Solved: Attempting to Install and Configure Wireguard Fails with “Unknown device type” and “FATAL: Module wireguard not found in directory”

My Problem

Attempting to install and use Wireguard (version 0.0.20190406-1) on Fedora release 29 is unsuccessful with a variety of symptoms. The first being:

ip link add dev wg0 type wireguard
Error: Unknown device type.

Attempting to get some info about the module with modprobe shows:

$ modprobe wireguard
modprobe: FATAL: Module wireguard not found in directory /lib/modules/5.0.4-2004

The dkms tool shows that the wireguard module is added:

$ dkms status
wireguard, 0.0.20190406: added

However, attempting to build it shows:

$ dkms build wireguard/0.0.20190406
Error! echo
Your kernel headers for kernel 5.0.4-200.fc29.x86_64 cannot be found at /lib/modules/5.0.4-200.fc29.x86_64/build or /lib/modules/5.0.4-200.fc29.x86_64/.

My Solution

Make sure that your running kernel and your kernel headers are the same version, or at least that the running version of the kernel is newer than your kernel headers.

For example, I’m running on a RedHat based system, and checked the following:

$ uname --kernel-release
5.0.4-200.fc29.x86_64

But then the kernel headers were newer:

$ rpm -q kernel-headers
kernel-headers-5.0.9-200.fc29.x86_64

My solution was to yum update the kernel and reboot. I didn’t have to re-install the headers or the wireguard packages. Another possible solution would have been to manually install 5.0.4 kernel headers, but that would require uninstalling packages that marked 5.0.9 kernel headers as a dependency. I believe the cleaner solution is to simply update the kernel.

The Long Story

First, I checked that I even had kernel headers installed in the first place:

$ rpm -q kernel-headers
kernel-headers-5.0.9-200.fc29.x86_64

Well that’s interesting, because:

$ uname --kernel-release
5.0.4-200.fc29.x86_64

So I’m running kernel 5.0.4, but the kernel-headers package that I’m offered is for 5.0.9. I attempted to install the specific kernel header package by version:

yum install kernel-headers-5.0.4-200.fc29.x86_64
[...]
No match for argument: kernel-headers-5.0.4-200.fc29.x86_64

At this point, I had two viable options.

1. I could update the running kernel, since 5.0.10-200.fc29 was released and waiting for me.
2. I could go into Fedora’s build system, Koji, and pull out the specific kernel headers package that I needed to then install manually.

Choosing #2, however, would require me to uninstall the current 5.0.9 kernel headers, and anything that had it as a dependency. This includes things like binutils and gcc, among many others. I decided to update the system. A quick yum update and reboot later, and:

$ uname -or
5.0.10-200.fc29.x86_64 GNU/Linux

My only concern was that the headers that are in the official yum repo are 5.0.9; a minor version behind the new kernel:

rpm -q kernel-headers
kernel-headers-5.0.9-200.fc29.x86_64

Nevertheless, my fears were allayed with dkms:

$ dkms status
wireguard, 0.0.20190406, 5.0.10-200.fc29.x86_64, x86_64: installed

Previously, wireguard had only been added, but not successfully installed. I quickly tried to add a wireguard interface:

$ ip link add dev wg0 type wireguard
$ ip link show wg0
3: wg0: <POINTOPOINT,NOARP> mtu 1420 qdisc noop state DOWN mode DEFAULT group default qlen 1000 link/none 

Success!