How to compile your own kernel

Custom Kernel

Article from Issue 250/2021
Author(s):

While not a requirement, compiling the Linux kernel lets you add or remove features depending on your specific needs and possibly make your kernel more efficient.

When people refer to Linux today, they generally mean a Linux distribution, which is composed of the Linux kernel, applications, services, filesystems, and other supporting software. Formally, Linux refers to the Linux kernel, which is the core of all Linux distributions. The kernel manages memory, processes, devices, and system calls. The Linux kernel is the software interface between what we call an operating system and computer hardware.

In this article, you will learn to download, decompress, compile, and install a new Linux kernel onto your system. I'm using a Red Hat Enterprise Linux 8.x system; this procedure should work on all Red Hat Enterprise Linux compatible systems.

Why Compile?

Compiling a Linux kernel is 100 percent optional. Your system will work just fine with a prepackaged Linux kernel. Many enterprises never compile a kernel, and their systems handle workloads without issue.

The primary reason for compiling a kernel is to add features and support that aren't in the kernel by default or to remove some features that are (e.g., virtualization). The kernel, by default, enables virtualization, but not everyone needs or wants this capability. You can selectively remove support for it and work through the compile process to create a leaner kernel that better suits your needs.

Requirements

There are no special skills required to compile a kernel. Although developers use the compilation process, you do not need programming skills. The only skill required is being able to issue commands at a shell prompt and to edit the configuration file should something go amiss during compilation.

You do need root access to the system through sudo, su, or direct login as root. In addition to root access, you need the following prerequisites before compiling the kernel:

  • The Linux kernel source code
  • Sufficient free space on your disk (~20GB or more)
  • Developer Tools suite
  • Developer support packages

Installing Development Tools

You'll need to install the Development Tools bundle and a few extra packages to be able to set up your system and to compile from source code:

# dnf groupinstall "Development Tools"
# dnf -y install ncurses-devel bison flex elfutils-libelf-devel openssl-devel

After the package installations complete, check your system's available disk space (Listing 1).

Listing 1

Checking Available Disk Space

df -h
Filesystem             Size  Used  Avail Use%  Mounted on
devtmpfs               434M     0  434M   0%   /dev
tmpfs                  484M     0  484M   0%   /dev/shm
tmpfs                  484M  6.6M  477M   2%   /run
tmpfs                  484M     0  484M   0%   /sys/fs/cgroup
/dev/mapper/rhel-root   43G   26G   17G  60%   /
/dev/sda1             1014M  433M  582M  43%   /boot
tmpfs                   97M     0   97M   0%   /run/user/1001

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