GRUB - Grand Unified Boot Loader

GRUB's responsibility in the boot process

GRUB2 Installation

There may come a time where you need to install or reinstall GRUB2 on a system. Depending on whether your system is booting via BIOS or UEFI, you'll need to use a slightly different method;

1. BIOS

   The below command can be used to install GRUB2 on a BIOS system (using MBR disks format)
   

   grub2-install [options] /dev/sdX

   Option	Function
   --modules modulenames	Reload specified kernel modules
   --install-modules modulenamess	Install only the specified modules and dependencies.

   
   
2. UEFI
   
   

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GRUBGRUB2 Configuration Options

There are 2 directories to note when talking about GRUB;GRUB2;

/etc/grub - This directory stores configuration scripts that define boot entries for GRUB2.

/boot/grub - This directory stores the actual GRUB2 configuration files used during boot.

There are also 2 commands to note for GRUB configuration:

grubby

• Function: grubby is a command-line tool that allows you to directly manipulate individual GRUB2 menu entries on your system. It provides functionalities for:

  • Setting the default boot entry
  • Adding, removing, or modifying existing entries
  • Changing boot order
  • Viewing information about current entries

• Focus: grubby operates on individual boot entries within the existing GRUB2 configuration.

  
  

   

grub2-mkconfig

• Function: grub2-mkconfig (or sometimes shortened to update-grub on some systems) is a utility used to regenerate the GRUB2 configuration file (grub.cfg) located in /boot/grub. It reads configuration scripts from the /etc/grub.d directory.
• Focus: grub2-mkconfig focuses on rebuilding the entire GRUB2 configuration file based on the defined scripts. This ensures the grub.cfg file reflects any changes made to the configuration scripts in /etc/grub.d.

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