quick-start.md

Quick Start

This guide assumes you have a Reaper-enabled cluster (see Installation).

Run a Command on the Host

The simplest way to run a command on the host is with a ReaperPod:

apiVersion: reaper.io/v1alpha1
kind: ReaperPod
metadata:
  name: my-task
spec:
  command: ["/bin/sh", "-c", "echo Hello from $(hostname) && uname -a"]

kubectl apply -f my-task.yaml
kubectl logs my-task
kubectl get reaperpods

With Volumes

apiVersion: reaper.io/v1alpha1
kind: ReaperPod
metadata:
  name: config-reader
spec:
  command: ["/bin/sh", "-c", "cat /config/settings.yaml"]
  volumes:
    - name: config
      mountPath: /config
      configMap: "my-config"
      readOnly: true

With Node Selector

apiVersion: reaper.io/v1alpha1
kind: ReaperPod
metadata:
  name: compute-task
spec:
  command: ["/bin/sh", "-c", "echo Running on $(hostname)"]
  nodeSelector:
    workload-type: compute

See ReaperPod CRD Reference for the full spec.

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Using Raw Pods

For use cases that need the full Kubernetes Pod API — interactive sessions, DaemonSets, Deployments, exec, etc. — you can use standard Pods with runtimeClassName: reaper-v2.

Note: The image field is required by Kubernetes but ignored by Reaper. Use a small image like busybox.

Run a Command

apiVersion: v1
kind: Pod
metadata:
  name: my-task
spec:
  runtimeClassName: reaper-v2
  restartPolicy: Never
  containers:
    - name: task
      image: busybox
      command: ["/bin/sh", "-c"]
      args: ["echo Hello from host && uname -a"]

kubectl apply -f my-task.yaml
kubectl logs my-task        # See output
kubectl get pod my-task     # Status: Completed

Interactive Shell

kubectl run -it debug --rm --image=busybox --restart=Never \
  --overrides='{"spec":{"runtimeClassName":"reaper-v2"}}' \
  -- /bin/bash

Exec into Running Containers

kubectl exec -it my-pod -- /bin/sh

Volumes

ConfigMaps, Secrets, hostPath, emptyDir, and projected volumes all work:

apiVersion: v1
kind: Pod
metadata:
  name: my-task
spec:
  runtimeClassName: reaper-v2
  restartPolicy: Never
  volumes:
    - name: config
      configMap:
        name: my-config
  containers:
    - name: task
      image: busybox
      command: ["/bin/sh", "-c", "cat /config/settings.yaml"]
      volumeMounts:
        - name: config
          mountPath: /config
          readOnly: true

See Pod Compatibility for the full list of supported and ignored fields.

What's Next

Reaper provides Custom Resource Definitions for higher-level workflows:

• ReaperPod — Simplified pod spec without container boilerplate
• ReaperOverlay — PVC-like overlay lifecycle management
• ReaperDaemonJob — Run jobs to completion on every matching node, with dependency ordering and shared overlays

See the CRD Reference for full documentation and the examples for runnable demos.