add basic kubernetes commands
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206
virtualization/kubernetes/kubernetes_basics.md
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206
virtualization/kubernetes/kubernetes_basics.md
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---
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title: "Kubernetes Basics"
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tags: [ "virtualization", "kubernetes" ]
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requires: [ "Kubernetes Setup" ]
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---
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Install `kubectl`.
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> **NB:** Debian requires manual installation.[^kubedeb]
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[^kubedeb]: https://kubernetes.io/docs/tasks/tools/install-kubectl-linux/
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# Read
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1. Check the namespace: `kubectl get namespaces`
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1. Check the `${kube-system}` namespace: `kubectl get deployments.apps --namespace kube-system'
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1. Check host computers: `kubectl get nodes`
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1. Check pods: `kubectl get pods`
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```tree
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Namespaces
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├── Node_1: minikube
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│ ├── deployment_1: nginx
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│ │ ├── pod_1
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│ │ └── pod_2
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│ ├── deployment_2: database
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│ │ ├── pod_1
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│ │ ├── pod_2
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│ │ ├── pod_3
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│ │ └── pod_4
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│ ├── deployment_3: prometheus
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│ └── deployment_4: idk probably yaml
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└── Node_1: physical server
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├── deployment_1: nginx
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│ ├── pod_1
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│ └── pod_2
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├── deployment_2: database
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│ ├── pod_1
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│ ├── pod_2
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│ ├── pod_3
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│ └── pod_4
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├── deployment_3: prometheus
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└── deployment_4: Abandoned wiki
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```
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## More Information
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```bash
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$ kubectl get pod
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NAME READY STATUS RESTARTS AGE
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nginx-depl-68c944fcbc-2xbvq 1/1 Running 0 20m
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$ kubectl describe pod nginx-depl-68c944fcbc-2xbvq
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Name: nginx-depl-68c944fcbc-2xbvq
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Namespace: default
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Priority: 0
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Service Account: default
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Node: minikube/192.168.59.107
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Start Time: Fri, 29 Aug 2025 19:26:29 +0200
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Labels: app=nginx-depl
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pod-template-hash=68c944fcbc
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Annotations: <none>
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Status: Running
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IP: 10.244.0.3
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IPs:
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IP: 10.244.0.3
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Controlled By: ReplicaSet/nginx-depl-68c944fcbc
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Containers:
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nginx:
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Container ID: docker://aaa68e90ed9237dc0f98f9a21b0d7ddf3113188c62e72242d30cab4a43cbff98
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Image: nginx
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Image ID: docker-pullable://nginx@sha256:33e0bbc7ca9ecf108140af6288c7c9d1ecc77548cbfd3952fd8466a75edefe57
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Port: <none>
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Host Port: <none>
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State: Running
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Started: Fri, 29 Aug 2025 19:26:41 +0200
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Ready: True
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Restart Count: 0
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Environment: <none>
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Mounts:
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/var/run/secrets/kubernetes.io/serviceaccount from kube-api-access-9bgxx (ro)
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Conditions:
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Type Status
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PodReadyToStartContainers True
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Initialized True
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Ready True
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ContainersReady True
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PodScheduled True
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Volumes:
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kube-api-access-9bgxx:
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Type: Projected (a volume that contains injected data from multiple sources)
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TokenExpirationSeconds: 3607
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ConfigMapName: kube-root-ca.crt
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Optional: false
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DownwardAPI: true
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QoS Class: BestEffort
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Node-Selectors: <none>
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Tolerations: node.kubernetes.io/not-ready:NoExecute op=Exists for 300s
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node.kubernetes.io/unreachable:NoExecute op=Exists for 300s
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Events:
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Type Reason Age From Message
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---- ------ ---- ---- -------
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Normal Scheduled 24m default-scheduler Successfully assigned default/nginx-depl-68c944fcbc-2xbvq to minikube
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Normal Pulling 24m kubelet Pulling image "nginx"
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Normal Pulled 24m kubelet Successfully pulled image "nginx" in 11.204s (11.204s including waiting). Image size: 192385800 bytes.
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Normal Created 24m kubelet Created container: nginx
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Normal Started 24m kubelet Started container nginx
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```
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Pod copies are called a 'replicaset'.
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# Create
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Create a 'deployment' of `nginx`.
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```sh
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name="nginx-depl"
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kubectl create deployment ${name} --image=nginx
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kubectl get deployments
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```
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The command did not specify a namespace, so `default` is used.
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# Update
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Update a deployment, with `$EDITOR`.
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```sh
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kubectl edit deployments.apps ${name}
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```
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This gives us far too much information:
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```yaml
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apiVersion: apps/v1
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kind: Deployment
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metadata:
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annotations:
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deployment.kubernetes.io/revision: "1"
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[ ... ]
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creationTimestamp: "2025-08-29T18:13:45Z"
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generation: 3
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labels:
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app: nginx-depl
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name: nginx-depl
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namespace: default
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resourceVersion: "17696"
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uid: 8dec2925-5c34-4635-b82c-ba601cb3bef5
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spec:
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progressDeadlineSeconds: 600
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replicas: 2
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revisionHistoryLimit: 10
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selector:
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matchLabels:
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app: nginx-depl
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[ ... ]
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observedGeneration: 3
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readyReplicas: 2
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replicas: 2
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updatedReplicas: 2
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```
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Pull out the information, without an `$EDITOR`:
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```sh
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file="webstuff"
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kubectl get deployment ${name} -o yaml > ${webstuff}.yaml
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```
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## Enter the Pod
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```bash
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$ kubectl get pods
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NAME READY STATUS RESTARTS AGE
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nginx-depl-68c944fcbc-2xbvq 1/1 Running 0 31m
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$ pod='nginx-depl-68c944fcbc-2xbvq'
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$ kubectl exec -it ${pod} -- bash
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root@nginx-depl-68c944fcbc-2xbvq:/# ls
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bin dev docker-entrypoint.sh home lib64 mnt proc run srv tmp var
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boot docker-entrypoint.d etc lib media opt root sbin sys usr
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root@nginx-depl-68c944fcbc-2xbvq:/#
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exit
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```
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# Delete
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Delete a deployment, and watch it leave:
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```sh
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name=nginx-depl
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kubectl delete deployments.apps nginx-depl && kubectl get deployments.apps
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kubectl get deployments.apps
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```
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