[cka] Cluster Installation using Kubeadm

1. Install the kubeadm and kubelet packages on the controlplane and node01 nodes.
Use the exact version of 1.30.0-1.1 for both.

 

1-1. set net.bridge.bridge-nf-call-iptables to 1

cat <<EOF | sudo tee /etc/modules-load.d/k8s.conf
br_netfilter
EOF

cat <<EOF | sudo tee /etc/sysctl.d/k8s.conf
net.bridge.bridge-nf-call-ip6tables = 1
net.bridge.bridge-nf-call-iptables = 1
EOF

sudo sysctl --system

 

1-2. install container runtime.

해당 연구실실습에서는 설치되어 있다. (The container runtime has already been installed on both nodes, so you may skip this step.)

 

1-3. Install kubeadm, kubectl and kubelet on all nodes

sudo apt-get update

sudo apt-get install -y apt-transport-https ca-certificates curl

curl -fsSL https://pkgs.k8s.io/core:/stable:/v1.30/deb/Release.key | sudo gpg --dearmor -o /etc/apt/keyrings/kubernetes-apt-keyring.gpg

echo 'deb [signed-by=/etc/apt/keyrings/kubernetes-apt-keyring.gpg] https://pkgs.k8s.io/core:/stable:/v1.30/deb/ /' | sudo tee /etc/apt/sources.list.d/kubernetes.list

sudo apt-get update

# To see the new version labels
sudo apt-cache madison kubeadm

sudo apt-get install -y kubelet=1.30.0-1.1 kubeadm=1.30.0-1.1 kubectl=1.30.0-1.1

sudo apt-mark hold kubelet kubeadm kubectl

 

위과정을 controlplane 과 node01 에서 각각 진행시킨다.

 

2. What is the version of kubelet installed?

controlplane ~ ➜  kubelet --version
Kubernetes v1.30.0

 

3. How many nodes are part of kubernetes cluster currently? Are you able to run kubectl get nodes?

 

controlplane ~ ✖ k get nodes -A
E0825 08:08:03.743519   27576 memcache.go:265] couldn't get current server API group list: the server could not find the requested resource
E0825 08:08:03.744542   27576 memcache.go:265] couldn't get current server API group list: the server could not find the requested resource
E0825 08:08:03.745555   27576 memcache.go:265] couldn't get current server API group list: the server could not find the requested resource
E0825 08:08:03.746575   27576 memcache.go:265] couldn't get current server API group list: the server could not find the requested resource
E0825 08:08:03.747556   27576 memcache.go:265] couldn't get current server API group list: the server could not find the requested resource
Error from server (NotFound): the server could not find the requested resource

 

answer : 0

 

4. Lets now bootstrap a kubernetes cluster using kubeadm. The latest version of Kubernetes will be installed.

 

5.

Initialize Control Plane Node (Master Node). 

Use the following options: 

 

1) apiserver-advertise-address - Use the IP address allocated to eth0 on the controlplane node

2) apiserver-cert-extra-sans - Set it to controlplane

3) pod-network-cidr - Set to 10.244.0.0/16

 

Once done, set up the default kubeconfig file and wait for node to be part of the cluster.

 

IP_ADDR=$(ip addr show eth0 | grep -oP '(?<=inet\s)\d+(\.\d+){3}')
kubeadm init --apiserver-cert-extra-sans=controlplane --apiserver-advertise-address $IP_ADDR --pod-network-cidr=10.244.0.0/16



설치 완료후

mkdir -p $HOME/.kube

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

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

 

 

6. Generate a kubeadm join token Or copy the one that was generated by kubeadm init command

 

7. Join node01 to the cluster using the join token

 

controlplane ~ ➜  kubeadm token create --print-join-command
kubeadm join 192.11.220.3:6443 --token wj1nt9.ozyj03w85ietw4rf --discovery-token-ca-cert-hash sha256:cb2dfc43275590a8a2149fa0b81f1eb9f1f1644f2399e4d350c3941059144b52 

controlplane ~ ➜  ssh node01^C

controlplane ~ ✖ ssh node01
Last login: Sun Aug 25 08:16:27 2024 from 192.11.220.4

node01 ~ ➜  kubeadm join 192.11.220.3:6443 --token wj1nt9.ozyj03w85ietw4rf --discovery-token-ca-cert-hash sha256:cb2dfc43275590a8a2149fa0b81f1eb9f1f1644f2399e4d350c3941059144b52
[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 -o yaml'
[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-check] Waiting for a healthy kubelet. This can take up to 4m0s
[kubelet-check] The kubelet is healthy after 1.001643599s
[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.

 

8. To install a network plugin, we will go with Flannel as the default choice. 

For inter-host communication, we will utilize the eth0 interface. 

Please ensure that the Flannel manifest includes the appropriate options for this configuration. 

Refer to the official documentation for the procedure.

 

 

8-1. Flannel yaml 설치파일 다운로드

# Download the original YAML file and save it as kube-flannel.yml
curl -LO https://raw.githubusercontent.com/flannel-io/flannel/v0.20.2/Documentation/kube-flannel.yml

 

8-2. 다운로드된 파일에서 해당 파일 추가. (네트워크 인터페이스 eht0 설정내용)

vi kube-flannel.yaml

## in kube-flannel.yaml

...
  args:
  - --ip-masq
  - --kube-subnet-mgr
  - --iface=eth0 # 항목추가
...

controlplane ~ ➜  k apply -f kube-flannel.yml 
namespace/kube-flannel 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 created

 

8-3. 설치확인.

# 설치전
controlplane ~ ➜  k get nodes
NAME           STATUS     ROLES           AGE    VERSION
controlplane   NotReady   control-plane   104s   v1.30.0
node01         NotReady   <none>          17s    v1.30.0



# 설치후
controlplane ~ ➜  k get nodes
NAME           STATUS   ROLES           AGE     VERSION
controlplane   Ready    control-plane   5m9s    v1.30.0
node01         Ready    <none>          3m42s   v1.30.0