Where to learn GRUB commands?

Question

First of all is the GRUB essential to have Ubuntu?

If yes, where can I learn it's commands? It makes me dead when it stops booting Linux and displays dangerous prompts.

And is there any good Graphical UI for grub?

Answer 1

is the GRUB essential to have Ubuntu?

GRUB is the boot loader (and Ubuntu loader) program which loads Ubuntu from the disk to the Memory to be run. So, yes, Such a program is essential to have Ubuntu and it is Grub by default. But there are other bootloader too, such as LILO (LInux LOader) and recent BURG.

Grub is only essential to boot Ubuntu, not for Ubuntu users to learn. But You might want to know some of the basics of Grub for odd situations.

To learn Grub, You can use the Grub manual here : manpage for the grub command

I recommend you to read the GNU info pages, those are very extensive and helpful. To view it, write info grub in a terminal.

There is a graphical front-end for Grub, called Grub-customizer. It is on a PPA. To install it, execute these commands one by one in a terminal:

sudo add-apt-repository ppa:danielrichter2007/grub-customizer
sudo apt-get update
sudo apt-get install grub-customizer

You may be asking this question for knowledge about repairing grub. To simplify your task, there is a boot-repair program which is very handy.

To install it, Use these commands:

sudo add-apt-repository ppa:yannubuntu/boot-repair && sudo apt-get update
sudo apt-get install -y boot-repair

Also take a look at this page for a general introduction to boot repair: https://help.ubuntu.com/community/Boot-Repair

Answer 2

GRUB 2 is the default boot loader and manager for Ubuntu since version 9.10 (Karmic Koala). As the computer starts, GRUB 2 either presents a menu and awaits user input or automatically transfers control to an operating system kernel. GRUB 2 is a descendant of GRUB (GRand Unified Bootloader). It has been completely rewritten to provide the user significantly increased flexibility and performance. GRUB 2 is Free Software.

In this guide, GRUB 2 is version 1.98 or later. GRUB legacy (version 0.97) will be referred to as GRUB. To determine your version, use grub-install -v. Grub version 1.99 became the default on Ubuntu 11.04 (Natty Narwhal) and introduced some major changes in the Grub file contents. This guide covers the use of Grub 1.98, the Grub release found in Ubuntu 10.04 LTS (Lucid Lynx). and Grub 1.99, packaged with Ubuntu 12.04 LTS (Precise Pangolin). Content reflecting other versions of Grub 2 will be noted in the appropriate entry.¹

Other resources:

GNU GRUB Manual 0.97

GRUB - COMMAND LIST

GRUB bootloader - Full tutorial

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