TestOut Linux Pro Practice Test 2025 – All-in-One Guide to Master Your Certification!

To apply changes made to the GRUB configuration, the command `grub2-mkconfig -o /boot/grub/grub.cfg` is necessary because it generates a new grub.cfg file using the current configuration settings. This command effectively combines the settings specified in the `/etc/default/grub` file and any scripts found in the `/etc/grub.d/` directory to create or update the boot menu configuration file.

This generated `grub.cfg` is what the GRUB bootloader reads when the system starts to display the available operating systems and their options. Without executing this command after modifying the configuration, any changes made will not take effect until the new configuration is generated and saved.

Other commands mentioned, like `update-grub` and any fictitious options, may not specifically generate and output the grub.cfg in the required manner, particularly with the correct syntax and target file. `update-grub` serves as a convenience script that typically calls `grub-mkconfig` under the hood, but directly using `grub2-mkconfig` provides more explicit control over the output file.