Kubernetes snippets

Spec Explorer

• kube-spec.dev: A handy tool for exploring Kubernetes resource specifications.
  • Link: https://kubespec.dev

Running a One-Time Job from a CronJob

• To execute a job based on an existing CronJob, use the following command:

  kubectl create job --from=cronjob/<cronjob-name> <job-name> -n <namespace-name>
  

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  • Source: https://stackoverflow.com/a/50041304

Spawning a Curl Container for Debugging

• To quickly spin up a curl container with specific security and resource constraints, use:

  kubectl run debug-curl \
    --image=curlimages/curl \
    --overrides='{
      "apiVersion": "v1",
      "spec": {
        "securityContext": {
          "runAsNonRoot": true,
          "runAsUser": 1000,
          "runAsGroup": 1000
        },
        "containers": [
          {
            "name": "debug-curl",
            "image": "curlimages/curl",
            "resources": {
              "requests": {
                "cpu": "100m",
                "memory": "128Mi"
              },
              "limits": {
                "cpu": "200m",
                "memory": "256Mi"
              }
            },
            "command": ["/bin/sh", "-c", "sleep infinity"]
          }
        ]
      }
    }'
  

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  • This command creates a debug-curl pod with a non-root user context and resource requests/limits.
  • Connect to the shell using:

  kubectl exec pod/debug-curl sh
  

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  • Delete container using

  kubectl delete pod/debug-curl
  

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Getting Kubernetes Events

• To view Kubernetes events sorted by creation timestamp, use:

  kubectl get events --sort-by='.metadata.creationTimestamp' -o wide | less
  

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  • The less command enables easy scrolling and searching through the event list.

Explaining Specific Kubernetes Fields

• To get detailed information about a specific field in a Kubernetes resource specification, use kubectl explain:

  kubectl explain "postgrescluster.spec.backups.pgbackrest.repos.s3" # sample field
  

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  • Replace "postgrescluster.spec.backups.pgbackrest.repos.s3" with the desired field path. This is very usefull for understanding the expected structure and values of kubernetes resources.