What is GRUB

what is grub

GRUB is one of the bootloaders that are necessary for your operating system to boot up. The powerful and adaptable grand universal bootloader, or GRUB, is a tool used to boot operating systems’ kernels.

It functions as the system’s default bootloader when it comes to Linux-based systems. Even so, a lot of computer nerds are still confused about what GRUB is. We will cover all you need to know about the GRUB in this guide.

GRUB: What Is It?
The bootloader program, GRUB, allows the user to choose which installed operating system or kernel to load when the system boots up. After turning on and loading the kernel into memory, GRUB runs the kernel. Following that, you can choose which of the many operating systems you wish to boot. As a result, GRUB serves as both a boot manager and a bootloader. Let’s examine some of GRUB’s characteristics to gain a better understanding of it.

GRUB’s characteristics

  • It operates autonomously without human input.
  • Every time it is modified, there’s no need to write the configuration file again.
  • The operating system loads from many areas.
  • Before starting the operating system, GRUB decompresses it.
  • It can be installed and used on a variety of hardware, such as hard drives, USB drives, CD-ROMs, DVDs, and floppy disks.
  • GRUB’s dynamic configuration lets users make changes while the system is booting up.
  • It is possible to create an infinite number of boot entries

GRUB versions
There are now two primary versions of GRUB available, and they are as follows:

GRUB Legacy, Initial Version

In 1995, they launched the initial iteration of GRUB. Originally created by Erich Stefan Boleyn, it is a multiboot bootloader that is now maintained by the GNU Project.

Version 2 of GRUB

The most popular version of GRUB is GRUB 2. It is available for use with Linux distributions like Fedora, Ubuntu, Manjaro, and Red Hat Enterprise Linux (RHEL). Compared to version 0, it offers more tools and setting possibilities.

How Is GRUB Operational?
An options menu featuring a list of Linux kernels and operating systems is offered by GRUB. You can use this menu to select the options that best suit your needs. For your reference, an image of the GRUB menu list is attached.

GRUB boots the chosen kernel after the booting system has been chosen from the preceding menu. Its parameters are distinct. The following are the functions of these parameters during operating system boot:

kernel discovers the kernel’s location.
burst The splash screen appears when the computer is booting up.
calm While the system is starting, it conceals a few notifications relevant to the system.
BOOT_IMAGE Where the Linux kernel image is located.
To The file system is mounted in read-only mode.
root It is where the root filesystem is located.
initrd Names the first RAM disk.

The items in the GRUB menu are determined by the configuration that the Linux distribution has specified. To modify a GRUB menu item, press the “e” key in the GRUB menu interface. Before loading, you can modify the kernel parameters. The “c” key can also be used to access the GRUB command line menu.

Even after the Linux distribution upgrades the kernel version, it retains at least one earlier version. If you experience any problems with the updated version, it does this to boot into an older version of the Linux kernel.

Eventually, you will see an entry labeled “UEFI settings” or “System setup,” which gives you access to your computer’s BIOS settings.

Methods for Setting Up the GRUB
Any modifications you make to GRUB using the menu interface are temporary. You have to edit the configuration file after booting into the Linux system if you want to make permanent changes to GRUB, such as altering the default timeout.

Grub.cfg, the primary GRUB configuration file, is kept in the /boot/grub directory. It’s not advised to alter this file directly. As an alternative, you can modify the /etc/default/grub GRUB configuration file. By include the.cfg config file in this directory, you can make further modifications. The directory /etc/default/grub.d is also present.

The /etc/default/grub can be modified by using the following command:

$ sudo update-grub

This enables you to automatically update the grub.cfg file with your modifications.

The following command can be used to get more details about GRUB:

$ info -f grub

 

 

Final
When a computer boots up, the bootloader is the first piece of software to run. You must now understand that GRUB is an extremely capable and adaptable boot loader, and that the user has total control over the boot screen.

GRUB is a rather large topic. This article’s goal is to give all the information that is required. Details like the features, versions, and setup of GRUB were covered in this guide.

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