Migration of kubernetes master node from 1 server to another server

Following github issue mentioned in the comments and IP address changes in Kubernetes Master Node:

1. Verify your etcd data directory looking into etcd pod in kube-system namespace:

(default values using k8s v1.17.0 created with kubeadm),

    volumeMounts:
    - mountPath: /var/lib/etcd
      name: etcd-data

2. Preparation:

• copy /etc/kubernetes/pki from Master1 to the new Master2:

    #create backup directory in Master2,
    mkdir ~/backup

    #copy from Master1 all key,crt files into the Master2 
    sudo scp -r /etc/kubernetes/pki  [email protected]:~/backup

• On Master2 remove certs with keys that have the old IP address for apiserver and etcd cert:

    ./etcd/peer.crt
    ./apiserver.crt

    rm ~/backup/pki/{apiserver.*,etcd/peer.*}

• move pki directory to /etc/kubernetes

 cp -r ~/backup/pki  /etc/kubernetes/

3. On Master1 create etcd snapshot:

Verify your API version:

kubectl exec -it etcd-Master1 -n kube-system -- etcdctl  version

etcdctl version: 3.4.3
API version: 3.4

• using current etcd pod:

    kubectl exec -it etcd-master1 -n kube-system --  etcdctl --endpoints https://127.0.0.1:2379 --cacert=/etc/kubernetes/pki/etcd/ca.crt --cert=/etc/kubernetes/pki/etcd/server.crt --key /etc/kubernetes/pki/etcd/server.key snapshot save /var/lib/etcd/snapshot1.db

• using or using etcdctl binaries:

    ETCDCTL_API=3 etcdctl --endpoints https://127.0.0.1:2379 --cacert=/etc/kubernetes/pki/etcd/ca.crt --cert=/etc/kubernetes/pki/etcd/server.crt --key /etc/kubernetes/pki/etcd/server.key snapshot save /var/lib/etcd/snapshot1.db

4. Copy created snapshot from Master1 to Master2 backup directory:

scp ./snapshot1.db  [email protected]:~/backup

5. Prepare Kubeadm config in order to reflect Master1 configuration:

apiVersion: kubeadm.k8s.io/v1beta2
kind: InitConfiguration
localAPIEndpoint:
  advertiseAddress: x.x.x.x
  bindPort: 6443
nodeRegistration:
  name: master2
  taints: []     # Removing all taints from Master2 node.
---
apiServer:
  timeoutForControlPlane: 4m0s
apiVersion: kubeadm.k8s.io/v1beta2
certificatesDir: /etc/kubernetes/pki
clusterName: kubernetes
controllerManager: {}
dns:
  type: CoreDNS
etcd:
  local:
    dataDir: /var/lib/etcd
imageRepository: k8s.gcr.io
kind: ClusterConfiguration
kubernetesVersion: v1.17.0
networking:
  dnsDomain: cluster.local
  podSubnet: 10.0.0.0/16
  serviceSubnet: 10.96.0.0/12
scheduler: {}

6. Restore snapshot:

• using etcd:3.4.3-0 docker image:

    docker run --rm 
        -v $(pwd):/backup 
        -v /var/lib/etcd:/var/lib/etcd 
        --env ETCDCTL_API=3 
        k8s.gcr.io/etcd:3.4.3-0 
        /bin/sh -c "etcdctl snapshot restore './snapshot1.db' ; mv /default.etcd/member/ /var/lib/etcd/"

• or using etcdctl binaries:

    ETCDCTL_API=3 etcdctl --endpoints https://127.0.0.1:2379 snapshot restore  './snapshot1.db' ; mv ./default.etcd/member/ /var/lib/etcd/

7. Initialize Master2:

    sudo kubeadm init --ignore-preflight-errors=DirAvailable--var-lib-etcd --config kubeadm-config.yaml
    # kubeadm-config.yaml prepared in 5 step.

• notice:

[WARNING DirAvailable--var-lib-etcd]: /var/lib/etcd is not empty
[certs] Generating "apiserver" certificate and key
[certs] apiserver serving cert is signed for DNS names [master2 kubernetes kubernetes.default kubernetes.default.svc kubernetes.default.svc.cluster.local] and IPs [10.96.0.1 master2_IP]
[certs] Generating "etcd/server" certificate and key
[certs] etcd/server serving cert is signed for DNS names [master2 localhost] and IPs [master2_ip 127.0.0.1 ::1]
[certs] Generating "etcd/peer" certificate and key
[certs] etcd/peer serving cert is signed for DNS names [master2 localhost] and IPs [master2_ip 127.0.0.1 ::1]
.
.
.  
  Your Kubernetes control-plane has initialized successfully!
      mkdir -p $HOME/.kube
      sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
      sudo chown $(id -u):$(id -g) $HOME/.kube/config

• After k8s object verification (short example):

    kubectl get nodes
    kuebctl get pods - owide
    kuebctl get pods -n kube-system -o wide
    systemctl status kubelet 

• If all deployed k8s objects like pods,deployments etc, were moved into your new Master2 node:

    kubectl drain Master1
    kubectl delete node Master1

---

Note:

In addition please consider Creating Highly Available clusters in this setup you should have possibility to more than 1 master, in this configuration you can create/remove additional control plane nodes in more safely way.

• Docs
• Tutorial
• Documentation Operating etcd clusters for Kubernetes