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Kubernetes : Configure Master Node
2021/05/11
 
Install Kubeadm to Configure Multi Nodes Kubernetes Cluster.
This example is based on the environment like follows.
-----------+---------------------------+--------------------------+------------
           |                           |                          |
       eth0|10.0.0.30              eth0|10.0.0.51             eth0|10.0.0.52
+----------+-----------+   +-----------+----------+   +-----------+----------+
|   [ dlp.srv.world ]  |   | [ node01.srv.world ] |   | [ node02.srv.world ] |
|      Master Node     |   |      Worker Node     |   |      Worker Node     |
+----------------------+   +----------------------+   +----------------------+

[1]
[2]
Configure initial setup on Master Node.
For [--apiserver-advertise-address] option, specify the IP address Kubernetes API server listens.
For [--pod-network-cidr] option, specify network which Pod Network uses.
There are some plugins for Pod Network. (refer to details below)
  ⇒ https://kubernetes.io/docs/concepts/cluster-administration/networking/
On this example, it selects Calico.
# need the same version on Kubernetes and CRI-O

[root@dlp ~]#
kubeadm init --apiserver-advertise-address=10.0.0.30 --pod-network-cidr=192.168.0.0/16 --cri-socket=unix:///var/run/crio/crio.sock --kubernetes-version=1.20.0

[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'
[certs] Using certificateDir folder "/etc/kubernetes/pki"
[certs] Generating "ca" certificate and key
[certs] Generating "apiserver" certificate and key

.....
.....

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

Alternatively, if you are the root user, you can run:

  export KUBECONFIG=/etc/kubernetes/admin.conf

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:

# the command below is necessary to run on Worker Node when he joins to the cluster, so remember it
kubeadm join 10.0.0.30:6443 --token xme2jq.gb2sgglicnpqqshv \
    --discovery-token-ca-cert-hash sha256:2f597590adfff75d6c1394cef5b5209b2e58f52c8c54b8a3630367ac3991fb59

# set cluster admin user

# if you set common user as cluster admin, login with it and run [sudo cp/chown ***]

root@dlp:~#
mkdir -p $HOME/.kube

root@dlp:~#
cp -i /etc/kubernetes/admin.conf $HOME/.kube/config

root@dlp:~#
chown $(id -u):$(id -g) $HOME/.kube/config
[3] Configure Pod Network with Calico.
[root@dlp ~]#
wget https://docs.projectcalico.org/manifests/calico.yaml

[root@dlp ~]#
kubectl apply -f calico.yaml

configmap/calico-config created
customresourcedefinition.apiextensions.k8s.io/bgpconfigurations.crd.projectcalico.org created
customresourcedefinition.apiextensions.k8s.io/bgppeers.crd.projectcalico.org created
customresourcedefinition.apiextensions.k8s.io/blockaffinities.crd.projectcalico.org created
customresourcedefinition.apiextensions.k8s.io/clusterinformations.crd.projectcalico.org created
customresourcedefinition.apiextensions.k8s.io/felixconfigurations.crd.projectcalico.org created
customresourcedefinition.apiextensions.k8s.io/globalnetworkpolicies.crd.projectcalico.org created
customresourcedefinition.apiextensions.k8s.io/globalnetworksets.crd.projectcalico.org created
customresourcedefinition.apiextensions.k8s.io/hostendpoints.crd.projectcalico.org created
customresourcedefinition.apiextensions.k8s.io/ipamblocks.crd.projectcalico.org created
customresourcedefinition.apiextensions.k8s.io/ipamconfigs.crd.projectcalico.org created
customresourcedefinition.apiextensions.k8s.io/ipamhandles.crd.projectcalico.org created
customresourcedefinition.apiextensions.k8s.io/ippools.crd.projectcalico.org created
customresourcedefinition.apiextensions.k8s.io/kubecontrollersconfigurations.crd.projectcalico.org created
customresourcedefinition.apiextensions.k8s.io/networkpolicies.crd.projectcalico.org created
customresourcedefinition.apiextensions.k8s.io/networksets.crd.projectcalico.org created
clusterrole.rbac.authorization.k8s.io/calico-kube-controllers created
clusterrolebinding.rbac.authorization.k8s.io/calico-kube-controllers created
clusterrole.rbac.authorization.k8s.io/calico-node created
clusterrolebinding.rbac.authorization.k8s.io/calico-node created
daemonset.apps/calico-node created
serviceaccount/calico-node created
deployment.apps/calico-kube-controllers created
serviceaccount/calico-kube-controllers created
poddisruptionbudget.policy/calico-kube-controllers created

# show state : OK if STATUS = Ready

[root@dlp ~]#
kubectl get nodes

NAME            STATUS   ROLES                  AGE     VERSION
dlp.srv.world   Ready    control-plane,master   3m27s   v1.20.5

# show state : OK if all are Running

[root@dlp ~]#
kubectl get pods -A

NAMESPACE     NAME                                       READY   STATUS    RESTARTS   AGE
kube-system   calico-kube-controllers-6d7b4db76c-6rp8z   1/1     Running   0          108s
kube-system   calico-node-494s2                          1/1     Running   0          108s
kube-system   coredns-74ff55c5b-2kdm9                    1/1     Running   0          3m19s
kube-system   coredns-74ff55c5b-dftgb                    1/1     Running   0          3m19s
kube-system   etcd-dlp.srv.world                         1/1     Running   0          3m31s
kube-system   kube-apiserver-dlp.srv.world               1/1     Running   0          3m31s
kube-system   kube-controller-manager-dlp.srv.world      1/1     Running   0          3m31s
kube-system   kube-proxy-pxwmg                           1/1     Running   0          3m19s
kube-system   kube-scheduler-dlp.srv.world               1/1     Running   0          3m31s
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