Generally when most Linux systems are installed, the Grub bootloader program is installed. After Linux installation and computer reboot, the Grub bootloader menu should appear offering the user with a selection of operating systems to boot. The concept is similar to the '''boot.ini''' file that '''NTLDR''' (the boot loader for Windows OS) uses to supply a menu selection for a multiple-boot system.

When the computer system starts, the computer's BIOS locates and runs the bootstrap program on the MBR (Master Boot Record). A series of programs (of Grub) are run provide the user with a selection of operating system to boot. For example, the user can select a version of Linux to load the Linux Kernel, or the user can select another operating system (like Windows) to load in the boot-loader (eg. NTLDR). This process of loading boot loaders for other non-Linux operating systems is referred to as '''chainloading'''.