VMware ESXi and vSphere Cluster Management
Change the Boot Order in BIOS or UEFI
Learn how to boot a Linux installer from USB or CD/DVD by using the one-time boot menu or changing BIOS and UEFI boot priority.
What the boot order does
The boot order, also called boot priority, is the ordered list of devices that your computer's firmware checks when it starts. Firmware looks for bootable software on the first eligible device, then continues through the list if necessary.
Most computers normally start from an internal drive, such as an SSD or hard disk containing the installed operating system. To start a Linux installer from a bootable USB or an optical disc, the removable device must be selected before the internal drive, either temporarily or in the persistent boot order.
BIOS and UEFI terminology
BIOS is legacy motherboard firmware that initializes hardware and begins the boot process. UEFI is the modern firmware interface used by most current computers. UEFI replaces or extends traditional BIOS functionality and can use named UEFI boot entries.
People often say “BIOS” when they mean the firmware setup utility, even on a UEFI computer. Menus differ substantially between manufacturers and motherboard models. Look for labels such as Boot, Boot Priority, Boot Sequence, Boot Options, Startup, and Boot Override.
There are two ways to choose installation media:
- A one-time boot menu selects a device for the current startup without changing the saved default order.
- A persistent firmware boot-priority change changes the saved order until you change it again.
Prepare before changing firmware settings
- Create the Linux installation media from the distribution's ISO file before starting this procedure. A bootable USB must contain the required startup files; copying an ISO file onto an otherwise empty drive is not always sufficient.
- Connect the USB installer or insert the bootable CD/DVD before powering on or restarting the computer.
- Use a direct USB port instead of an unpowered hub when possible. On older hardware, a USB 2.0 port may be detected earlier than a newer USB port.
- Know which device you intend to use: a USB drive, an optical drive, or another removable device.
- Save open work. If the setup key is not recognized, perform a full restart or shutdown rather than relying on a fast-startup transition.
Before changing settings, record the original boot order or take a written note of it. Change only boot-related settings unless you understand the effect of another firmware option.
Common keys for setup and boot selection
| Purpose | Common keys | Important note |
|---|---|---|
| Firmware setup entry | F2, Delete, F10, Esc, sometimes F1 | Press shortly after power-on, before the operating system loads. The manufacturer determines the correct key. |
| Temporary boot menu entry | F12, Esc, F9, F11, or another key | This is separate from the setup key and selects a device for one startup. |
| Save and exit | Often F10, or a Save and Exit menu command | Follow the key legend shown by the firmware and confirm the save prompt. |
The startup splash screen, motherboard manual, computer documentation, or manufacturer support information is authoritative for your device. Begin pressing or tapping the appropriate key immediately after powering on. If you press it after the operating system begins loading, restart and try again.
Use the one-time boot menu
The one-time boot menu is usually the safest and simplest method when you need to start the Linux installer only once. It does not permanently reorder your devices.
- Insert the prepared USB drive or bootable disc.
- Power on or restart the computer.
- Press the manufacturer's temporary boot-menu key during the startup splash screen.
- Use the arrow keys, pointer, or displayed controls to select the USB drive or optical drive.
- Press Enter or choose the command to start the selected device.
On a UEFI computer, the USB may appear twice or may have an entry such as UEFI: USB Manufacturer. When the installation media and target system are intended to use UEFI, choose the UEFI-prefixed entry in preference to a legacy-looking entry.
After selection, the Linux boot menu, live environment, or installer should appear instead of the installed operating system.
Change persistent boot priority
Use this method when you want the removable device to be checked first until you restore the normal order. The exact controls depend on the firmware interface.
- Connect the USB installer or insert the bootable Linux disc.
- Enter the firmware setup utility during startup using the device-specific setup key.
- Open the area labeled Boot, Boot Priority, Boot Sequence, Boot Options, or Startup.
- Identify the removable device. A USB may be listed by its manufacturer or model name, while some systems show a general removable-media category. An optical disc may appear as an optical drive or CD/DVD drive.
- Move the desired USB or optical drive above the internal SSD or hard disk. Use the on-screen key legend, drag-and-drop controls, or plus and minus keys.
- Choose Save and Exit, commonly with F10, and confirm the prompt.
- Allow the computer to reboot and start the installer.
| Method | What it changes | Best use case | What happens after restart |
|---|---|---|---|
| Temporary boot menu | Selects a device for the current boot only. | Starting a Linux installer once. | The saved default order remains unchanged. |
| Firmware boot-priority change | Saves a new order in BIOS or UEFI. | Using a device as the default startup source for multiple boots. | The new order remains until it is changed or overridden. |
Boot device labels
| Actual device type | Possible firmware labels | Selection guidance |
|---|---|---|
| USB installer | USB Storage, Removable Device, the USB manufacturer's name, or the drive model | Choose the entry corresponding to the prepared installer, preferably its UEFI entry on a UEFI installation. |
| CD/DVD installer | Optical Drive, ATAPI CD/DVD, or the optical drive model | Choose the drive containing a disc written as bootable media. |
| Internal SSD or hard drive | Windows Boot Manager, Linux Boot Manager, Internal Storage, or a drive model | This is normally the ordinary installed-system destination after installation. |
| UEFI-specific USB option | UEFI: followed by a USB manufacturer or model name | Use this when the media and intended installation should boot in UEFI mode. |
Save changes and start the installer
A persistent change is not active until it is saved. Select Save and Exit or use the function key shown by the firmware, often F10. Confirm the save prompt and let the machine reboot.
If the removable media is detected and bootable, the Linux boot menu or installer should appear instead of the installed operating system. Follow the installer's instructions. Remove the USB drive or disc when the installer requests it or after installation has completed, so the computer does not restart the installer.
UEFI, Secure Boot, and legacy compatibility
UEFI systems can boot installation media that has been prepared correctly for UEFI mode. Secure Boot is a UEFI security feature that verifies approved boot software before allowing it to start. Many mainstream Linux distributions support Secure Boot, but some media or custom images may not.
Legacy boot is a BIOS-compatible startup mode. CSM, or Compatibility Support Module, is a UEFI feature that can provide legacy BIOS-style compatibility. Legacy or CSM mode may be useful for older hardware or older installation media, but it is not normally needed for current, properly prepared media.
If Secure Boot blocks startup, first use current installation media and verify that it was written correctly. Change Secure Boot only when required by the chosen Linux distribution and hardware, and record the original setting before changing it.
If the USB or disc is missing
Firmware normally lists only devices that it detects and considers bootable. An empty USB drive or incorrectly written drive will not reliably start an installer.
- Power off and reconnect the USB before starting the computer.
- Try another USB port. On older computers, try a USB 2.0 port if a newer port is not detected early in startup.
- Verify that the Linux ISO is the intended image and that the USB was created with a bootable-media creation method.
- For optical media, confirm that the disc was written as a bootable disc rather than containing only the ISO file as ordinary data.
- Try the one-time boot menu as well as the firmware setup device list.
- Test the USB on another computer if you need to determine whether the drive or the original computer is the problem.
- Review UEFI, legacy, CSM, and Secure Boot settings only as necessary for the chosen media.
Troubleshooting common startup problems
The existing operating system starts instead
The removable device may be below the internal drive, the wrong entry may have been selected, changes may not have been saved, or the media may not be bootable. Open the one-time boot menu and explicitly select the USB or optical drive. For a persistent change, confirm that it is above the internal drive, save and exit, and recreate or test the installation media if necessary.
The setup screen does not open
The key may have been pressed too late, or the computer may use a different key. Start pressing or tapping the correct key immediately after power-on, check the splash screen or device documentation, and perform a complete shutdown before trying again if fast startup leaves little time for input.
The USB installer is absent
Reconnect it before startup, try another port, and verify that it was created from a valid Linux ISO using a bootable-media method. If it remains absent, test the drive on another computer and review boot-mode restrictions only when needed.
The computer returns to the installer after rebooting
The installation media may still be inserted, or it may remain first in persistent boot priority. Remove the USB or disc when prompted. If necessary, reopen firmware setup and put the installed internal boot entry, such as a Linux Boot Manager entry, first.
A Secure Boot message prevents startup
The media may be unsigned or incompatible with the current security policy, or it may have been written incorrectly. Use current distribution media, verify and recreate the USB, and review Secure Boot requirements carefully before changing the setting.
Restore ordinary startup after installation
- Remove the USB drive or Linux disc.
- If a one-time boot menu was used, no persistent change is normally required.
- If persistent boot priority was changed and the machine keeps checking external media first, enter firmware setup again.
- Place the intended internal drive or installed operating-system boot manager entry first.
- Save and exit, then confirm that the installed system starts normally.
Key points to remember
- Boot order is the sequence firmware uses to find startup software.
- Use the one-time boot menu when you need to start an installer only once.
- Use Boot Priority or Boot Sequence settings for a persistent change, and save before exiting.
- On a UEFI system, choose the UEFI USB entry when appropriate.
- Secure Boot and legacy or CSM settings can affect compatibility; change them deliberately.
- Changing boot order alone does not erase or install anything.
- Record the original settings and restore the internal boot entry after installation if needed.
For the complete procedure, return to Change the Boot Order in BIOS.