# Kubectl

The Kubernetes command-line tool, Kubectl allows you to run commands against Kubernetes clusters. You can use kubectl to deploy applications, inspect and manage cluster resources, and view logs.

Get configured contexts: kubectl config get-contexts
Switch context: kubectl config use-context <NAME>
Get pods: kubectl get pods -n <NAMESPACE>
Kill pod: kubectl delete pod -n <NAMESPACE> <POD_NAME> --force --grace-period=0
Get more details (for example of a pod): kubectl get pod -n <NAMESPACE> <POD_NAME> -o wide
Describe pod: kubectl describe pod -n <NAMESPACE> <POD_NAME>
Get persistent volumes: kubectl get pvc
Get pods filtered on label: kubectl get pods --all-namespaces -l app=nginx
Open container shell: kubectl exec -n <NAMESPACE> --stdin --tty <POD_NAME> -- /bin/sh Sort by (for example pod names): kubectl get pods --all-namespaces --sort-by=.metadata.name
Sort by (for example persistent volumes): kubectl get pods --all-namespaces --sort-by=.spec.capacity.storage
Sort by (for example events): kubectl get events --sort-by=.metadata.creationTimestamp
Get all supported resource types: kubectl api-resources

Create file and apply (secret example) Because kubectl create can only be run once, you can output the secret as YAML and pipe this to kubectl apply. kubectl create secret generic <SECRET_NAME> -n <NAMESPACE> --from-literal=<USERNAME_VARIABLE>=<USERNAME> --from-literal=<PASSWORD_VARIABLE>=<PASSWORD> --dry-run=client -o yaml | kubectl apply -f -

-> More in the Cheatsheet

Get all namespaces: kubectl get namespace Create namespace: kubectl create namespace <NAMESPACE_NAME>

Create namespace (example YAML):

apiVersion: v1
kind: Namespace
metadata:
  name: <NAMESPACE>

-> Apply namespace: kubectl apply -f .\namespace.yml

deployment.yaml:

apiVersion: apps/v1
kind: Deployment
metadata:
 name: <DEPLOYMENT_NAME>
 labels:
   app: nginx
spec:
 replicas: 3
 selector:
   matchLabels:
     app: nginx
 template:
   metadata:
     labels:
       app: nginx
   spec:
     containers:
     - name: nginx
       image: nginx:1.14.2
       ports:
       - containerPort: 80

-> Apply deployment: kubectl apply -f .\deployment.yml -n <NAMESPACE>

service.yaml:

apiVersion: v1
kind: Service
metadata:
 name: <SERVICE_NAME>
spec:
 type: ClusterIP
 selector:
   app: nginx
 ports:
 # By default and for convenience, the `targetPort` is set to the same value as the `port` field.
 - port: 80
   targetPort: 80
   # Optional field
   # By default and for convenience, the Kubernetes control plane will allocate a port from a range (default: 30000-32767)
   # nodePort: 30011

-> Apply service: kubectl apply -f .\service.yml -n <NAMESPACE>

ingress.yaml:

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
 name: <INGRESS_NAME>
spec:
 rules:
 - host: nginx.apps.yourdomain.ch
 http:
   paths:
   - path: /
     pathType: Prefix
     backend:
       service:
         name: <SERVICE_NAME>
         port:
           number: 80

-> Apply ingress: kubectl apply -f .\ingress.yaml -n <NAMESPACE>

Add Kubectl autocompletion to load on each PowerShell session:

kubectl completion powershell >> $PROFILE

JSONPATH kubectl get pods -n <NAMESPACE> -o jsonpath="{range .items[*]}{.metadata.name}{'\t'}{.spec.containers[*].resources}{'\n'}{end}"

Custom Columns kubectl get pods -n grafana --output=custom-columns="POD:.metadata.name,CONTAINERS:.spec.containers[*].name,REQUESTS:.spec.containers[*].resources.requests,LIMITS:.spec.containers[*].resources.limits"