CODEWITHSUNDEEP
dockerkernel-module
Karai17
Karai17

Reputation: 943

Is it possible to use a kernel module built from within Docker?

I have a custom kernel module I need to build for a specific piece of hardware. I want to automate setting up my system so I have been containerizing several applications. One of the things I need is this kernel module. Assuming the kernel headers et al in the Docker container and the kernel on the host are for the exact same version, is it possible to have my whole build process containerized and allow the host to use that module?

Upvotes: 2

Views: 4092

Answers (1)

David Maze
David Maze

Reputation: 159242

Many tasks that involve controlling the host system are best run directly on the host, and I would avoid Docker here.

At a insmod(8) level, Docker containers generally run with a restricted set of permissions and can’t make extremely invasive changes like this over the host. There’s probably a docker run --cap-add option that would theoretically make it possible, but a significant design statement of Docker is that container processes aren’t supposed to be able to impact other containers or the host like this.

At an even broader Linux level, the build version of custom kernel modules has to match the host’s kernel exactly. This means, if you update the host kernel (for a routine security update for example) you have to also rebuild and reinstall any custom modules. Mainstream Linux distributions have support for this, but if you’ve boxed away management of this into a container, you have to remember how to rebuild the container with the newer kernel headers and make sure it doesn’t get restarted until you reboot the host. That can be tricky.

At a Docker level, you’re in effect building an image that can only be used on one very specific system. Usually the concept is to build an image that can be reused in multiple contexts; you want to be able to push the image to a registry and run it on another system with minimal configuration. It’s hard to do this if an image is tied to an extremely specific kernel version or other host-level dependency.

Upvotes: 4

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