New Skills

New Training: Explain Linux Kernel and Boot Concepts

by Team Nuggets
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Published on February 19, 2021

In this 8-video skill, CBT Nuggets trainer Shawn Powers explains the Linux boot process, including UEFI and BIOS, the Grub bootloader, and kernel modules. Watch this new Linux training.

Watch the one of these courses:

This training includes:

  • 8 videos

  • 43 minutes of training

You’ll learn these topics in this skill:

  • BIOS and UEFI

  • GRUB and GRUB2 Bootloaders

  • Boot File Locations

  • Boot Methods

  • Boot Modules and Files

  • Kernel Panic

  • Loading Kernel Modules on Boot

  • Manipulating Kernel Modules

The Linux Boot Process in 6 Steps

The Linux boot process is straightforward and consists of six main steps:

  1. BIOS: The Basic Input/Output System kicks on first, loading and then executing the Master Boot Record boot loader. It performs integrity checks on the hard drive, then detects the boot loader program and loads it into the memory.

  2. MBR: The Master Boot Record loads and executes the GRUB boot loader. It is located in the first sector of the bootable disk.

  3. GRUB: In very old systems, this was the LILO. In modern systems, the GRand Unified Bootloader offers a simplified menu that allows you to select the kernel image you want to boot with (if you have more than one installed). The default kernel image is the latest one installed.

  4. Kernel: This is the core of an operating system and controls everything within it. Once the GRUB selects it, the kernel mounts the root file system and then executes the /sbin/init program. The temporary root file system is established until the real file system can be mounted.

  5. Init: Linux will choose one of six run levels to execute: 0, 1, 3, 5, 6, or Emergency.

  6. Finally, Linux will execute runlevel programs which are executed from various directories (0 through 6).

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