Grubby: Modifying GRUB Configurations

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We’ll cover everything from installing Grub in various scenarios to troubleshooting common issues that may arise when working with it. Whether you’re running a pure Linux system or setting up a dual-boot with Windows or macOS, this guide will provide you with the knowledge and tools necessary to customize your bootloader experience.

First, let’s discuss why Grub might not be present in some cases. In certain situations, such as when installing an operating system from scratch or using a live CD/USB, Grub may not automatically be installed alongside it. This is because the installation process for these scenarios typically involves booting into a different environment and running commands to manually configure and install Grub.

To install Grub in this scenario, you can use the following command:

bash
# This script installs Grub on a specified device using the sudo command.
# The sudo command allows the user to run commands with administrative privileges.

# The following command installs Grub on the specified device.
sudo grub-install /dev/<device>

# The /dev/<device> is a placeholder for the actual device name, which should be specified by the user.
# This is where Grub will be installed, allowing the device to boot into the desired environment.

# It is important to use the sudo command when installing Grub, as it requires administrative privileges to make changes to the system.


# It is important to double check the device name before running the script to ensure successful installation.

# This script is useful for scenarios where Grub may not be automatically installed alongside the operating system.
# In these cases, the user can manually install Grub using this script to configure and install it on the desired device.

# It is recommended to run this script after booting into a different environment, as it may not be possible to install Grub while the operating system is running.

Replace `` with the device that contains your operating system’s boot partition (e.g., sda). This will install Grub to the specified device and update its configuration accordingly.

Now, modifying Grub configurations using grubby on Linux systems. Grubby is a command-line tool used to display and update information for various bootloaders (including GRUB), including lilo, elilo, zipl, yaboot, and grub itself. It can be used to modify kernel boot entries, check the current configuration, and more.

To view your current Grub configurations using grubby on Linux systems, you can use the following command:

# This script uses the grubby command to view information about a specific kernel in the /boot directory.
# It is commonly used on Linux systems to view Grub configurations.

# The sudo command allows the user to run the following command with root privileges.
sudo grubby --info /boot/vmlinuz-<kernel>
# The --info flag specifies that we want to view information about the specified kernel.
# The /boot/vmlinuz-<kernel> argument specifies the path to the kernel we want to view information about.
# Note: <kernel> should be replaced with the actual kernel version, such as 5.4.0-65-generic.

# The output of this command will include information about the specified kernel, such as its boot entry, root device, and initrd file.
# Example output:
# index=0
# kernel="/boot/vmlinuz-5.4.0-65-generic"
# args="ro quiet splash"
# root="/dev/mapper/ubuntu--vg-root"
# initrd="/boot/initrd.img-5.4.0-65-generic"
# title="Ubuntu 20.04.1 LTS (20.04) 5.4.0-65-generic"

# Note: This script does not make any changes to the system, it simply displays information about the specified kernel.

Replace `` with the kernel version that you want to view. This will display information about the specified kernel, including its boot options and configuration settings.

To modify a specific kernel entry’s boot options using grubby on Linux systems, you can use the following command:

# This script uses grubby to update the boot options for a specific kernel on Linux systems.

# Set the kernel version to be modified.
kernel=<kernel>

# Use sudo to run the grubby command with root privileges.
sudo grubby --update-kernel=$kernel --args="<boot_options>"

Replace `` with the kernel version that you want to modify and `` with the desired boot options. This will update the specified kernel’s configuration settings accordingly.

To remove a specific kernel entry using grubby on Linux systems, you can use the following command:

# This script removes a specific kernel entry using grubby on Linux systems.
# Replace <kernel> with the kernel version that you want to modify.
# Replace <boot_options> with the desired boot options.
# This will update the specified kernel's configuration settings accordingly.

# Use sudo to run the command as root.
sudo grubby --remove-kernel=<kernel>

Replace `` with the kernel version that you want to remove. This will remove the specified kernel from your Grub menu and update its configuration accordingly.

To add new boot options for all available kernels using grubby on Linux systems, you can use the following command:

# This script uses grubby to update boot options for all available kernels on Linux systems.
# Replace <kernel> with the kernel version that you want to remove.
# This will remove the specified kernel from your Grub menu and update its configuration accordingly.

# Use sudo to run the following command with root privileges.
sudo grubby --update-kernel=ALL --args="<boot_options>"
# The --update-kernel flag specifies that we want to update the kernel configuration.
# The =ALL option indicates that we want to update all available kernels.
# The --args flag allows us to specify additional boot options for the kernels.
# Replace <boot_options> with the desired boot options.
# This command will add the specified boot options to all available kernels in the Grub menu.

Replace `` with the desired boot options. This will add the specified boot options to all available kernels in your Grub menu and update their configuration accordingly.

To remove specific boot options for a kernel entry using grubby on Linux systems, you can use the following command:

# This script removes specific boot options for a kernel entry using grubby on Linux systems.
# Replace <kernel> with the desired kernel version.
# Replace <boot_options> with the boot options to be removed.
# This will update the configuration for the specified kernel and remove the specified boot options from its entry in the Grub menu.

# Use sudo to run the command as root.
sudo grubby --update-kernel=<kernel> --remove-args="<boot_options>"

Replace `` with the kernel version that contains the boot options to remove and `` with the desired boot options. This will remove the specified boot options from the specified kernel’s configuration settings.

To add new boot options for a specific kernel entry using grubby on Linux systems, you can use the following command:

bash
# This script uses the grubby command to update the kernel configuration settings by adding or removing boot options for a specific kernel entry on Linux systems.

# The sudo command is used to run the following command with root privileges.
sudo grubby --update-kernel=<kernel> --args="<boot_options>"
# The --update-kernel flag specifies the kernel entry to be updated.
# The <kernel> placeholder should be replaced with the actual kernel entry.
# The --args flag specifies the boot options to be added or removed.
# The <boot_options> placeholder should be replaced with the desired boot options.
# This command will update the specified kernel's configuration settings by adding or removing the specified boot options.
# Note: This command may require additional permissions or privileges to run successfully.

Replace `` with the kernel version that contains the boot options to add and `` with the desired boot options. This will update the specified kernel’s configuration settings accordingly.

To remove specific boot options for all available kernels using grubby on Linux systems, you can use the following command:

# This script uses the grubby command to update the kernel configuration settings for all available kernels on a Linux system.
# It removes the specified boot options from the kernel's configuration.

# Use sudo to run the command with root privileges.
sudo grubby --update-kernel=ALL --remove-args="<boot_options>"
# The --update-kernel flag specifies that the kernel configuration should be updated for all available kernels.
# The =ALL option indicates that the command should be applied to all kernels.
# The --remove-args flag specifies that the specified boot options should be removed from the kernel's configuration.
# The <boot_options> placeholder should be replaced with the desired boot options to be removed.
# This command will update the configuration for all available kernels, removing the specified boot options from each one.

Replace `` with the desired boot options. This will remove the specified boot options from all available kernels’ configuration settings.

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