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Migrate to GRUB 2

Apr 16, 2010, 12:33 (0 Talkback[s])

"To most people, boot loaders aren't the most exciting aspect of an operating system, but they are extraordinarily important. Without a functioning boot loader, nothing else works. Currently, a transition from the old Grand Unified Bootloader (GRUB) Legacy tool to the new GRUB 2 is underway. GRUB 2 is the default boot loader in Ubuntu 9.10, and it's an option in most other major Linux distributions. Sooner or later, other distributions will deploy GRUB 2 as the default boot loader.

"Anatomy of a boot loader

"Figure 1 shows the boot process as implemented by both GRUB Legacy and GRUB 2. The basic input/output system (BIOS) is the first code to run on the computer, and it's stored in the computer's firmware. The BIOS loads the first sector of the boot device and executes the code it contains. In the case of a hard disk, this first sector is also known as the master boot record (MBR), and it contains both the first stage of the boot loader and the MBR partition table. Because most disk devices use a sector size of 512 bytes, the first-stage boot loader code must be very small. Most boot loaders, including both GRUB Legacy and GRUB 2, place additional code elsewhere on the disk. In the case of GRUB Legacy, this additional code is known as stage 1.5, and it's often placed in an unallocated area immediately following the MBR. Still more code, known as stage 2, is stored in files in the Linux boot partition (typically in the /boot directory), although Figure 1 omits these files for simplicity's sake. Likewise, in a multiple-operating system configuration, the secondary boot loader may store additional configuration files elsewhere."

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