kubectl cheat sheet

https://kubernetes.io/docs/setup/production-environment/tools/kubeadm/create-cluster-kubeadm/ https://kubecloud.io/setting-up-a-kubernetes-1-11-raspberry-pi-cluster-using-kubeadm-952bbda329c8

Initialise a Kubernetes control-plane node. CIDR required by flannel networking later.

[email protected]:/# kubeadm init --pod-network-cidr=10.244.0.0/16
W0311 12:36:59.643230    8155 validation.go:28] Cannot validate kube-proxy config - no validator is available
W0311 12:36:59.643396    8155 validation.go:28] Cannot validate kubelet config - no validator is available
[init] Using Kubernetes version: v1.17.3
[preflight] Running pre-flight checks
[preflight] Pulling images required for setting up a Kubernetes cluster
[preflight] This might take a minute or two, depending on the speed of your internet connection
[preflight] You can also perform this action in beforehand using 'kubeadm config images pull'
[kubelet-start] Writing kubelet environment file with flags to file "/var/lib/kubelet/kubeadm-flags.env"
[kubelet-start] Writing kubelet configuration to file "/var/lib/kubelet/config.yaml"
[kubelet-start] Starting the kubelet
[certs] Using certificateDir folder "/etc/kubernetes/pki"
[certs] Generating "ca" certificate and key
[certs] Generating "apiserver" certificate and key
[certs] apiserver serving cert is signed for DNS names [nano1.home.lan kubernetes kubernetes.default kubernetes.default.svc kubernetes.default.svc.cluster.local] and IPs [10.96.0.1 192.168.2.21]
[certs] Generating "apiserver-kubelet-client" certificate and key
[certs] Generating "front-proxy-ca" certificate and key
[certs] Generating "front-proxy-client" certificate and key
[certs] Generating "etcd/ca" certificate and key
[certs] Generating "etcd/server" certificate and key
[certs] etcd/server serving cert is signed for DNS names [nano1.home.lan localhost] and IPs [192.168.2.21 127.0.0.1 ::1]
[certs] Generating "etcd/peer" certificate and key
[certs] etcd/peer serving cert is signed for DNS names [nano1.home.lan localhost] and IPs [192.168.2.21 127.0.0.1 ::1]
[certs] Generating "etcd/healthcheck-client" certificate and key
[certs] Generating "apiserver-etcd-client" certificate and key
[certs] Generating "sa" key and public key
[kubeconfig] Using kubeconfig folder "/etc/kubernetes"
[kubeconfig] Writing "admin.conf" kubeconfig file
[kubeconfig] Writing "kubelet.conf" kubeconfig file
[kubeconfig] Writing "controller-manager.conf" kubeconfig file
[kubeconfig] Writing "scheduler.conf" kubeconfig file
[control-plane] Using manifest folder "/etc/kubernetes/manifests"
[control-plane] Creating static Pod manifest for "kube-apiserver"
[control-plane] Creating static Pod manifest for "kube-controller-manager"
W0311 12:39:37.242102    8155 manifests.go:214] the default kube-apiserver authorization-mode is "Node,RBAC"; using "Node,RBAC"
[control-plane] Creating static Pod manifest for "kube-scheduler"
W0311 12:39:37.247664    8155 manifests.go:214] the default kube-apiserver authorization-mode is "Node,RBAC"; using "Node,RBAC"
[etcd] Creating static Pod manifest for local etcd in "/etc/kubernetes/manifests"
[wait-control-plane] Waiting for the kubelet to boot up the control plane as static Pods from directory "/etc/kubernetes/manifests". This can take up to 4m0s
[kubelet-check] Initial timeout of 40s passed.
[apiclient] All control plane components are healthy after 64.509661 seconds
[upload-config] Storing the configuration used in ConfigMap "kubeadm-config" in the "kube-system" Namespace
[kubelet] Creating a ConfigMap "kubelet-config-1.17" in namespace kube-system with the configuration for the kubelets in the cluster
[upload-certs] Skipping phase. Please see --upload-certs
[mark-control-plane] Marking the node nano1.home.lan as control-plane by adding the label "node-role.kubernetes.io/master=''"
[mark-control-plane] Marking the node nano1.home.lan as control-plane by adding the taints [node-role.kubernetes.io/master:NoSchedule]
[bootstrap-token] Using token: 7r9n64.3c3x2j73e0axqgxk
[bootstrap-token] Configuring bootstrap tokens, cluster-info ConfigMap, RBAC Roles
[bootstrap-token] configured RBAC rules to allow Node Bootstrap tokens to post CSRs in order for nodes to get long term certificate credentials
[bootstrap-token] configured RBAC rules to allow the csrapprover controller automatically approve CSRs from a Node Bootstrap Token
[bootstrap-token] configured RBAC rules to allow certificate rotation for all node client certificates in the cluster
[bootstrap-token] Creating the "cluster-info" ConfigMap in the "kube-public" namespace
[kubelet-finalize] Updating "/etc/kubernetes/kubelet.conf" to point to a rotatable kubelet client certificate and key
[addons] Applied essential addon: CoreDNS
[addons] Applied essential addon: kube-proxy

Your Kubernetes control-plane has initialized successfully!

To start using your cluster, you need to run the following as a regular user:

  mkdir -p $HOME/.kube
  sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
  sudo chown $(id -u):$(id -g) $HOME/.kube/config

You should now deploy a pod network to the cluster.
Run "kubectl apply -f [podnetwork].yaml" with one of the options listed at:
  https://kubernetes.io/docs/concepts/cluster-administration/addons/

Then you can join any number of worker nodes by running the following on each as root:

kubeadm join 192.168.2.21:6443 --token 7r9n64.3c3x2j73e0axqgxk \
    --discovery-token-ca-cert-hash sha256:5d4fb62d6372b4bc2cfc044943d79ef8b8aa7ac342570d20c6dc48e1dbb44c67 

troubleshoot

kubectl describe po coredns-6955765f44-847hz -n kube-system

Setup environment

mkdir -p $HOME/.kube
sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
sudo chown $(id -u):$(id -g) $HOME/.kube/config

Check control-plane status

[email protected]:~# kubectl get pods --all-namespaces
NAMESPACE     NAME                                  READY   STATUS    RESTARTS   AGE
kube-system   coredns-6955765f44-ln6b2              1/1     Running   0          8m39s
kube-system   coredns-6955765f44-ml8bc              1/1     Running   0          8m39s
kube-system   etcd-nanopifire3                      1/1     Running   0          8m39s
kube-system   kube-apiserver-nanopifire3            1/1     Running   0          8m39s
kube-system   kube-controller-manager-nanopifire3   1/1     Running   2          8m39s
kube-system   kube-proxy-sfp8f                      1/1     Running   0          8m39s
kube-system   kube-scheduler-nanopifire3            1/1     Running   2          8m39s

Flannel network - Flannel is a very simple overlay network that satisfies Kubernetes requirements.

https://github.com/coreos/flannel/blob/master/Documentation/troubleshooting.md

when intialising the CIDR was defined.

–pod-network-cidr=10.244.0.0/16

review config

kubectl -n kube-system get cm kubeadm-config -oyaml

launch flannel

kubectl apply -f https://raw.githubusercontent.com/coreos/flannel/master/Documentation/kube-flannel.yml

[email protected]:~# kubectl apply -f https://raw.githubusercontent.com/coreos/flannel/master/Documentation/kube-flannel.yml
podsecuritypolicy.policy/psp.flannel.unprivileged created
clusterrole.rbac.authorization.k8s.io/flannel created
clusterrolebinding.rbac.authorization.k8s.io/flannel created
serviceaccount/flannel created
configmap/kube-flannel-cfg created
daemonset.apps/kube-flannel-ds-amd64 created
daemonset.apps/kube-flannel-ds-arm64 created
daemonset.apps/kube-flannel-ds-arm created
daemonset.apps/kube-flannel-ds-ppc64le created

show pods

kubectl get pods –all-namespaces

[email protected]:~# kubectl get pods --all-namespaces
NAMESPACE     NAME                                  READY   STATUS    RESTARTS   AGE
kube-system   coredns-6955765f44-ln6b2              1/1     Running   0          11m
kube-system   coredns-6955765f44-ml8bc              1/1     Running   0          11m
kube-system   etcd-nanopifire3                      1/1     Running   0          11m
kube-system   kube-apiserver-nanopifire3            1/1     Running   0          11m
kube-system   kube-controller-manager-nanopifire3   1/1     Running   2          11m
kube-system   kube-flannel-ds-arm64-8dn2k           1/1     Running   0          3m17s
kube-system   kube-proxy-sfp8f                      1/1     Running   0          11m
kube-system   kube-scheduler-nanopifire3            1/1     Running   2          11m

troubleshoot

kubectl logs –namespace kube-system kube-flannel-ds-arm64-vhmvb -c kube-flannel

example config

/etc/cni/net.d/10-flannel.conflist

{
  "name": "cbr0",
  "plugins": [
    {
      "type": "flannel",
      "delegate": {
        "hairpinMode": true,
        "isDefaultGateway": true
      }
    },
    {
      "type": "portmap",
      "capabilities": {
        "portMappings": true
      }
    }
  ],
  "cniVersion": "0.2.0"
}

add nodes

[email protected]:~# kubeadm join 192.168.2.21:6443 --token 7r9n64.3c3x2j73e0axqgxk \
>     --discovery-token-ca-cert-hash sha256:5d4fb62d6372b4bc2cfc044943d79ef8b8aa7ac342570d20c6dc48e1dbb44c67 
W0311 12:52:53.410629   14815 join.go:346] [preflight] WARNING: JoinControlPane.controlPlane settings will be ignored when control-plane flag is not set.
[preflight] Running pre-flight checks
[preflight] Reading configuration from the cluster...
[preflight] FYI: You can look at this config file with 'kubectl -n kube-system get cm kubeadm-config -oyaml'
[kubelet-start] Downloading configuration for the kubelet from the "kubelet-config-1.17" ConfigMap in the kube-system namespace
[kubelet-start] Writing kubelet configuration to file "/var/lib/kubelet/config.yaml"
[kubelet-start] Writing kubelet environment file with flags to file "/var/lib/kubelet/kubeadm-flags.env"
[kubelet-start] Starting the kubelet
[kubelet-start] Waiting for the kubelet to perform the TLS Bootstrap...

This node has joined the cluster:
* Certificate signing request was sent to apiserver and a response was received.
* The Kubelet was informed of the new secure connection details.

Run 'kubectl get nodes' on the control-plane to see this node join the cluster.
[email protected]:~# kubeadm join 192.168.2.21:6443 --token 7r9n64.3c3x2j73e0axqgxk \
>     --discovery-token-ca-cert-hash sha256:5d4fb62d6372b4bc2cfc044943d79ef8b8aa7ac342570d20c6dc48e1dbb44c67 
W0311 12:52:54.731761   14780 join.go:346] [preflight] WARNING: JoinControlPane.controlPlane settings will be ignored when control-plane flag is not set.
[preflight] Running pre-flight checks
[preflight] Reading configuration from the cluster...
[preflight] FYI: You can look at this config file with 'kubectl -n kube-system get cm kubeadm-config -oyaml'
[kubelet-start] Downloading configuration for the kubelet from the "kubelet-config-1.17" ConfigMap in the kube-system namespace
[kubelet-start] Writing kubelet configuration to file "/var/lib/kubelet/config.yaml"
[kubelet-start] Writing kubelet environment file with flags to file "/var/lib/kubelet/kubeadm-flags.env"
[kubelet-start] Starting the kubelet
[kubelet-start] Waiting for the kubelet to perform the TLS Bootstrap...

This node has joined the cluster:
* Certificate signing request was sent to apiserver and a response was received.
* The Kubelet was informed of the new secure connection details.

Run 'kubectl get nodes' on the control-plane to see this node join the cluster.

From the control-plane node (nano1.home.lan)

[email protected]:/etc# kubectl get nodes
NAME             STATUS   ROLES    AGE    VERSION
nano1.home.lan   Ready    master   14m    v1.17.3
nano2.home.lan   Ready    <none>   118s   v1.17.3
nano3.home.lan   Ready    <none>   116s   v1.17.3

nginx-ingress

https://kubernetes.github.io/ingress-nginx/deploy/

curl -O https://raw.githubusercontent.com/kubernetes/ingress-nginx/master/deploy/static/mandatory.yaml
kubectl apply -f mandatory.yaml

Update image too arm64

image: quay.io/kubernetes-ingress-controller/nginx-ingress-controller-arm64:0.30.0

[email protected]:~# kubectl apply -f mandatory.yaml
namespace/ingress-nginx created
configmap/nginx-configuration created
configmap/tcp-services created
configmap/udp-services created
serviceaccount/nginx-ingress-serviceaccount created
clusterrole.rbac.authorization.k8s.io/nginx-ingress-clusterrole created
role.rbac.authorization.k8s.io/nginx-ingress-role created
rolebinding.rbac.authorization.k8s.io/nginx-ingress-role-nisa-binding created
clusterrolebinding.rbac.authorization.k8s.io/nginx-ingress-clusterrole-nisa-binding created
deployment.apps/nginx-ingress-controller created
limitrange/ingress-nginx created

get status

[email protected]:~# kubectl get pods -n ingress-nginx
NAME                                        READY   STATUS    RESTARTS   AGE
nginx-ingress-controller-5c486bc575-hmkh5   1/1     Running   0          2m52s
[email protected]:~# kubectl apply -f https://raw.githubusercontent.com/kubernetes/ingress-nginx/nginx-0.30.0/deploy/static/provider/baremetal/service-nodeport.yaml
service/ingress-nginx created

[email protected]:~# kubectl get pods --all-namespaces -l app.kubernetes.io/name=ingress-nginx --watch
NAMESPACE       NAME                                        READY   STATUS    RESTARTS   AGE
ingress-nginx   nginx-ingress-controller-5c486bc575-hmkh5   1/1     Running   0          5m31s
[email protected]:~# POD_NAMESPACE=ingress-nginx
[email protected]:~# POD_NAME=$(kubectl get pods -n $POD_NAMESPACE -l app.kubernetes.io/name=ingress-nginx -o jsonpath='{.items[0].metadata.name}')
[email protected]:~# 
[email protected]:~# kubectl exec -it $POD_NAME -n $POD_NAMESPACE -- /nginx-ingress-controller --version
-------------------------------------------------------------------------------
NGINX Ingress controller
  Release:       0.30.0
  Build:         git-7e65b90c4
  Repository:    https://github.com/kubernetes/ingress-nginx
  nginx version: nginx/1.17.8

-------------------------------------------------------------------------------
apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  name: nano-ingress
  annotations:
    nginx.ingress.kubernetes.io/rewrite-target: /
spec:
  rules:
  - http:
      paths:
      - path: /nginx-deployment
        backend:
          serviceName: nginx-deployment
          servicePort: 8080
      - path: /hello-world-go
        backend:
          serviceName: helloworld-v1 
          servicePort: 8080
apiVersion: v1
kind: Service
metadata:
  name: ingress-nginx
  namespace: ingress-nginx
  labels:
    app.kubernetes.io/name: ingress-nginx
    app.kubernetes.io/part-of: ingress-nginx
spec:
  type: NodePort
  ports:
    - name: http
      port: 80
      targetPort: 80
      protocol: TCP
    - name: https
      port: 443
      targetPort: 443
      protocol: TCP
  externalIPs:
    - 192.168.0.71
    - 192.168.0.72
    - 192.168.0.73
  selector:
    app.kubernetes.io/name: ingress-nginx
    app.kubernetes.io/part-of: ingress-nginx

4) prometheus monitoring

docker clean ups

docker rm -f $(docker ps -qa) docker rmi -f $(docker images -q) docker volume rm $(docker volume ls -q)

if reset and get cert errors

[email protected]:~# kubectl apply -f https://raw.githubusercontent.com/coreos/flannel/master/Documentation/kube-flannel.yml Unable to connect to the server: x509: certificate signed by unknown authority (possibly because of “crypto/rsa: verification error” while trying to verify candidate authority certificate “kubernetes”)

unset KUBECONFIG

export KUBECONFIG=/etc/kubernetes/admin.conf

mv $HOME/.kube $HOME/.kube.bak

mkdir $HOME/.kube

sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config

sudo chown $(id -u):$(id -g) $HOME/.kube/config