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kubernetes-commands.md

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Kubernetes - Commands kubernetes

Kubectl?

  • "Kubectl is a command-line interface that lets you run commands on Kubernetes clusters." This is how we will be able to perform various operations on our cluster.

  • Kubectl depends on a kubeconfig. This is a configuration file for access to one or more clusters, to know which cluster is configured our Kubectl command, we can use:

    Kubectl config current-context

  • Or if we want to change clusters in our config, we can use:

    Kubectl config use-context

CLIENT CONFIGURATION

  • Setup autocomplete in bash; bash-completion package should be installed first

source <(kubectl completion bash)

  • View Kubernetes config

kubectl config view

  • View specific config items by json path

kubectl config view -o jsonpath='{.users[?(@.name == "k8s")].user.password}'

  • Set credentials for foo.kuberntes.com

kubectl config set-credentials kubeuser/foo.kubernetes.com --username=kubeuser --password=kubepassword

VIEWING, FINDING RESOURCES

  • List all services in the namespace

kubectl get services

  • List all pods in all namespaces in wide format

kubectl get pods -o wide --all-namespaces

  • List all pods in json (or yaml) format

kubectl get pods -o json

  • Describe resource details (node, pod, svc)

kubectl describe nodes my-node

  • List services sorted by name

kubectl get services --sort-by=.metadata.name

  • List pods sorted by restart count

kubectl get pods --sort-by='.status.containerStatuses[0].restartCount'

  • Rolling update pods for frontend-v1

kubectl rolling-update frontend-v1 -f frontend-v2.json

  • Scale a replicaset named 'foo' to 3

kubectl scale --replicas=3 rs/foo

  • Scale a resource specified in "foo.yaml" to 3

kubectl scale --replicas=3 -f foo.yaml

  • Execute a command in every pod / replica

for i in 0 1; do kubectl exec foo-$i -- sh -c 'echo $(hostname) > /usr/share/nginx/html/index.html'; done

MANAGE RESOURCES

  • Create one or more resources from your file or folder.

kubectl create -f FILE

  • Applies a configuration change to a resource from your file.

kubectl apply -f FILE

  • Deletes one or more Kubernetes resources from a configuration file or directly from resource names.
  • e.g. Kubectl delete my_pod (destroy the pod on the cluster named my_pod)

kubectl delete (-f FILE | TYPE [PREFIX_NAME | NAME])

  • Lets you expose a local port to the port of a POD that is running on the Kubernetes cluster. Useful to debug.
    • e.g. Kubectl port-forward my_pod 80:3000 (exposes the port 3000 of the pod my_pod on our local port 80)

kubectl port-forward POD [LOCAL_PORT:]REMOTE_PORT

  • Run a resource in the Kubernetes cluster.
    • e.g.kKubectl run -i --tty busybox --image=busybox -- sh
    • -> Run a pod as an interactive shell

kubectl run NAME --image=image [--env=”key=value”] [--port=port] [--replicas=replicas]

  • Get documentation for pod or service

kubectl explain pods,svc

  • Create resource(s) like pods, services or daemonsets

kubectl create -f ./my-manifest.yaml

  • Apply a configuration to a resource

kubectl apply -f ./my-manifest.yaml

  • Start a single instance of Nginx

kubectl run nginx --image=nginx

  • Create a secret with several keys
cat <<EOF | kubectl create -f -
apiVersion: v1
kind: Secret
metadata:
 name: mysecret
type: Opaque
data:
 password: $(echo "s33msi4" | base64)
 username: $(echo "jane"| base64)
EOF
  • Delete a resource

kubectl delete -f ./my-manifest.yaml

MONITORING & LOGGING

  • Kubectl monitoring commands

    Kubectl get pods

This command lists pods on the Kubernetes cluster. This command works for all types of Kubernetes resources: pods, services, deployments, cronjobs, events, ingresses, etc. We can also add parameters:

  • --all-namespaces: List all resources of all namespaces.

  • -o wide: List all resources with more details.

    Kubectl describe pod

The describe command gives a verbose display of the pod unlike the get and basic display. This allows having the events, useful when a pod does not start.

e.g. Kubectl describe pods my-pod.

kubectl logs [-f] POD [-c CONTAINER]

This command displays the logs of your POD. We can add the -c container option when we want to display the logs of a multi-container pod. The -f command displays the output of the logs continuously (stream).

Example: Kubectl logs -f my_pod -c my_app

-> Stream the logs of the container my_app on the my_pod pod.

kubectl top pod POD_NAME --containers

Displays the metrics for a given pod and its containers within a Kubernetes cluster.

  • Deploy Heapster from Github repository

kubectl create -f deploy/kube-config/standalone/

  • Show metrics for nodes

kubectl top node

  • Show metrics for pods

kubectl top pod

  • Show metrics for a given pod and its containers

kubectl top pod pod_name --containers

  • Dump pod logs (stdout)

kubectl logs pod_name

  • Stream pod container logs (stdout, multi-container case)

kubectl logs -f pod_name -c my-container