (M1, M2, M3, and later), the process is simpler. Press and hold the power button during startup until the startup options screen appears, providing direct access to all necessary functions.

Accessing Firmware on Linux Systems

Linux offers multiple methods for accessing firmware settings. On most modern distributions, such as Ubuntu, Fedora, or Arch Linux, the primary interface is the bootloader, which is typically GRUB (GRand Unified Bootloader).

The traditional method is to access the GRUB menu during system boot. This can usually be achieved by holding the Shift key or pressing Esc immediately after the manufacturer's logo appears. The menu may include an option like "System setup" or "UEFI Firmware Settings," which will launch the firmware interface.

Similar to fast-booting Windows PCs, timing the key press correctly can be challenging. A more reliable method is available for systems that use modern UEFI firmware.

A more effective solution is to use a terminal command. This approach eliminates the need for precise timing and is a preferred method for accessing firmware on modern Linux systems.

Open a terminal and execute the following command:
systemctl reboot --firmware-setup

This command instructs the systemd init system to perform a special reboot that boots directly into the UEFI firmware settings. It is the Linux equivalent of the "Advanced startup" option in Windows and provides a reliable software-based method. For those interested in further optimizing their startup process, it is possible to explore how to optimise boot time with systemd services in Linux. This command is a valuable tool for any Linux administrator.

Entering BIOS on Remote Servers and Virtual Machines

Knowing how to boot to BIOS on a physically accessible machine is one skill, but managing remote servers and virtual machines (VMs) requires different techniques that rely on software tools and specialized hardware interfaces.

These methods emphasize precision and remote control, removing the uncertainty of timing a keystroke from a distance. Mastering these techniques is essential for system administrators, whether for configuring a new virtual environment or performing maintenance on a dedicated server in a data centre.

Gaining Firmware Access on Virtual Machines

When working with virtualization, the "BIOS" to be accessed belongs to the virtual machine, not the physical host computer. Hypervisors—the software that creates and runs VMs, such as VMware or VirtualBox—emulate this firmware, and each has its own method for access.

In VMware products like Workstation or Fusion, the virtual machine often boots so quickly that pressing the required key (usually F2) is difficult. The solution is to either introduce a delay or force a direct boot into the firmware.

This can be accomplished by editing the VM's configuration (.vmx) file and adding one of the following lines:

• bios.bootDelay = "5000": This line adds a five-second delay (5000 milliseconds) to the startup sequence, providing sufficient time to click inside the VM window and press the BIOS key.
• bios.forceSetupOnce = "TRUE": This is a more direct approach. The next time the VM is powered on, it will automatically boot into the BIOS setup screen without requiring a key press.

Oracle's VirtualBox offers a more user-friendly option in its interface. If the VM is configured for EFI, navigate to Settings > System and select the checkbox for Enable EFI (special OSes only). With this setting enabled, pressing F12 during boot will display a boot manager from which "Enter Setup" can be selected.

Using Out-of-Band Management for Dedicated Servers

For physical servers located in a remote data centre, a reliable access method is necessary, even if the operating system is unresponsive. Out-of-band management (OOB) systems provide this capability. These systems operate on a separate, dedicated network connection, offering direct, low-level access to the hardware.

The most common OOB technologies include:

• IPMI (Intelligent Platform Management Interface): A standardized interface for monitoring a server's physical health, power cycling, and accessing a remote console.
• Dell iDRAC (Integrated Dell Remote Access Controller): Dell's proprietary version of IPMI, featuring a web interface and remote management capabilities.
• HP iLO (Integrated Lights-Out): HP's equivalent for their ProLiant and BladeSystem servers, offering similar functionalities.

These tools provide a KVM-over-IP (Keyboard, Video, Mouse over IP) console that streams the server's video output to a web browser while transmitting keyboard and mouse inputs back to the server. This simulates being physically present at the server, allowing the user to observe the entire boot sequence and press the necessary keys to enter the BIOS.

For a system administrator, KVM-over-IP is a critical tool. It can turn an emergency, such as a failed OS boot, from a situation requiring physical presence at the data centre into a problem that can be resolved remotely.

Many hosting providers integrate this functionality into their client control panels. When a dedicated server is provisioned, the client receives access to its IPMI or iDRAC interface, enabling them to manage the firmware, reinstall the OS, and troubleshoot boot issues independently.

This flowchart illustrates the decision-making process for accessing firmware on various systems.

As shown, Mac users utilize specific key combinations, while Linux users have different methods depending on whether their system uses modern UEFI or a legacy setup.

Controlling Firmware on Cloud and VPS Instances

Direct BIOS access is generally not available for a Virtual Private Server (VPS) as it is with a dedicated machine. Since a VPS is a partition of a larger physical server, the cloud provider manages the underlying hardware and firmware.

Providers do offer console access through their client portals. This "no-VNC" or "rescue" console is similar to KVM-over-IP but is typically limited to interacting with the guest operating system. It is useful for tasks such as fixing a firewall rule or a networking issue that has blocked SSH access. For tasks that require firmware-level changes, such as enabling nested virtualization, a support ticket is almost always required.

For those managing their own virtualization platforms, understanding the setup and management is important. You can learn more about setting up KVM virtualisation on your VPS in our comprehensive guide, which provides further information for building a custom cloud environment.

Troubleshooting Common BIOS Access Problems

It can be a frustrating experience when, despite knowing the correct key and method, the system boots directly into the operating system without providing an opportunity to access the firmware. When attempts to boot to bios are unsuccessful, several common issues should be investigated.

A frequent cause is a feature designed to accelerate startup times: Fast Boot. Most modern UEFI firmware includes this setting to reduce boot times by skipping some initial hardware checks. A drawback of this feature is that it often bypasses the brief window during which keyboard input for BIOS access is detected.

The Fast Boot Roadblock

With Fast Boot or its even faster variant, Ultra Fast Boot, enabled, the system may proceed past the point of firmware access before the user can react. Disabling this feature is often the most effective solution.

Since accessing the BIOS is necessary to turn off the feature, a catch-22 situation can arise. The solution is to perform a full shutdown from within the operating system.

• In Windows, navigate to Control Panel > Power Options > Choose what the power buttons do.
• It may be necessary to click "Change settings that are currently unavailable" to proceed.
• Locate the option for Turn on fast start-up (recommended), uncheck it, and save the changes.

This action instructs Windows to perform a complete shutdown rather than a hybrid hibernation. During the next startup, the system will execute a full hardware initialization sequence, increasing the likelihood that the key press will be recognized.

When Your Keyboard or Monitor Is the Problem

Another common issue can be related to the USB keyboard. The firmware may not initialize the USB controllers quickly enough to register keystrokes during the critical boot-up phase.

A simple technique that is often effective is to switch USB ports. Try moving the keyboard from a USB 3.0 port (typically blue) to an older USB 2.0 port (typically black). The drivers for USB 2.0 are often loaded earlier in the boot process, which can resolve the issue.

The monitor can also be a factor. Newer displays with aggressive power-saving modes may take too long to activate. By the time the screen displays an image, the BIOS splash screen may have already passed. If this is suspected, connecting a more basic, older monitor may help determine if the boot screen appears more quickly.

The BIOS Password and CMOS Reset

Forgetting a BIOS or UEFI password can prevent access to the firmware settings. There is no "forgot password" feature in this context. If a password lockout occurs, more hands-on methods are required.

The most direct solution is a CMOS reset. The CMOS is a small memory chip on the motherboard, powered by a small battery, that stores all BIOS settings. Resetting it clears all configurations—including the password—to factory defaults.

There are two primary methods for performing a CMOS reset:

1. Use the CMOS Jumper: Locate a small set of pins on the motherboard, often labeled CLEAR_CMOS, JBAT1, or CLR_PWD. Following the motherboard's manual, move a plastic jumper cap from its default position to the "clear" position for a few moments, then return it to its original position.
2. Remove the CMOS Battery: A simpler method is to completely power down and unplug the machine. Then, carefully remove the small, silver coin-cell battery from its socket on the motherboard. Wait for approximately five minutes before reinserting it.

A CMOS reset is a comprehensive action. It erases all custom configurations, including boot order, fan speeds, and overclocking settings. For complex server setups, diagnosing system behavior after a reset may be complicated and could require checking system-level logs, similar to monitoring kernel logs with dmesg for better VPS management. This method should be used as a last resort.

Answering Your BIOS Boot-Up Questions

Accessing a system’s firmware can raise several questions. The following are answers to some of the most common inquiries related to entering the BIOS.

What's the Real Difference Between BIOS and CMOS?

The terms BIOS and CMOS are often used interchangeably, but they refer to two distinct components.

The BIOS is the software—the firmware program that executes when the computer is powered on. Its function is to initialize and test all hardware before transferring control to the operating system.

The CMOS (Complementary Metal-Oxide-Semiconductor) is the physical memory chip on the motherboard where the BIOS stores its settings, such as the system time, boot order, and hardware configurations. It is powered by a small battery, which allows the computer to retain its settings even when powered off.

The bottom line: When a "BIOS setting" is changed, the BIOS software is used to save the new configuration to the CMOS chip. When a technician refers to "clearing the CMOS," they mean resetting the BIOS settings to their factory defaults.

Is It Risky to Change BIOS Settings?

Yes, modifying BIOS settings can carry risks. These settings control the fundamental operation of the hardware, and incorrect configurations can lead to system instability or prevent the machine from booting.

Particular caution should be exercised with settings such as:

• CPU Voltage (Vcore): Setting this too high can cause permanent damage to the processor.
• Memory Timings and Frequency: Incorrect values can lead to system crashes or a failure to pass the Power-On Self Test (POST).
• Boot Mode (Legacy vs. UEFI): Switching this mode after the operating system has been installed will likely result in a "boot device not found" error.

It is advisable to only change settings that are fully understood. Before making any modifications, taking a photo of the screen with a phone can provide a reference point. If problems arise, look for an option like "Load Optimized Defaults" or "Load Fail-Safe Defaults" to restore the system to a stable configuration.

Why Can’t I See the "UEFI Firmware Settings" Option in Windows?

The absence of the "UEFI Firmware Settings" option in the Windows Advanced startup menu is a common issue. This typically relates to the initial system setup.

This option is only available if Windows was installed in UEFI mode. If the operating system was installed using the older legacy BIOS mode, Windows does not have the necessary interface to trigger a reboot into the modern UEFI firmware.

Additionally, the partition style of the boot drive is a factor. UEFI mode requires the drive to use the GUID Partition Table (GPT). If the drive uses the older Master Boot Record (MBR) format, the option will not be displayed. In these legacy scenarios, the traditional method of pressing the correct key (e.g., F2, Del, or Esc) during startup must be used.