[kubernetes] 쿠버네티스 클러스터 구성(CentOS 7)

쿠버네티스 클러스터 구성(CentOS 7)

시스템 구성

HOSTNAME	IP	ROLE	비고
k8s-master	192.168.0.101	control-plane node
k8s-node1	192.168.0.102	worker node
k8s-node2	192.168.0.103	worker node

쿠버네티스(kubeadm) 설치를 위한 사전 작업

• docker 설치 및 활성화

$ curl -s https://get.docker.com | sudo sh

$ systemctl enable --now docker

$ docker version
Client: Docker Engine - Community
 Version:           20.10.10
 API version:       1.41
 Go version:        go1.16.9
 Git commit:        b485636
 Built:             Mon Oct 25 07:44:50 2021
 OS/Arch:           linux/amd64
 Context:           default
 Experimental:      true

Server: Docker Engine - Community
 Engine:
  Version:          20.10.10
  API version:      1.41 (minimum version 1.12)
  Go version:       go1.16.9
  Git commit:       e2f740d
  Built:            Mon Oct 25 07:43:13 2021
  OS/Arch:          linux/amd64
  Experimental:     false
 containerd:
  Version:          1.4.11
  GitCommit:        5b46e404f6b9f661a205e28d59c982d3634148f8
 runc:
  Version:          1.0.2
  GitCommit:        v1.0.2-0-g52b36a2
 docker-init:
  Version:          0.19.0
  GitCommit:        de40ad0

• SELINEX 비활성화

$ setenforce 0

$ sed -i 's/^SELINUX=enforcing$/SELINUX=disabled/' /etc/selinux/config

• SWAP 비활성화

$ swapoff -a

$ sed -i '/ swap / s/^\(.*\)$/#\1/g' /etc/fstab

• 방화벽 끄기

$ systemctl disable firewalld

$ systemctl stop firewalld

• IPTABLES 설정
  - br_netfilter 모듈이 로드되었는지 확인
  - sysctl.conf에서 net.bridge.bridge-nf-call-iptables 값을 1로 설정

$ 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

호스트(/etc/hosts) 파일 편집

$ cat <<EOF >> /etc/hosts
192.168.0.101 k8s-master
192.168.0.102 k8s-node1
192.168.0.103 k8s-node2
EOF

kubeadm, kubelet, kubectl 설치

kubernetes.repo 등록

$ cat <<EOF | sudo tee /etc/yum.repos.d/kubernetes.repo
[kubernetes]
name=Kubernetes
baseurl=https://packages.cloud.google.com/yum/repos/kubernetes-el7-\$basearch
enabled=1
gpgcheck=1
repo_gpgcheck=1
gpgkey=https://packages.cloud.google.com/yum/doc/yum-key.gpg https://packages.cloud.google.com/yum/doc/rpm-package-key.gpg
exclude=kubelet kubeadm kubectl
EOF

kubeadm, kubelet, kubectl 패키지 설치

$ yum install -y kubelet kubeadm kubectl --disableexcludes=kubernetes

$ systemctl enable --now kubelet

kubeadm, kubelet, kubectl 패키지 버전 정보

$ kubeadm version -o short
v1.22.3

$ kubectl version --short
Client Version: v1.22.3
Server Version: v1.22.3

$ kubelet --version
Kubernetes v1.22.3

daemon.json 편집

$ cat <<EOF | sudo tee /etc/docker/daemon.json
{
  "exec-opts": ["native.cgroupdriver=systemd"],
  "log-driver": "json-file",
  "log-opts": {
    "max-size": "100m"
  },
  "storage-driver": "overlay2",
  "storage-opts": [
    "overlay2.override_kernel_check=true"
  ]
}
EOF

control-plane node(master node)

$ kubeadm init --apiserver-advertise-address {k8s-master IP} --pod-network-cidr=172.31.0.0/16

[init] Using Kubernetes version: v1.22.3
[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'
[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 [k8s-master kubernetes kubernetes.default kubernetes.default.svc kubernetes.default.svc.cluster.local] and IPs [10.96.0.1 192.168.0.101]
[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 [k8s-master localhost] and IPs [192.168.0.101 127.0.0.1 ::1]
[certs] Generating "etcd/peer" certificate and key
[certs] etcd/peer serving cert is signed for DNS names [k8s-master localhost] and IPs [192.168.0.101 127.0.0.1 ::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
[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
[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"
[control-plane] Creating static Pod manifest for "kube-scheduler"
[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
[apiclient] All control plane components are healthy after 12.505516 seconds
[upload-config] Storing the configuration used in ConfigMap "kubeadm-config" in the "kube-system" Namespace
[kubelet] Creating a ConfigMap "kubelet-config-1.22" 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 k8s-master as control-plane by adding the labels: [node-role.kubernetes.io/master(deprecated) node-role.kubernetes.io/control-plane node.kubernetes.io/exclude-from-external-load-balancers]
[mark-control-plane] Marking the node k8s-master as control-plane by adding the taints [node-role.kubernetes.io/master:NoSchedule]
[bootstrap-token] Using token: 7md2wt.1h1xfuzk3xgn0lft
[bootstrap-token] Configuring bootstrap tokens, cluster-info ConfigMap, RBAC Roles
[bootstrap-token] configured RBAC rules to allow Node Bootstrap tokens to get nodes
[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

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:

kubeadm join 192.168.0.101:6443 --token 7md2wt.1h1xfuzk3xgn0lft \
        --discovery-token-ca-cert-hash sha256:709dd217e4c3b6698017a255f64e56e1d0e41bdb4090e27cf23265e06e341a95

worker node(k8s-node1, k8s-node2)

kubeadm join 192.168.0.101:6443 --token 7md2wt.1h1xfuzk3xgn0lft \
 --discovery-token-ca-cert-hash sha256:709dd217e4c3b6698017a255f64e56e1d0e41bdb4090e27cf23265e06e341a95

[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-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.

노드가 클러스터에 참여하는지 확인합니다.

$ kubectl get nodes
NAME         STATUS     ROLES                  AGE     VERSION
k8s-master   NotReady   control-plane,master   13m     v1.22.3
k8s-node1    NotReady   <none>                 7m23s   v1.22.3
k8s-node2    NotReady   <none>                 39s     v1.22.3

시간이 많이 흘러서... Ready 상태로 되었습니다.

$ kubectl get nodes
NAME         STATUS   ROLES                  AGE   VERSION
k8s-master   Ready    control-plane,master   21m   v1.22.3
k8s-node1    Ready    <none>                 15m   v1.22.3
k8s-node2    Ready    <none>                 9m    v1.22.3

Weave CNI 플러그인 설치

$ kubectl apply -f "https://cloud.weave.works/k8s/net?k8s-version=$(kubectl version | base64 | tr -d '\n')"

serviceaccount/weave-net created
clusterrole.rbac.authorization.k8s.io/weave-net created
clusterrolebinding.rbac.authorization.k8s.io/weave-net created
role.rbac.authorization.k8s.io/weave-net created
rolebinding.rbac.authorization.k8s.io/weave-net created
daemonset.apps/weave-net created

$ kubectl get pods --all-namespaces
NAMESPACE     NAME                                 READY   STATUS    RESTARTS      AGE
kube-system   coredns-78fcd69978-cf2v8             1/1     Running   0             19m
kube-system   coredns-78fcd69978-ptq2m             1/1     Running   0             19m
kube-system   etcd-k8s-master                      1/1     Running   2             19m
kube-system   kube-apiserver-k8s-master            1/1     Running   2             19m
kube-system   kube-controller-manager-k8s-master   1/1     Running   2             19m
kube-system   kube-proxy-2vjpv                     1/1     Running   0             19m
kube-system   kube-proxy-6mck9                     1/1     Running   0             7m20s
kube-system   kube-proxy-v7sbs                     1/1     Running   0             14m
kube-system   kube-scheduler-k8s-master            1/1     Running   3             19m
kube-system   weave-net-4xcqz                      2/2     Running   1 (43s ago)   71s
kube-system   weave-net-m6lw4                      2/2     Running   1 (47s ago)   71s
kube-system   weave-net-w8lpl                      2/2     Running   1 (48s ago)   71s