Configuring GRUB for Dual Booting

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Are you tired of dealing with that ***** bootloader every time you turn on your computer?
First things first: what is GRUB and why do we need it? GRUB stands for Grand Unified Bootloader, which basically means that it’s the program responsible for loading your operating system when you turn on your computer. It’s a pretty important piece of software, but unfortunately, it can also be a bit finicky to set up properly.
Now dual booting. If you have multiple operating systems installed on your machine (like Windows and Linux), then you need GRUB to help you choose which one to boot into. Without GRUB, you would have to manually edit the BIOS settings every time you wanted to switch between OSes, which is a pain in the neck.
So how do we configure GRUB for dual booting? Well, it’s not as simple as just installing it and calling it a day (although that might work sometimes). Instead, we need to follow these steps:
1. Install GRUB on your Linux partition. This is pretty straightforward you can use the package manager of your distribution or download the ISO from their website. Once you have GRUB installed, reboot your computer and make sure it’s loading properly (you should see a menu with options for both operating systems).
2. Configure GRUB to recognize your other OSes. This is where things get a bit tricky. You need to edit the grub.cfg file to tell GRUB which partitions contain your other OSes. To do this, open up a terminal and run:

# This line uses the "sudo" command to run the following command with root privileges.
# This is necessary for editing system files.
sudo nano /etc/grub.d/40_custom

# This line opens the 40_custom file in the nano text editor.
# This file is used to configure GRUB to recognize other operating systems.
nano is a command line text editor that allows for easy editing of files.

# The following lines are commented out, meaning they are not active in the script.
# They provide instructions and information for the user.
# It is important to include comments in code to explain its purpose and functionality.

# This line prompts the user to add any custom menu entries below.
# This is where the user will specify the partitions that contain their other operating systems.

# The following lines use the "echo" command to print out instructions for the user.
# They provide guidance on how to properly format the menu entries for GRUB.

# This line uses the "cat" command to display the contents of the 40_custom file.
# This allows the user to see any existing menu entries and make changes if needed.

# Once the user has added their custom menu entries, they can save and exit the file.
# This is done by pressing "Ctrl + X" and then confirming the changes.

# The following line uses the "update-grub" command to update the GRUB configuration.
# This ensures that the changes made in the 40_custom file are recognized by GRUB.

# Finally, the user can reboot their system to see the updated GRUB menu with their other operating systems listed.
# This allows for easy selection of which OS to boot into.

This will open up the custom configuration file in Nano (a text editor). Add the following lines to it:


# This script opens the custom configuration file in Nano, a text editor, and adds lines to it.

# This line creates a menu entry for Windows 10.
menuentry 'Windows 10' {
    # This line sets the root directory to (hd0,msdos5).
    set root='(hd0,msdos5)'
    # This line loads the Windows bootloader.
    chainloader +1
}

Replace “Windows 10” with whatever name you want for your Windows partition (you can also use the UUID instead of the partition number). Save and close Nano.
3. Regenerate GRUB’s configuration file:


# This script regenerates GRUB's configuration file to include any changes made to the system's partitions.

# Use sudo to run the following command as root user.
sudo grub-mkconfig -o /boot/grub/grub.cfg
# The above command generates a new configuration file for GRUB and saves it in the specified location.



# Once the script is executed, the changes will be reflected in the GRUB boot menu the next time the system is restarted.

4. Reboot your computer to test it out! If everything went well, you should see a menu with options for both operating systems when you turn on your machine.
Now some common issues that might arise during this process:
– “Unknown filesystem” error: This usually happens when GRUB can’t find the partition containing your other OSes. To fix it, make sure that the UUID or partition number in your custom configuration file is correct (you can use a tool like GParted to check). If you’re using LVM, then you might need to add some extra lines to your configuration file as well.
– “GRUB rescue” error: This happens when GRUB gets stuck and can’t load properly. To fix it, boot into a live Linux environment (like Ubuntu or Fedora) and run the following commands in a terminal:

# Mount the first partition of the hard drive to the /mnt directory
sudo mount /dev/sda1 /mnt

# Use a for loop to mount important system directories to the corresponding directories in the /mnt directory
for i in /proc /sys /run; do sudo mount --bind $i /mnt$i; done

# Change the root directory to the /mnt directory
sudo chroot /mnt

# Install GRUB to the master boot record of the hard drive
grub-install /dev/sda

# Update the GRUB configuration file to include any changes made
update-grub

Replace “/dev/sda1” with the partition containing your Linux installation. This will reinstall GRUB and regenerate its configuration file, which should fix most issues.
And that’s it! You now have a dual boot system with GRUB configured properly. Congratulations, you’re officially a pro (or at least someone who can follow instructions).

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