Picking an OS to Boot Boot Loaders

On a single-OS computer, the boot process is fairly straightforward—on IA-32 systems, the BIOS searches for code on the hard disk's (or other bootable disk's) boot sector, aka the Master Boot Record (MBR), which is the first sector on the disk. This code is often called the primary boot loader, and in some cases, it directs the boot process to just one OS or to any OS you select. In other cases, the primary boot loader relies on a secondary boot loader, which may reside in a partition of its own (as in OS/2's Boot Manager) or in the boot sector of a specific partition, in order to finish the job.

Three boot loaders ship with most Linux distributions: the Grand Unified Boot Loader (GRUB), the Linux Loader (LILO), and LOADLIN. Writing a Linux kernel directly to a floppy disk using dd and booting using the floppy is also possible, provided your kernel fits on a single floppy disk (it might not). This approach is useful for emergency situations and for testing a new kernel. Various third-party boot loaders are available, and you may want to use one of them. These tools require the help of GRUB or LILO (installed in a partition's boot sector) to boot Linux.

Note This section describes boot loaders for IA-32 computers. Other architectures have their own boot loaders, such as Yaboot

(http://penguinppc.org/proiects/yaboot/) for PowerPC machines. The basic principles of configuring these tools are similar to those for LILO or GRUB, but many details differ.

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