How to Install a Custom Linux Kernel on Arch Linux

The Linux kernel is at the heart of any Linux-based system, responsible for managing hardware, system processes, memory, and more. While the stock kernel provided by Arch Linux is versatile and frequently updated, there are situations where compiling and installing a custom kernel becomes beneficial—or even necessary. Whether you need specific patches, want to strip the kernel down for performance, or are experimenting with kernel development, Arch Linux makes it relatively straightforward to build and install a custom kernel.

This guide walks you through the entire process of installing a custom Linux kernel on Arch Linux, from preparation to compilation and boot configuration.

Why Install a Custom Kernel?

Before diving into the process, it’s helpful to understand why someone might want a custom kernel. Some common reasons include:

• Adding or removing specific drivers
• Applying patches that are not yet merged upstream
• Optimizing for performance by removing unneeded modules
• Testing new kernel versions or experimental features
• Debugging with custom kernel builds

While this isn’t something every user needs, power users and developers often find custom kernels invaluable.

Prerequisites

1. Up-to-Date System

Ensure your Arch system is up to date:

sudo pacman -Syu

2. Install Required Packages

To build a kernel, you’ll need essential development tools:

sudo pacman -S base-devel git ncurses wget bc libelf pahole cpio perl tar xz

3. Sufficient Disk Space

Kernel builds can consume several GBs of space. Make sure you have at least 8 GB free in your working directory.

Step 1: Get the Kernel Source

There are two main ways to acquire the kernel source:

Option A: Download from Kernel.org

You can fetch the official Linux source from https://www.kernel.org.

cd /usr/src
sudo wget https://cdn.kernel.org/pub/linux/kernel/v6.x/linux-6.8.4.tar.xz
sudo tar -xvf linux-6.8.4.tar.xz
cd linux-6.8.4

Option B: Use the Arch Linux Kernel PKGBUILD

Arch packages its kernel using the PKGBUILD format. You can leverage the existing Arch build process as a base for your custom build:

git clone https://gitlab.archlinux.org/archlinux/packaging/packages/linux.git
cd linux

This method is especially helpful if you want to stay close to Arch’s kernel configurations.

Step 2: Configure the Kernel

Option 1: Use the Default Config

Arch uses a configuration found in /proc/config.gz. You can extract and use it:

zcat /proc/config.gz > .config

Option 2: Use make menuconfig

To customize your kernel, use the menu-driven interface:

make menuconfig

This interface allows you to enable or disable kernel options interactively. You can navigate with arrow keys and select/deselect features based on your needs.

Tip: If you’re unsure about a setting, leave it at the default.

Step 3: Compile the Kernel

Now that the configuration is ready, it’s time to compile the kernel.

A. Compile with Make (Manual Approach)

make -j$(nproc)

This will take some time depending on your system’s performance. You can also build the modules:

make modules_install

And finally, install the kernel:

sudo make install

This installs the kernel image (vmlinuz), initramfs, and System.map into /boot.

B. Compile Using makepkg (Arch Way)

If you used the PKGBUILD method, you can edit the configuration inside the build script. Then run:

makepkg -si

This automates the packaging and installation process. You can modify the pkgbase and pkgver in PKGBUILD to distinguish your custom kernel (e.g., linux-custom).

Step 4: Create Initramfs

Initramfs is required for booting. If you built manually:

sudo mkinitcpio -k 6.8.4-custom -g /boot/initramfs-linux-custom.img

Make sure the -k argument matches your kernel version (found using make kernelrelease).

Step 5: Configure the Bootloader

Using GRUB (most common on Arch)

1. Open /etc/default/grub and ensure the following line exists:

GRUB_DISABLE_SUBMENU=y

2. Update GRUB:

sudo grub-mkconfig -o /boot/grub/grub.cfg

GRUB should automatically detect the new kernel if it’s installed in /boot.

Example Entry (If Manual Editing is Needed)

You can manually add a GRUB entry in /etc/grub.d/40_custom:

menuentry 'Arch Linux Custom Kernel' {
    linux /vmlinuz-linux-custom root=UUID=your-root-uuid rw
    initrd /initramfs-linux-custom.img
}

Then regenerate the GRUB config again.

Step 6: Reboot and Test

Once everything is in place:

sudo reboot

At the GRUB menu, select the custom kernel entry if you added one manually. Otherwise, GRUB will list it alongside the stock kernel.

After booting, verify the running kernel:

uname -r

It should display something like 6.8.4-custom.

Optional: Maintain Multiple Kernels

Arch allows you to keep multiple kernel versions installed. This is useful for fallback if something breaks. Just make sure they use different names, such as:

• /boot/vmlinuz-linux
• /boot/vmlinuz-linux-custom
• /boot/vmlinuz-linux-lts

Keep separate initramfs images as well.

Cleaning Up

Kernel source directories and object files take up significant space. You can delete the build directory after confirming that the kernel works properly:

sudo rm -rf /usr/src/linux-6.8.4

If you built with makepkg, you can clean with:

makepkg -c

Troubleshooting

Boot Loop or Panic?

• Try booting into a fallback kernel.
• Double-check your initramfs.
• Ensure your root filesystem UUID is correct in GRUB.
• Review dmesg output or journal logs (journalctl -xb).

Modules Not Loading?

• Confirm that make modules_install succeeded.
• Use modprobe <module> to load manually.
• Check /lib/modules/$(uname -r)/ for presence.

Final Thoughts

Installing a custom Linux kernel on Arch Linux can be a powerful way to tailor your system to your exact needs. Whether you’re looking to optimize performance, add cutting-edge features, or experiment with development, Arch provides a clean and flexible platform to do so.

However, building your own kernel isn’t without risks—so always keep a fallback kernel, backup your data, and take notes during the process. Once mastered, this skill opens up an advanced layer of control and insight into how your Linux system really works.