Cheat Sheet

Kubernetes

`kubectl get`

kubectl [-n <namespace>] get <obj> [-o wide],

where <obj> can be:

all returns all objects
pods
services
secrets

-o wide prints more details

`kubectl describe`

Describes the given object

kubectl describe <object-type> <name>

, where <object-type> is the type (e.g. pod, service, ...) and the <name> is the name

`kubectl logs <pod>`

kubectl logs [-f] [-p] <pod>

Returns the logs of the given pod

-f follows the log
-p also returns the logs of the previous instance

`kubectl rollout restart <deployments>`

Restarts the given deployments in a rolling fashion.

`kubectl create secret`

kubectl create secret generic <name> [--from-literal=<key>=<value>] [-o yaml] [--dry-run]

Creates a new secret with the <name> and the given key value. --from-literal=... can be supplied multiple times.

When adding -o yaml, the secrete is outputted as yaml. When appending --dry-run, the command is only simulated and doesn't have a lasting effect.

Secrets can be viewed by typing kubectl describe secrets <name>. The outputted values are stored in base64 and can be decoded with echo <base64 value> | base64 --decode

`kubectl delete secret <secret-name>`

Deletes a secret with the given name

`kubectl create configmap <name> [--from-file=<path>]`

Creates a new config map with the given name. If --from-file=<path> is appended, the value of the config map is read from the given file.

A config map can be retrieved with kubectl get configmap <name> -o yaml.

`kubectl port-forward <service/pod> [-n <namespace>] <external-port>:<internal-port>`

Forwards the <external-port> to the <internal-port> of the given pod or service

kubectl port-forward svc/argocd-server -n argocd 8443:443

`kubectl scale deployment <deployment-name> --replicas=<replica nr>`

Allows for modifying the number of replicas in a deployment.

`kubectl exec <pod name> -- <cmd>`

Executes a command in the given pod.

Kubernetes YAML File

apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app: order-deployment
    version: "1.0"
  name: order-deployment-name
spec:
  replicas: 1
  selector:
    matchLabels:
      app: order-pod
  strategy: {}
  template:
    metadata:
      labels:
        app: order-pod
    spec:
      containers:
      - name: order
        image: registry.localhost:5000/ccp2-order:1
        imagePullPolicy: Always
        ports:
        - containerPort: 8081
        resources: {}
---
apiVersion: v1
kind: Service
metadata:
  labels:
    app: order-service
  name: order-service-name
spec:
  type: ClusterIP
  ports:
  - port: <externalPort>
    protocol: TCP
    targetPort: <containerPort>
    name: http
  selector:
    app: order-pod
---
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: order-ingress-name
  labels:
    name: order-ingress
spec:
  rules:
  - host: order.160.85.253.189.nip.io
    http:
      paths:
      - pathType: Prefix
        path: "/"
        backend:
          service:
            name: order-service
            port:
              number: 80

K3D

`k3d cluster create`

To create a cluster:

k3d cluster create --config <path-to-config.yaml>

With kubectl cluster-info one can verify, if the cluster was correctly setup.

`k3d cluster delete`

This deletes a cluster

k3d cluster delete [--all]

buildpack

`pack build`

pack build <image-tag> --path <app-folder-path> --builder paketobuildpacks/builder-jammy-tiny

pack build ccp2-order:1 --path ./microservice-order --builder paketobuildpacks/builder-jammy-tiny

Helm

`helm repo add`

Adds a repository

helm repo add <name> <url>
helm repo add bitnami https://charts.bitnami.com/bitnami

`helm search [repo|hub] <what>`

Searches for a chart

`helm install [<name>] <chart-name> [--generate-name] [--set <key>=<value>]`

Installs the given chart.

To install a chart, either a name has to be given explicitly or --generate-name has to be set.--set <key>=<value> sets the value of .Values.<key> to the given value in the templates.

helm install bitnami/mysql --generate-name
helm install test-mysql bitnami/mysql

`helm show (chart|readme|values) <chart>`

Shows either the chart, readme file or values of the given chart.

helm show chart bitnami/mysql
helm show readme bitnami/mysql
helm show values bitnami/mysql

`helm list`

Lists the installed charts

`helm uinstall <chart>`

Uninstalls the given chart.

`helm lint <chart dir>`

Lints a helm chart

`helm template -f values.yaml <chart dir>`

Evaluates the templates in the given chart with the values in the values.yaml file.

Prometheus

container_cpu_usage_seconds_total{namespace="default"} Finds all container_cpu_usage_seconds_total object where namespace equals to default.
container_cpu_usage_seconds_total{namespace="default",name=""}[1m] Returns a vector of results in the given time period
rate(container_cpu_usage_seconds_total{namespace="default",name=""}[1m]) Calculates the rate of change (the first derivation) in the last 1 minute
sum(container_memory_usage_bytes{namespace="default"}) by(pod) This sums up the memory usage and groups it by the pod names. Additional columns can be specified in by (pod, namespace, ...)

The ~ means that the following expression is a regex. Thus field =~ "regex", filters if field matches the regex. On the other hand field !~ "regex", filters if the field does not match the regex.