WSL: Mount linux folder in kubernetes

[benzman81]

Hi,
I couldnt find any answer to this. How can I mount a folder in WSL linux using kubernetes hostPath? If I use the linux path /home/myuser/foo then an empty folder with this path is created in \\wsl$\rancher-desktop but not the linux path from WSL is mounted. I know that I have acces to /mnt/c/ for my windows system, but this doesnt help here. Any hints?
Regards,
Markus

[adamkpickering]

My understanding of the issue is below. @mook-as if you have anything to add, it would help!

There are three entities we need to be aware of:

1. the host machine
2. the RD VM, which is where k8s, dockerd and/or containerd run
3. the user VM that you are trying to mount a directory from

As you have noticed, both the RD VM and the user VM have access to the C drive on the host machine via /mnt/c/. I'm not aware of any other mounts, but I could be missing something. A simple solution, then, could be working in the /mnt/c directory. That way, any files created in that folder in the user VM would get passed through to the host machine, and then to the RD VM. So you could use the same path for your hostPath config as you are working with in the user VM.

I don't have a better answer than that. You could also try messing around with symlinks to /mnt/c in the user VM if you want your stuff in a different directory. Does that answer your question?

[mook-as]

The relevant difference is that there's actually one VM, but two containers (the RD one, and the other distro) running on top of it. (RD then runs nested containers via dockerd/containerd.)

/mnt/wsl is a shard mount point across all distributions; that is, it's a mount point that is mounted into each distribution. This means that you can achieve host path mounting from a different distribution by:

1. From the target distro, bind mount /home/myuser/foo into /mnt/wsl/foo.
2. In your hostPath configuration, tell it to use /mnt/wsl/foo.

This is in fact what we do in nerdctl-stub to handle volume mounts when running nerdctl from a WSL distribution. We also do this (backwards) to expose docker.sock to the other distributions when using dockerd.

(Note that the mount prefix is configurable per distribution.)

[benzman81]

Thanks. Now I have a better understanding of how it work and what I can do to mount my folder.