How to Configure Arch Linux Pacman Hooks to Automatically Recompile DKMS Kernel Modules During Kernel Upgrades

Arch Linux is renowned for its bleeding-edge rolling release model. Users frequently receive major Linux kernel upgrades merely days after they are pushed upstream. While this provides the latest hardware support and security patches, it introduces a severe operational hazard for systems utilizing out-of-tree kernel modules (such as proprietary NVIDIA graphics drivers, ZFS filesystems, or VirtualBox host modules). If the system upgrades the kernel but fails to recompile these specific modules for the new kernel version, the system will catastrophically fail on the next reboot—dropping the user into a black screen or a kernel panic. To guarantee system stability during automated rolling upgrades, Arch Linux administrators must leverage Dynamic Kernel Module Support (DKMS) orchestrated by automated pacman hooks.

The Mechanics of DKMS

When you install a standard kernel module (e.g., via the nvidia package), that module is statically compiled against a specific kernel version (e.g., 6.5.2-arch1-1). If pacman upgrades the system to kernel 6.6.0, the old NVIDIA module cannot be loaded into the new kernel space due to symbol mismatches.

DKMS solves this by storing the raw C source code of the module on your hard drive (typically in /usr/src/). When a new kernel is installed, DKMS automatically invokes the local GCC or Clang compiler, reads the Linux kernel headers for the new version, and dynamically recompiles the module source code into a compatible .ko binary specifically tailored for the new kernel.

Installing the Prerequisites

To facilitate this, you must install the DKMS utility and, crucially, the kernel headers for your specific kernel branch. If you run the default linux kernel, you need linux-headers. If you run linux-lts, you need linux-lts-headers.

sudo pacman -S dkms linux-headers base-devel

Once installed, you must swap your static module packages for their DKMS variants. For example, remove the nvidia package and install nvidia-dkms:

sudo pacman -R nvidia
sudo pacman -S nvidia-dkms

The Role of Pacman Hooks (ALPM Hooks)

Installing DKMS is only half the solution. The pacman package manager must be instructed to automatically trigger the DKMS recompilation process exactly at the right moment during a system upgrade (pacman -Syu). This is handled by Arch Linux Package Management (ALPM) hooks.

By default, the dkms package provides a hook located in /usr/share/libalpm/hooks/70-dkms-install.hook. This hook monitors the pacman transaction stream. It watches for any package upgrade targeting the /usr/lib/modules/ directory (which indicates a kernel upgrade) or any package depending on dkms.

Analyzing the Automation Hook

If you examine the system-provided hook, you will see exactly how the automation operates:

[Trigger]
Operation = Install
Operation = Upgrade
Type = Path
Target = usr/lib/modules/*/vmlinuz
Target = usr/src/*/dkms.conf

[Action]
Description = Install DKMS modules
Depends = dkms
Depends = coreutils
When = PostTransaction
Exec = /usr/share/libalpm/scripts/dkms install

The [Trigger] block instructs pacman to watch for the installation of a new vmlinuz image. If detected, the [Action] block fires during the PostTransaction phase (after the new kernel is safely written to disk but before the pacman command completes).

Pacman executes the shell script defined in Exec. This script iterates through every DKMS module registered in /usr/src/, dynamically recompiles it against the newly installed kernel headers, and securely installs the fresh .ko files into the new kernel’s module tree.

Verifying the Recompilation

To verify the hooks are functioning, you can manually trigger a DKMS status check. This will list all registered modules and the specific kernel versions they are currently compiled against.

sudo dkms status

Output:

nvidia/535.104.05, 6.5.2-arch1-1, x86_64: installed
nvidia/535.104.05, 6.6.0-arch1-1, x86_64: installed

The next time you execute sudo pacman -Syu and a kernel upgrade is present, you will see pacman pause at the end of the transaction, outputting (3/5) Install DKMS modules. The system will consume heavy CPU cycles for a few moments as GCC compiles the C code, mathematically guaranteeing that your proprietary graphics drivers or advanced filesystems are fully compatible and ready to load before you ever initiate a reboot.