dualboot

Dual-booting is the setup where two or more operating systems are installed on one computer, allowing the user to choose which OS to load at boot. This is typically done by creating separate partitions for each system and by installing a bootloader that presents a selection menu when the computer starts.

Bootloaders such as GRUB, Windows Boot Manager, or rEFInd load at startup and chain to the selected OS. The bootloader reads a configuration file that points to each system's kernel and initial ramdisk, or to the Windows boot files, and may provide recovery or advanced options.

Common pairings include Windows with a Linux distribution, or between two Linux installations. On Apple hardware, dual-booting between macOS and Windows is commonly done using Boot Camp; newer Macs may use EFI-based loaders or virtualization as alternatives.

Setup considerations include partitioning with GPT for UEFI systems, creating an EFI System Partition, and planning installation order. Windows often requires its own NTFS partition; Linux distributions usually need a root partition with optional swap. Some setups share a data partition to access files from both systems. Security features such as Secure Boot can affect a bootloader, and may need adjustment or disabling.

Benefits of dual-booting include access to software and environments available only on another OS, and the ability to repurpose hardware for different tasks. Risks include bootloader repair after OS upgrades, potential data loss if partitions are misconfigured, and updates that overwrite the bootloader. Alternatives include virtualization or running live environments for testing.