bootmenu

Boot menu, in computing, refers to a user interface presented during the early stages of system startup that allows the selection of a boot device, operating system, or other startup options. The menu is typically provided by the platform firmware or by a bootloader. It is used to initiate multiboot configurations, perform recovery operations, or load diagnostic tools.

Boot menus come in two main forms. The firmware-provided boot menu appears before an operating system loads and is invoked by a hardware key during POST, such as F12 or Esc on many PCs. UEFI systems rely on the UEFI Boot Manager, which uses firmware NVRAM entries to present a list of boot options. The other form is a bootloader menu, generated by programs such as GRUB, LILO, or Systemd-boot, which resides on disk and can offer a more complex, configurable menu with submenus and kernel parameters.

Typical features include a timeout, a default entry, support for editing kernel parameters, password protection, and the ability to chainload other bootloaders. Some entries may be hidden or password-protected for security or maintenance reasons.

Security considerations include Secure Boot, which verifies signatures before loading components, and the risk that compromised bootloaders or misconfigured menus can bypass OS protections. Best practices emphasize keeping firmware and bootloaders updated, using signed bootloaders, and carefully configuring multiboot setups.

Notable examples of boot management software include GRUB, Systemd-boot, rEFInd, and Windows Boot Manager, alongside legacy options like LILO. In virtualization, boot menus aid in selecting guest operating systems or recovery tools.