MultiBoot

Multiboot refers to a family of specifications and tooling that enables a boot loader to load multiple kernels or operating systems in a controlled, portable way. The most widely used form is the Multiboot specification, originally created by the GNU project to standardize how kernels are loaded by boot loaders such as GRUB.

A kernel that wants to be bootable under Multiboot includes a Multiboot header in its binary. The boot loader loads the kernel, passes a set of boot information (such as memory map, command line, modules), and transfers control to the kernel's entry point. There is Multiboot1 and Multiboot2; Multiboot2 provides additional features and a more robust interface. The specification defines a common header, data structures, and conventions to ensure compatibility between boot loaders and kernels.

Multiboot is commonly used to enable multiboot menus, allowing users to select between different operating systems or kernel configurations at boot time. GRUB, Syslinux, and other boot loaders support Multiboot. While many Linux distributions and other kernels offer Multiboot support, not all OS kernels are built to Multiboot, and Windows uses its own boot mechanism and is typically not Multiboot compliant.