GRUB, GRand Unified Bootloader is a powerful bootloader that can load multiple operating systems with chain loading. GRUB is designed to address the complexity of booting a personal computer. It supports a wide variety of OS like Linux, DOS, Windows or BSD. During boot-up, the user can select any required operating system to run.
GRUB is based on an earlier multi-boot package and is most often used on Unix-like systems, including GNU, Linux and Solaris. One can easily configure the GRUB dynamically. This means that the user can make changes and write new boot sequences using a command line i.e. during the boot time. These changes include changing the existing boot entries, selecting different kernels, adding new custom entries, or modifying initrd etc.
In addition it even supports data access in Logical Block Address mode. This means that if your computer has modern BIOS, which is capable of accessing more than 8GB i.e. first 1024 cylinders of hard disk space; even then GRUB is able to access all of it automatically.
Booting with GRUB
GRUB can be easily run from or installed to any device like floppy disk, CD-ROM, hard disk, USB drive or any network drive and can load operating systems from many locations, including network drives. When booting with GRUB, you can use either a command-line interface or a menu interface.
However, one can easily switch between these interfaces. While in the menu interface, user can switch to the command-line mode, and vice-versa. In addition, you can even edit all the menu entries before using them.
Purpose of Designing GRUB
One of the primary requirement or goals for developing the GRUB is to make the bootloader to be compliant with the Multi-boot Specification. Some of the other goals are as listed below:
Features of GRUB
One of the important features of GRUB is its flexibility it is compatible with all file systems and kernel executable formats. Hence, the user can load an arbitrary operating system as needed, even without recording the physical position of your kernel on the disk. Due to this the user can easily load the kernel just by specifying its file name and the drive and partition where the kernel resides. Some of the other features of GRUB are:
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