how to load kernel in grub command line

Introduction to GRUB Command Line

GRUB or the GRand Unified Bootloader is an essential tool for booting your system. It is a popular boot manager used in Linux operating systems. During the boot process, the kernel loads GRUB, and GRUB provides the user with a menu of choices to boot the system. Apart from the menu, there is also an option to use the GRUB command-line interface. This interface can be used to select and boot the operating system’s kernel manually. In this article, we will learn how to load the kernel from the GRUB command line in a Linux system.

Understanding the Boot Process

Before delving into how to load a kernel from the GRUB command line, it is essential to understand the boot process. When you turn on a computer, the BIOS first initializes the hardware components and then reads the Master Boot Record (MBR) or the EFI System Partition. The MBR or EFI consists of a bootloader (typically GRUB), which loads the kernel and initramfs files from the operating system's /boot directory into memory. The kernel initiates the boot process and brings the system up to the login prompt or graphical interface.

Entering the GRUB Command Line

There are various ways to enter the GRUB command line interface. When you boot your system, the GRUB menu should typically appear on the screen. If not, you can usually force the GRUB menu to appear by pressing and holding the shift key immediately after powering on your system. From the menu, press the 'c' key to enter the GRUB command line. You can also boot into the GRUB command line directly if you have disabled the GRUB menu by editing the grub.cfg file.

Locating the Kernel and Initramfs Files

Before loading the kernel, we must first know the exact path to its location. In most Linux systems, the kernel and initramfs files are located in the /boot directory. You can verify this by pressing the ‘tab’ key after typing ‘linux’ in the GRUB command line. This will show you a list of all the available kernel and initramfs files in the /boot directory. Once you have determined the appropriate filenames and file paths, you can start the boot process by typing ‘linux’, followed by the path to the kernel file, and the initramfs file's path (if any).

Loading the Kernel from the GRUB Command Line

To load the kernel from the GRUB command line, first, enter the command line as mentioned earlier, and then type ‘linux’ followed by the path to the kernel file. For example, if your kernel file is called vmlinuz-5.11.6 and is located in the /boot directory, type ‘linux /boot/vmlinuz-5.11.6’. Once you hit enter, the kernel will start loading. Once the kernel is loaded, you will be prompted with additional commands such as the root device and ro (read-only) options. If necessary, enter the appropriate commands based on your system's configuration.

Conclusion

In conclusion, the GRUB command line interface is a powerful tool for troubleshooting and fixing boot-related problems in a Linux system. We have learned how to enter the GRUB command line interface, determine the kernel and initramfs file locations, and load the kernel from the command line. However, it is always recommended to have a good working knowledge of your system's configuration and backup important data before attempting any changes to the boot process.