Kubernetes¶

Context and Namespaces¶

Show current/all context¶

$ kubectl config get-contexts
CURRENT   NAME             CLUSTER          AUTHINFO                        NAMESPACE
          dev              dev_cluster      dev_user                        default
          minikube         minikube         minikube                        default
*         prod             prod_cluster     production_user                 default
          staging          staging_cluster  staging_user                    default

Switch context¶

$ kubectl config use-context <CONTEXT>

Switch namespace¶

$ kubectl config set-context --current --namespace <NAMESPACE>

CronJob¶

Run CronJob immediate¶

kubectl create job test --from=cronjobs/cronjob123

Events¶

Get latest events¶

$ kubectl get events --sort-by='{.lastTimestamp}'

Colorized event watching¶

$ kubectl get events --all-namespaces --watch \
    -o 'go-template={{.lastTimestamp}} _ {{.involvedObject.kind}} _ {{.message}} _ ({{.involvedObject.name}}){{"\n"}}' \
    | awk -F_ \
    -v black=$(tput setaf 0) \
    -v red=$(tput setaf 1) \
    -v green=$(tput setaf 2) \
    -v yellow=$(tput setaf 3) \
    -v blue=$(tput setaf 4) \
    -v magenta=$(tput setaf 5) \
    -v cyan=$(tput setaf 6) \
    -v white=$(tput setaf 7) \
    '{
        $1=blue $1
        $2=green $2
        $3=white $3
    }
    1'

Secrets¶

Show secret encoded¶

$ kubectl get secret -o yaml the-secret-we-want-to-see | yq '.data |= map_values(. | @base64d)'

Image Pull Secrets¶

Add default Image Pull Secret to Service-Account¶

$ kubectl patch serviceaccount <SERVICE_ACCOUNT_NAME> -p '{"imagePullSecrets": [{"name": "<SECRET_NAME"}]}'

Nginx Ingress¶

Domain Redirect¶

The redirect code 307 preserves the sending of payload on a POST request.

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  annotations:
    nginx.ingress.kubernetes.io/permanent-redirect: https://target.domain.de$request_uri
    nginx.ingress.kubernetes.io/permanent-redirect-code: '307'
  name: keycloak-redirect
spec:
  ingressClassName: nginx
  rules:
    - host: domain.which.should.be.redirect.de
  tls:
    - hosts:
        - domain.which.should.be.redirect.de
      secretName: some-secret-tls

Debugging¶

$ kubectl run --rm -it debugging --image alpine

$ kubectl run --rm -ti debugging --image alpine --overrides='
{
    "spec": {
        "containers": [
            {
                "stdin": true,
                "tty": true,
                "args": [ "/bin/sh" ],
                "name": "debugging",
                "image": "alpine",
                "volumeMounts": [
                    {
                        "mountPath": "/data",
                        "name": "data"
                    }
                ]
            }
        ],
        "volumes": [
            {
                "name": "data",
                "emptyDir": {}
            }
        ]
    }
}'

JSON-Path Queries¶

Show special Env-Value¶

Replace <ENV_NAME> with the real env name.

kubectl get pods -o=jsonpath='{range .items[*]}{.metadata.name}{"\t"}{.spec.containers[0].env[?(@.name=="<ENV_NAME>")].value}{"\n"}{end}

Versioning¶

Fetching resource in specific version¶

kubectl get <RESOURCE_KIND>.<RESOURCE_VERSION>.<RESOURCE_GROUP>

Example:

kubectl get alertmanagerconfig.v1alpha1.monitoring.coreos.com
kubectl get alertmanagerconfig.v1beta1.monitoring.coreos.com