Kubernetes / K8s

Operations

ℹ️ There's also an official K8S cheatsheet here!

Set Default Namespace

kubectl config set-context --current --namespace=my-namespace

Get pods with label

kubectl get pods -l KEY=VALUE

Run command/shell on pod

-it is needed if interactive shell is required
-c <CONTAINER_NAME> to specify a container in multi-container pod

kubectl exec -it POD_NAME -- /bin/bash

# Target specific container in multi-container pod with '-c'
kubectl exec -it -c CONTAINER_NAME POD_NAME -- /bin/bash

Get Logs of container

kubectl logs POD_NAME

# Target specific container in multi-container pod with '-c'
kubectl logs -c CONTAINER_NAME POD_NAME

List all containers

In a specific pod...

kubectl get pods POD_NAME -o json | jq '.spec.containers[] | 
    {name, image} | join (", ")'

In all pods with a label...

kubectl get pods -l KEY=VALUE -o json | jq '.items[] | 
    .metadata.name as $POD_NAME | 
    .spec.containers[] | {"pod":$POD_NAME, name, image}'

Refresh Pods/Deployment

kubectl rollout restart deployment/my-app

Architecture

Services

NodePort

Exposes the service on each Node's IP at a static port ("NodePort")

Build

Patterns

See Kubernetes Patterns

Dry Run

Helpful to generate K8S YAML config files of ConfigMaps of raw file data as the YAML config for ConfigMap does not support file/path references.

This example creates a ConfigMap YAML config file by referencing the content of an actual file (config.ini) from the local system.

cat config.ini
[defualt]
config0 a
config1 b

kubectl create cm --dry-run=client test-cm --from-file=config.ini --output yaml

apiVersion: v1
data:
  config.ini: |
    [defualt]
    config0 a
    config1 b
kind: ConfigMap
metadata:
  creationTimestamp: null
  name: test-cm