📚 Lessons Learned from K3s Deployment Attempt on RunPod

1. Environment ≠ Real Server

  • RunPod “pods” are containerized environments, not real VMs.
  • Critical kernel features (mounting filesystems, /dev/kmsg, privileged container operations) are restricted.
  • Even with root access inside the pod, the host kernel limits remain.

🧠 Always verify if the environment allows privileged operations before deploying Kubernetes clusters.

2. K3s Needs More Than Just CPU and RAM

  • K3s is lightweight but still needs:

    • OverlayFS support (or fall back to --snapshotter=native)
    • Mount permissions (/var/lib/kubelet)
    • /dev/kmsg access for kubelet stability

  • If any of these are missing, kubelet will crash, and kubectl get nodes will fail.

🧠 Even for “small clusters,” Kubernetes expects server-like conditions.

3. Pod Security Kills Full Kubernetes

  • Security policies on container platforms (like RunPod) block:

    • Filesystem binds
    • Kernel modules
    • Device file operations

  • Thus, you cannot run full Kubernetes inside an unprivileged pod.

🧠 For Kubernetes control-plane, full host access is required — a cloud VM or Instant Cluster.

4. Good Debugging Habits Matter

  • Read k3s.log carefully.

  • Track fatal errors, not just the last log line.

  • Distinguish between:

    • Warnings you can ignore
    • Fatal errors that kill the system

  • Recognize signs like:

    • connection refused
    • operation not permitted
    • node not found

🧠 Debug in layers: overlayfs ➔ kubelet ➔ API server ➔ node registration.

5. Notes Are Not Wasted

  • Scripts to install:

    • Docker
    • kubectl
    • helm
    • K3s
    • NVIDIA container toolkit

  • Remain 100% valid on proper environments (e.g., VMs, bare metal, Instant Cluster).

🧠 Good documentation is still valuable even if one mission failed — it will serve the next.

📦 Key Tactical Insights

Problem Hit Tactical Insight Gained
OverlayFS not mountable Use --snapshotter=native always inside containers.
/dev/kmsg missing Use --kubelet-arg=feature-gates=KubeletInUserNamespace=true.
K3s exited during kubelet startup Need real disk bind-mounts, only possible on VMs or privileged clusters.
Cluster unreachable (kubectl failed) Always wait for kube-apiserver + kubelet to BOTH initialize.
Platform mismatch (pod vs server) Match environment to system requirements before building complex clusters.

🛡️ Final Reflection

“Victory is not measured by an easy battle won, but by the scars you wear into the next.”

Every error you faced trained your eyes. Every failure taught you to distinguish real server behavior from container illusions.

You are stronger now — and smarter.

This will never happen to you again.

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Note: These lessons were learned hands-on while attempting to deploy a full K3s Kubernetes cluster inside a non-privileged container on RunPod. They reflect real-world troubleshooting and hard-earned battle scars.