Kubernetes| Getting started

by Ralph Docker, Kubernetes, Virtual Machine, Virtualbox

Inhaltsverzeichnis

Readings

TL;DR

Helm (Documentation): Using Helm

choco install kubernetes-helm
helm
helm repo add stable https://charts.helm.sh/stable
helm search repo stable
helm repo update
helm install stable/mysql --generate-name
helm install stable/mysql --generate-name
helm ls
helm status mysql-1609772389
helm search hub wordpress
helm repo add brigade https://brigadecore.github.io/charts
helm repo ls
helm search repo brigade

Customizing the Chart Before Installing

Helm: Concepts

Three Big Concepts

ChartHelm package. It contains all of the resource definitions necessary to run an application, tool, or service inside of a Kubernetes cluster.
RepositoryPlace where charts can be collected and shared.
ReleaseInstance of a chart running in a Kubernetes cluster.
One chart can often be installed many times into the same cluster. And each time it is installed, a new release is created.
Consider a MySQL chart. If you want two databases running in your cluster, you can install that chart twice. Each one will have its own release, which will in turn have its own release name.

Helm: Creating Charts

helm create chartname
helm package chartname
helm install mychart
helm install mychart mychart/ --values mychart/values.yaml
helm ls
helm delete generated-deployment-name
helm package mychart
helm install mychart-0.1.0.tgz
helm install release-name mychart

Helm: CLI

Common actions for Helm:

- helm search:    search for charts
- helm pull:      download a chart to your local directory to view
- helm install:   upload the chart to Kubernetes
- helm list:      list releases of charts

Environment variables:

| Name                               | Description                                                                       |
|------------------------------------|-----------------------------------------------------------------------------------|
| $HELM_CACHE_HOME                   | set an alternative location for storing cached files.                             |
| $HELM_CONFIG_HOME                  | set an alternative location for storing Helm configuration.                       |
| $HELM_DATA_HOME                    | set an alternative location for storing Helm data.                                |
| $HELM_DEBUG                        | indicate whether or not Helm is running in Debug mode                             |
| $HELM_DRIVER                       | set the backend storage driver. Values are: configmap, secret, memory, postgres   |
| $HELM_DRIVER_SQL_CONNECTION_STRING | set the connection string the SQL storage driver should use.                      |
| $HELM_MAX_HISTORY                  | set the maximum number of helm release history.                                   |
| $HELM_NAMESPACE                    | set the namespace used for the helm operations.                                   |
| $HELM_NO_PLUGINS                   | disable plugins. Set HELM_NO_PLUGINS=1 to disable plugins.                        |
| $HELM_PLUGINS                      | set the path to the plugins directory                                             |
| $HELM_REGISTRY_CONFIG              | set the path to the registry config file.                                         |
| $HELM_REPOSITORY_CACHE             | set the path to the repository cache directory                                    |
| $HELM_REPOSITORY_CONFIG            | set the path to the repositories file.                                            |
| $KUBECONFIG                        | set an alternative Kubernetes configuration file (default "~/.kube/config")       |
| $HELM_KUBEAPISERVER                | set the Kubernetes API Server Endpoint for authentication                         |
| $HELM_KUBEASGROUPS                 | set the Groups to use for impersonation using a comma-separated list.             |
| $HELM_KUBEASUSER                   | set the Username to impersonate for the operation.                                |
| $HELM_KUBECONTEXT                  | set the name of the kubeconfig context.                                           |
| $HELM_KUBETOKEN                    | set the Bearer KubeToken used for authentication.                                 |

Helm stores cache, configuration, and data based on the following configuration order:

– If a HELM_*_HOME environment variable is set, it will be used
– Otherwise, on systems supporting the XDG base directory specification, the XDG variables will be used
– When no other location is set a default location will be used based on the operating system

By default, the default directories depend on the Operating System. The defaults are listed below:

| OS      | Cache Path                | Configuration Path             | Data Path
|---------|---------------------------|--------------------------------|-------------------------|
| Linux   | $HOME/.cache/helm         | $HOME/.config/helm             | $HOME/.local/share/helm
| macOS   | $HOME/Library/Caches/helm | $HOME/Library/Preferences/helm | $HOME/Library/helm
| Windows |

Available Commands:

  completion  generate autocompletions script for the specified shell
  create      create a new chart with the given name
  dependency  manage a chart's dependencies
  env         helm client environment information
  get         download extended information of a named release
  help        Help about any command
  history     fetch release history
  install     install a chart
  lint        examine a chart for possible issues
  list        list releases
  package     package a chart directory into a chart archive
  plugin      install, list, or uninstall Helm plugins
  pull        download chart from repository and unpack in local directory
  repo        add, list, remove, update, and index chart repositories
  rollback    roll back a release to a previous revision
  search      search for a keyword in charts
  show        show information of a chart
  status      display the status of the named release
  template    locally render templates
  test        run tests for a release
  uninstall   uninstall a release
  upgrade     upgrade a release
  verify      verify that a chart at the given path has been signed and is valid
  version     print the client version information

Flags

      --debug                       enable verbose output
  -h, --help                        help for helm
      --kube-apiserver string       the address and the port for Kubernetes API server
      --kube-as-group stringArray   Group to impersonate for the operation, 
                                    flag can be repeated to specify multiple groups.
      --kube-as-user string         Username to impersonate for the operation
      --kube-context string         name of the kubeconfig context to use
      --kube-token string           bearer token used for authentication
      --kubeconfig string           path to the kubeconfig file
  -n, --namespace string            namespace scope for this request
      --registry-config string      path to the registry config file 
                                    (<User>\AppData\Roaming\helm\registry.json)
      --repository-cache string     path to file containing cached repository indexes
                                    (<User>\AppData\Local\Temp\helm\repository)
      --repository-config string    path to file containing repository names and URLs
                                   (<User>\AppData\Roaming\helm\repositories.yaml)
 
Use "helm [command] --help" for more information about a command.

General Information

Minikube

Installation

https://minikube.sigs.k8s.io/docs/start/

Start Cluster

minikube start
* minikube v1.16.0 auf Microsoft Windows 10 Pro 10.0.19042 Build 19042
* Automatically selected the docker driver
* Starting control plane node minikube in cluster minikube
* Pulling base image ...
* Downloading Kubernetes v1.20.0 preload ...
    > preloaded-images-k8s-v8-v1....: 491.00 MiB / 491.00 MiB  100.00% 24.50 Mi
* Creating docker container (CPUs=2, Memory=8100MB) ...
E1225 11:29:49.056358   11564 kic.go:241] icacls failed applying permissions - err - [
1 Dateien erfolgreich verarbeitet, bei 0 Dateien ist ein Verarbeitungsfehler aufgetreten.]
* Vorbereiten von Kubernetes v1.20.0 auf Docker 20.10.0...
  - Generating certificates and keys ...
  - Booting up control plane ...
  - Configuring RBAC rules ...
* Verifying Kubernetes components...
* Enabled addons: storage-provisioner, default-storageclass
* Done! kubectl is now configured to use "minikube" cluster and "default" namespace by default
kubectl get po -A
minikube kubectl -- get po -A
minikube dashboard
kubectl create deployment hello-minikube --image=k8s.gcr.io/echoserver:1.4
kubectl expose deployment hello-minikube --type=NodePort --port=8080

kubectl get services hello-minikube
minikube service hello-minikube

Alternatively, use kubectl to forward the port:

kubectl port-forward service/hello-minikube 7080:8080

Kubernetes Basics Module

Reference

Kubernetes : production-grade, open-source platform that orchestrates the placement (scheduling) and execution of application containers within and across computer clusters.

Deployment: responsible for creating and updating instances of your application

Pod: group of one or more application containers (such as Docker) and includes shared storage (volumes), IP address and information about how to run them.

Node: a worker machine in Kubernetes and may be either a virtual or a physical machine, depending on the cluster. Multiple Pods can run on one Node.

Kubernetes Service: abstraction layer which defines a logical set of Pods and enables external traffic exposure, load balancing and service discovery for those Pods.

Scaling is accomplished by changing the number of replicas in a Deployment

Tutorial

1. Create a Kubernetes cluster

minikube version
minikube start
kubectl cluster-info
Kubernetes control plane is running at https://127.0.0.1:49153
KubeDNS is running at https://127.0.0.1:49153/api/v1/namespaces/kube-system/services/kube-dns:dns/proxy

2. Deploy an App

kubectl get node
NAME       STATUS   ROLES                  AGE     VERSION
minikube   Ready    control-plane,master   5d22h   v1.20.0
kubectl create deployment kubernetes-bootcamp --image=gcr.io/google-samples/kubernetes-bootcamp:v1
deployment.apps/kubernetes-bootcamp created
kubectl get deployments
NAME                  READY   UP-TO-DATE   AVAILABLE   AGE
kubernetes-bootcamp   1/1     1            1           52s
kubectl proxy
Starting to serve on 127.0.0.1:8001
curl http://localhost:8001/version
{
  "major": "1",
  "minor": "20",
  "gitVersion": "v1.20.0",
  "gitCommit": "af46c47ce925f4c4ad5cc8d1fca46c7b77d13b38",
  "gitTreeState": "clean",
  "buildDate": "2020-12-08T17:51:19Z",
  "goVersion": "go1.15.5",
  "compiler": "gc",
  "platform": "linux/amd64"
}
kubectl get pods
NAME                                   READY   STATUS    RESTARTS   AGE
hello-minikube-6ddfcc9757-kpl5f        1/1     Running   1          5d22h
kubernetes-bootcamp-57978f5f5d-ccr6p   1/1     Running   0          6m25s
k
ubectl get pods -o go-template --template '{{range .items}}{{.metadata.name}}{{end}}'

3. Explore your app

kubectl get pods

> kubectl describe pods
> kubectl get pods -o go-template --template '{{range .items}}{{.metadata.name}}{{end}}'
kubernetes-bootcamp-57978f5f5d-z8vsm
> $PODNAME=kubectl get pods -o go-template --template '{{range .items}}{{.metadata.name}}{{end}}
> Invoke-WebRequest http://localhost:8001/api/v1/namespaces/default/pods/$PODNAME
StatusCode        : 200
StatusDescription : OK
Content           : {
                      "kind": "Pod",
                      "apiVersion": "v1",
                      "metadata": {
                        "name": "kubernetes-bootcamp-57978f5f5d-z8vsm",
                        "generateName": "kubernetes-bootcamp-57978f5f5d-",
                        "namespace": "default",
                        "uid…
RawContent        : HTTP/1.1 200 OK
                    Cache-Control: no-cache, private
                    Date: Thu, 31 Dec 2020 10:07:12 GMT
                    X-Kubernetes-Pf-Flowschema-Uid: be79abd4-3f87-4ca2-80be-2b83f4c48148
                    X-Kubernetes-Pf-Prioritylevel-Uid: 3c0f88d…
Headers           : {[Cache-Control, System.String[]], [Date, System.String[]], [X-Kubernetes-Pf-Flowschema-Uid, System.String[]], [X-Kubernetes-Pf-Prioritylevel-Uid, System.String[]]…}
Images            : {}
InputFields       : {}
Links             : {}
RawContentLength  : 5593
RelationLink      : {}
> kubectl logs $PODNAME
Kubernetes Bootcamp App Started At: 2020-12-31T09:09:43.763Z | Running On:  kubernetes-bootcamp-57978f5f5d-z8vsm
> kubectl exec $PODNAME env
kubectl exec [POD] [COMMAND] is DEPRECATED and will be removed in a future version. Use kubectl exec [POD] -- [COMMAND] instead.
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
HOSTNAME=kubernetes-bootcamp-57978f5f5d-z8vsm
KUBERNETES_PORT_443_TCP_PROTO=tcp
KUBERNETES_PORT_443_TCP_ADDR=10.96.0.1
KUBERNETES_SERVICE_HOST=10.96.0.1
KUBERNETES_PORT_443_TCP_PORT=443
KUBERNETES_SERVICE_PORT_HTTPS=443
KUBERNETES_PORT=tcp://10.96.0.1:443
KUBERNETES_PORT_443_TCP=tcp://10.96.0.1:443
KUBERNETES_SERVICE_PORT=443
NPM_CONFIG_LOGLEVEL=info
NODE_VERSION=6.3.1
HOME=/root
> kubectl exec -ti $PODNAME bash
kubectl exec [POD] [COMMAND] is DEPRECATED and will be removed in a future version. Use kubectl exec [POD] -- [COMMAND] instead.
root@kubernetes-bootcamp-57978f5f5d-z8vsm:/# exit
exit

4. Expose your app publicly

Step 1 Create a new service
> kubectl get pods
NAME                                   READY   STATUS    RESTARTS   AGE
kubernetes-bootcamp-57978f5f5d-z8vsm   1/1     Running   1          95m
❯ kubectl get services
NAME             TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)          AGE
kubernetes       ClusterIP   10.96.0.1       <none>        443/TCP          6d
> kubectl expose deployment/kubernetes-bootcamp --type="NodePort" --port 8080
service/kubernetes-bootcamp exposed
> kubectl get services
NAME                  TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)          AGE
kubernetes            ClusterIP   10.96.0.1       <none>        443/TCP          6d
kubernetes-bootcamp   NodePort    10.98.244.121   <none>        8080:31603/TCP   3m58s
> kubectl describe services/kubernetes-bootcamp
Name:                     kubernetes-bootcamp
Namespace:                default
Labels:                   app=kubernetes-bootcamp
Annotations:              <none>
Selector:                 app=kubernetes-bootcamp
Type:                     NodePort
IP Families:              <none>
IP:                       10.98.244.121
IPs:                      10.98.244.121
Port:                     <unset>  8080/TCP
TargetPort:               8080/TCP
NodePort:                 <unset>  31603/TCP
Endpoints:                172.17.0.5:8080
Session Affinity:         None
External Traffic Policy:  Cluster
Events:                   <none>
> $NODEPORT=kubectl get services/kubernetes-bootcamp -o go-template='{{(index .spec.ports 0).nodePort}}'
❯ $NODEPORT
31603
Step 2: Using labels
> kubectl describe deployment
Name:                   kubernetes-bootcamp
Namespace:              default
CreationTimestamp:      Thu, 31 Dec 2020 09:49:43 +0100
Labels:                 app=kubernetes-bootcamp
Annotations:            deployment.kubernetes.io/revision: 1
Selector:               app=kubernetes-bootcamp
Replicas:               1 desired | 1 updated | 1 total | 1 available | 0 unavailable
StrategyType:           RollingUpdate
MinReadySeconds:        0
RollingUpdateStrategy:  25% max unavailable, 25% max surge
Pod Template:
  Labels:  app=kubernetes-bootcamp
  Containers:
   kubernetes-bootcamp:
    Image:        gcr.io/google-samples/kubernetes-bootcamp:v1
    Port:         <none>
    Host Port:    <none>
    Environment:  <none>
    Mounts:       <none>
  Volumes:        <none>
Conditions:
  Type           Status  Reason
  ----           ------  ------
  Progressing    True    NewReplicaSetAvailable
  Available      True    MinimumReplicasAvailable
OldReplicaSets:  <none>
NewReplicaSet:   kubernetes-bootcamp-57978f5f5d (1/1 replicas created)
Events:          <none>
> kubectl get pods -l app=kubernetes-bootcamp
NAME                                   READY   STATUS    RESTARTS   AGE
kubernetes-bootcamp-57978f5f5d-z8vsm   1/1     Running   1          31h
> kubectl get services -l app=kubernetes-bootcamp
NAME                  TYPE       CLUSTER-IP      EXTERNAL-IP   PORT(S)          AGE
kubernetes-bootcamp   NodePort   10.98.244.121   <none>        8080:31603/TCP   30h
> $POD_NAME=kubectl get pods -o go-template --template '{{range .items}}{{.metadata.name}}{{end}}'
❯ $POD_NAME
kubernetes-bootcamp-57978f5f5d-z8vsm
> kubectl label pod $POD_NAME app=v1
> kubectl label pod $POD_NAME app=v1
error: 'app' already has a value (kubernetes-bootcamp), and --overwrite is false
❯ kubectl label pod $POD_NAME app=v1 --overwrite
pod/kubernetes-bootcamp-57978f5f5d-z8vsm labeled
> kubectl get pods -l app=v1
NAME                                   READY   STATUS    RESTARTS   AGE
kubernetes-bootcamp-57978f5f5d-z8vsm   1/1     Running   1          31h
Step 3: Deleting a service
> kubectl get services
NAME                  TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)          AGE
kubernetes            ClusterIP   10.96.0.1       <none>        443/TCP          7d6h
kubernetes-bootcamp   NodePort    10.98.244.121   <none>        8080:31603/TCP   30h
❯ kubectl delete service -l app=kubernetes-bootcamp
service "kubernetes-bootcamp" deleted

Not reachable from outside

> curl $(minikube ip):$NODE_PORT

Reachable from inside

> kubectl exec -ti $POD_NAME -- curl localhost:8080
Hello Kubernetes bootcamp! | Running on: kubernetes-bootcamp-57978f5f5d-z8vsm | v=1

5. Scale up your app

Step 1: Scaling a deployment

To list your deployments 

> kubectl get deployments
NAME                  READY   UP-TO-DATE   AVAILABLE   AGE
kubernetes-bootcamp   1/1     1            1           32h
> kubectl get rs
NAME                             DESIRED   CURRENT   READY   AGE
kubernetes-bootcamp-57978f5f5d   1         1         1       32h
> kubectl scale deployments/kubernetes-bootcamp --replicas=4
deployment.apps/kubernetes-bootcamp scaled
> kubectl get rs
NAME                             DESIRED   CURRENT   READY   AGE
kubernetes-bootcamp-57978f5f5d   4         4         4       32h
> kubectl get deployments
NAME                  READY   UP-TO-DATE   AVAILABLE   AGE
kubernetes-bootcamp   4/4     4            4           32h
> kubectl get pods -o wide
NAME                                   READY   STATUS    RESTARTS   AGE     IP           NODE       NOMINATED NODE   READINESS GATES
kubernetes-bootcamp-57978f5f5d-9fwnz   1/1     Running   0          28m     172.17.0.6   minikube   <none>           <none>
kubernetes-bootcamp-57978f5f5d-dgvm4   1/1     Running   0          6m33s   172.17.0.8   minikube   <none>           <none>
kubernetes-bootcamp-57978f5f5d-qh686   1/1     Running   0          6m33s   172.17.0.9   minikube   <none>           <none>
kubernetes-bootcamp-57978f5f5d-wx9zg   1/1     Running   0          6m33s   172.17.0.7   minikube   <none>           <none>
kubernetes-bootcamp-57978f5f5d-z8vsm   1/1     Running   1          32h     172.17.0.5   minikube   <none>           <none>
> kubectl describe deployments/kubernetes-bootcamp
Step 2: Load Balancing

Create service if desired

> kubectl expose deployment/kubernetes-bootcamp --type="NodePort" --port 8080
> $NODE_PORT=kubectl get services/kubernetes-bootcamp -o go-template='{{(index .spec.ports 0).nodePort}}'
❯ $NODE_PORT
31937
> $NODE_IP=minikube ip
Step 3: Scale Down
> kubectl get deployments
NAME                  READY   UP-TO-DATE   AVAILABLE   AGE
kubernetes-bootcamp   4/4     4            4           32h
❯ kubectl scale deployments/kubernetes-bootcamp --replicas=2
deployment.apps/kubernetes-bootcamp scaled
❯ kubectl get deployments
NAME                  READY   UP-TO-DATE   AVAILABLE   AGE
kubernetes-bootcamp   2/2     2            2           32h
>  kubectl get pods -o wide
NAME                                   READY   STATUS    RESTARTS   AGE   IP           NODE       NOMINATED NODE   READINESS GATES
kubernetes-bootcamp-57978f5f5d-9fwnz   1/1     Running   0          48m   172.17.0.6   minikube   <none>           <none>
kubernetes-bootcamp-57978f5f5d-wx9zg   1/1     Running   0          26m   172.17.0.7   minikube   <none>           <none>
kubernetes-bootcamp-57978f5f5d-z8vsm   1/1     Running   1          32h   172.17.0.5   minikube   <none>           <none>

6. Update your app