Features of GRUB

A number of features make GRUB preferable to other boot loaders available for the x86 architecture. Below is a list of some of the more important features:

• GRUB provides a true command-based, pre-OS environment on x86 machines. This affords the user maximum flexibility in loading operating systems with certain options or gathering information about the system. For years many non-x86 architectures have employed pre-OS environments that allow system booting from a command line. While some command features are available with LILO and other x86 boot loaders, GRUB is more feature rich.

• GRUB supports Logical Block Addressing (LBA) mode. LBA places the addressing conversion used to find files in the hard driver’s firmware, and it is used on many IDE and all SCSI hard devices. Before LBA, boot loaders could encounter the 1024-cylinder BIOS limitation, where the BIOS could not find a file after that cylinder head of the disk. LBA support allows GRUB to boot operating systems from partitions beyond the 1024-cylinder limit, so long as the system BIOS supports LBA mode. Most modern BIOS revisions support LBA mode.

• GRUB can read ext2 partitions. This allows GRUB to access its configuration file, /boot/grub/grub.conf, every time the system boots, obviating the need for the user to write a new version of the first-stage boot loader to MBR when configuration changes are made. The only time a user would need to reinstall GRUB on the MBR is if the physical location of the /boot partition is moved on the disk. For details on installing GRUB to the MBR, see the next section.