[FEATURE] Configurable kernel parameters in node containers

[ehaymore]

Scope of your request

k3d is awesome! I have a need to modify namespaced kernel parameters (e.g. kernel.sem) in the k3s cluster node containers that k3d creates. These parameters can't be modified from inside a running container so they must be specified at the time it's created.

Describe the solution you'd like

"docker run" provides a --sysctl option that provides this functionality when creating containers manually. It would be nice to have a k3d configuration option which allows modifications to kernel parameters to be specified and that can pass this information to the node container creation when creating the cluster.

[iwilltry42]

Hi @ehaymore , thanks for opening this issue!
Out of curiosity, can you tell a bit more about your use case that requires you to modify kernel parameters?

[ehaymore]

Sure - I'm running a distributed application with a lot of complex interacting pieces and it's pretty demanding in its use of shared memory and semaphores. (I don't have any ability to try to reduce those needs.) When run with the standard kernel defaults for those parameters in CentOS 7, which is what the k3s node containers get, the app crashes and burns because it reaches those limits. The pods within k3s inherit the parameter values of the environment they're run in, so if I can get them set properly in the node containers, I'll be OK.

I know there's some ability in Kubernetes to modify kernel parameters for pods using a securityContext which could have been an option, but because I have to run my pods with hostIPC within each k3s node (but not across nodes), I'm not allowed to change the parameters via Kubernetes - they have to be already set within the node container.