Lesson 1	Linux Kernel Configuration and Compilation: Introduction
Objective	Choose an appropriate kernel-management approach and explain the module's build and verification workflow.

Linux Kernel Configuration and Compilation: Introduction

The Linux kernel manages CPU time, memory, devices, filesystems, and networking. Applications use its services through system calls; desktop environments, shells, and network servers run mainly in user space. A graphical desktop is therefore not a feature that every kernel must contain.

This module explains how to inspect and configure kernel modules, decide whether a custom kernel is justified, and carry a source build through installation and verification. Administration examples use Red Hat Enterprise Linux (RHEL) 10. The source-build exercises describe an upstream Linux kernel in a disposable x86-64 lab; they are not instructions for replacing a supported RHEL kernel on a production server.

Choose the smallest necessary change

A missing capability does not automatically require compilation. Start by identifying the running kernel and checking whether the required feature is already built in, available as a module, or controlled by a documented runtime setting. For a normal RHEL kernel update, use the distribution's signed packages and maintenance procedure. Installing an update and booting it are separate operations.

uname -r
uname -m
cat /etc/os-release
rpm -q kernel-core

Record these results before making changes. The release printed by uname -r identifies the kernel executing now, which may differ from the newest installed kernel. Later lessons use a separate target release when preparing a custom kernel that has not yet booted.

What you will learn

Explain why Linux can be both monolithic in architecture and modular in configuration.
Distinguish installed modules, loaded modules, and built-in functionality.
Use modinfo, lsmod, and modprobe for different administrative questions.
Configure module options and deliberate boot-time loading.
Evaluate the benefits and maintenance costs of a custom kernel.
Prepare source, tools, storage, and a recoverable lab environment.
Create and review a kernel configuration.
Build and install the kernel with its matching modules.
Verify the target initramfs, boot entry, and post-boot behavior.
Manage RHEL boot entries with current tools and retain a working fallback.

Follow the build as a sequence

A kernel build has four distinct stages: configuration chooses features; compilation creates binaries; installation places artifacts where the system expects them; booting activates the selected kernel. A successful compiler exit does not prove that the machine can find its root filesystem or that its network works.

Use a virtual machine with a snapshot and console access for the lab. Preserve its known-good kernel, modules, and boot entry. Secure Boot and module-signature policy must be considered before installation: a binary can compile successfully and still be refused by the boot chain or running kernel.

The next lesson establishes the distinction between kernel architecture and loadable modules.

References