Kubeconfig mount path doesn't match container user (appuser vs root)

[samhanoun]

Hey,

I was trying to get the Kubernetes MCP server working with Docker MCP Gateway on Windows, and ran into a permission issue that took me a while to track down.

What's happening

The kubeconfig file gets mounted to /root/.kube/config, but the container actually runs as appuser (uid 1001), not root. So when the server tries to read the config, it gets "Permission denied".

Quick proof

# The container runs as appuser
$ docker run --rm mcp/kubernetes id
uid=1001(appuser) gid=1001(appuser)

# Mounting to /root fails
$ docker run --rm -v "$HOME/.kube/config:/root/.kube/config" mcp/kubernetes cat /root/.kube/config
cat: /root/.kube/config: Permission denied

# But mounting to /home/appuser works perfectly
$ docker run --rm -v "$HOME/.kube/config:/home/appuser/.kube/config" mcp/kubernetes kubectl get nodes
NAME     STATUS   ROLES                       AGE   VERSION
k3s-01   Ready    <none>                      9d    v1.26.10+k3s2
k3s-02   Ready    <none>                      9d    v1.26.10+k3s2
... (all nodes work fine)

My setup

• Windows 11
• Docker Desktop 29.1.2
• Docker MCP v0.28.0
• K3S cluster (5 nodes, works great with local kubectl)

Update

After investigating further, I found that the correct mount path (/home/appuser/.kube/config) is already documented in ADVANCED_README.md. The issue is actually in Docker MCP Gateway, which appears to be mounting to the wrong path.

This issue should be reported to the Docker MCP Gateway team instead.

[samhanoun]

Actually, after digging more into this - I found that you already document the correct path in ADVANCED_README.md:

-v ~/.kube/config:/home/appuser/.kube/config

So this is working as designed! The issue is actually in Docker MCP Gateway - it's apparently mounting to /root/.kube/config instead of /home/appuser/.kube/config.

I'll close this issue and report it to the Docker MCP team instead. Sorry for the noise! 🙏

[Flux159]

Hi, thanks for investigating. There's been a few issues that have been reported here around the docker gateway / registry implementation. #215, #225

I don't know the difference between docker's mcp-gateway implementation and their registry, but the registry may support a kubernetes.config_path argument. Here's a PR that has that in the registry repo: docker/mcp-registry#278 (not sure if this is available as an option in the gateway though).

For reference, I have commented in the docker/mcp-registry repo offering to help update their implementation, but have not received any response: docker/mcp-registry#275