GRUBkäynnistysvalikossa

GRUBkäynnistys, often shortened to GRUB, is a boot loader package that is commonly used on Unix-like operating systems, particularly Linux distributions. Its primary function is to load the operating system kernel into memory and then hand over control to it. GRUB stands for GRand Unified Bootloader. It is a highly configurable and versatile tool that allows users to select which operating system to boot if multiple are installed on a system, and to pass kernel parameters that can influence the booting process and system behavior.

The GRUB boot loader is typically installed in the Master Boot Record (MBR) or the GUID Partition Table (GPT) of a hard drive. When a computer starts, the BIOS or UEFI firmware first executes the code found in the MBR/GPT, which in turn loads GRUB. GRUB then displays a menu, if configured to do so, allowing the user to choose an operating system from a list of detected bootable entries. If no user input is received within a specified timeout, GRUB will automatically boot the default operating system. GRUB also supports various file systems and can load kernels directly from them, making it very flexible. Its configuration is managed through a text file, commonly named grub.cfg, which defines the boot menu entries, kernel locations, and boot parameters.