このセクションでは、Kubernetes クラスタの初期化について紹介します。初期化することで、Master と Node サーバー間で Kubernetes クラスタを組むことができます。
ここでは、Kubernetes Master × 1台、Kubernetes Node × 2台のクラスター構成を前提にしています。
Master サーバーでの作業
hosts 設定ファイル（ /etc/hosts ）を編集し、Master と Node サーバー の名前解決ができるようにしておきます。
[root@kube-master ~]# vi /etc/hosts （下記 設定を追加） # kubernetes 192.168.25.100 kube-master 192.168.25.101 kube-work1 192.168.25.102 kube-work2
Master で Kubernetes のクラスタを構成するためのコマンドを実行します。 ここでは、クラスタ内ネットワーク（ Pod ネットワーク）用に Flannel を利用するために – – pod-network-cidr オプションで 10.224.0.0/16 を指定しています。 Flannel を使用する場合は、10.224.0.0/16 固定となります。
[root@kube-master ~]# kubeadm init --pod-network-cidr=10.244.0.0/16 [init] Using Kubernetes version: v1.13.1 [preflight] Running pre-flight checks [WARNING Firewalld]: firewalld is active, please ensure ports [6443 10250] are open or your cluster may not function correctly [WARNING SystemVerification]: this Docker version is not on the list of validated versions: 18.09.0. Latest validated version: 18.06 [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] Activating the kubelet service [certs] Using certificateDir folder "/etc/kubernetes/pki" [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/peer" certificate and key [certs] etcd/peer serving cert is signed for DNS names [kube-master localhost] and IPs [192.168.25.100 127.0.0.1 ::1] [certs] Generating "etcd/healthcheck-client" certificate and key [certs] Generating "etcd/server" certificate and key [certs] etcd/server serving cert is signed for DNS names [kube-master localhost] and IPs [192.168.25.100 127.0.0.1 ::1] [certs] Generating "apiserver-etcd-client" certificate and key [certs] Generating "ca" certificate and key [certs] Generating "apiserver" certificate and key [certs] apiserver serving cert is signed for DNS names [kube-master kubernetes kubernetes.default kubernetes.default.svc kubernetes.default.svc.cluster.local] and IPs [10.96.0.1 192.168.25.100] [certs] Generating "apiserver-kubelet-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" [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 19.001824 seconds [uploadconfig] storing the configuration used in ConfigMap "kubeadm-config" in the "kube-system" Namespace [kubelet] Creating a ConfigMap "kubelet-config-1.13" in namespace kube-system with the configuration for the kubelets in the cluster [patchnode] Uploading the CRI Socket information "/var/run/dockershim.sock" to the Node API object "kube-master" as an annotation [mark-control-plane] Marking the node kube-master as control-plane by adding the label "node-role.kubernetes.io/master=''" [mark-control-plane] Marking the node kube-master as control-plane by adding the taints [node-role.kubernetes.io/master:NoSchedule] [bootstrap-token] Using token: 6957gq.686kkrgapewsvu3s [bootstrap-token] Configuring bootstrap tokens, cluster-info ConfigMap, RBAC Roles [bootstraptoken] configured RBAC rules to allow Node Bootstrap tokens to post CSRs in order for nodes to get long term certificate credentials [bootstraptoken] configured RBAC rules to allow the csrapprover controller automatically approve CSRs from a Node Bootstrap Token [bootstraptoken] configured RBAC rules to allow certificate rotation for all node client certificates in the cluster [bootstraptoken] creating the "cluster-info" ConfigMap in the "kube-public" namespace [addons] Applied essential addon: CoreDNS [addons] Applied essential addon: kube-proxy Your Kubernetes master 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) $HOME/.kube/config You should now deploy a pod network to the cluster. Run "kubectl apply -f [podnetwork].yaml" with one of the options listed at: https://kubernetes.io/docs/concepts/cluster-administration/addons/ You can now join any number of machines by running the following on each node as root: kubeadm join 192.168.25.100:6443 --token 6957gq.686kkrgapewsvu3s --discovery-token-ca-cert-hash sha256:737497defe8e557b03da02e539bc991be3ab0ce7eb4f972a37388325a94d30b3 [root@kube-master ~]#
kubeadm init コマンド実行結果に記述される下記のコマンドは、Node を Kubernetes クラスタに参加させるために必要となるため、控えておきます。
kubeadm join 192.168.25.100:6443 --token w12ue5.ltptzgiwncp5lrev --discovery-token-ca-cert-hash sha256:13b544eb7776dca2c842a495ba84c1764c8cbfae5bf812f77124d843018d967b
rootユーザで kubectl を実行するために環境変数を指定します。
[root@kube-master ~]# export KUBECONFIG=/etc/kubernetes/admin.conf [root@kube-master ~]#
.bash_profileに環境変数を指定します。
[root@kube-master ~]# cat <<'EOF' > /root/.bash_profile
# .bash_profile
# Get the aliases and functions
if [ -f ~/.bashrc ]; then
. ~/.bashrc
fi
# User specific environment and startup programs
PATH=$PATH:$HOME/bin
export PATH
# add for kubernetes
export KUBECONFIG=/etc/kubernetes/admin.conf
EOF
[root@kube-master ~]#
Master サーバー 上でノードの状態を確認します。ここでは、Master サーバーであるkube-master ノードが確認できます。
[root@kube-master ~]# kubectl get nodes NAME STATUS ROLES AGE VERSION kube-master NotReady master 42s v1.13.1 [root@kube-master ~]#
Master サーバー上で全てネームスペースの Pod の状態を確認します。ここでは、3つの Pod が確認でき、coredns が Pending の状態になっています。
[root@kube-master ~]# kubectl get pods --all-namespaces NAMESPACE NAME READY STATUS RESTARTS AGE kube-system coredns-86c58d9df4-jrvm4 0/1 Pending 0 28s kube-system coredns-86c58d9df4-s9pkg 0/1 Pending 0 28s kube-system kube-proxy-bsw84 1/1 Running 0 27s [root@kube-master ~]#
Kubernetes クラスタで必要となる TCP 6443 通信をファイアウォールで許可します。
[root@kube-master ~]# firewall-cmd --add-port=6443/tcp --zone=public --permanent success [root@kube-master ~]#
ファイアウォールで TCP 6443 が許可された状態になっていることを確認します。
[root@kube-master ~]# firewall-cmd --list-port --zone=public --permanent 6443/tcp [root@kube-master ~]#
ファイアウォールをリロードし、設定を反映します。
[root@kube-master ~]# firewall-cmd --reload success [root@kube-master ~]#
Node サーバーでの作業
一つ目の Nodeサーバー（ kube-work1 ）で Master のクラスタに参加するようにします。
[root@kube-work1 ~]# kubeadm join 192.168.25.100:6443 --token 6957gq.686kkrgapewsvu3s --discovery-token-ca-cert-hash sha256:737497defe8e557b03da02e539bc991be3ab0ce7eb4f972a37388325a94d30b3 [preflight] Running pre-flight checks [WARNING SystemVerification]: this Docker version is not on the list of validated versions: 18.09.0. Latest validated version: 18.06 [discovery] Trying to connect to API Server "192.168.25.100:6443" [discovery] Created cluster-info discovery client, requesting info from "https://192.168.25.100:6443" [discovery] Requesting info from "https://192.168.25.100:6443" again to validate TLS against the pinned public key [discovery] Cluster info signature and contents are valid and TLS certificate validates against pinned roots, will use API Server "192.168.25.100:6443" [discovery] Successfully established connection with API Server "192.168.25.100:6443" [join] Reading configuration from the cluster... [join] FYI: You can look at this config file with 'kubectl -n kube-system get cm kubeadm-config -oyaml' [kubelet] Downloading configuration for the kubelet from the "kubelet-config-1.13" 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] Activating the kubelet service [tlsbootstrap] Waiting for the kubelet to perform the TLS Bootstrap... [patchnode] Uploading the CRI Socket information "/var/run/dockershim.sock" to the Node API object "kube-work1" as an annotation 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 master to see this node join the cluster. [root@kube-work1 ~]#
二つ目の Nodeサーバー（ kube-work2 ）でも Master のクラスタに参加するようにします。
[root@kube-work2 ~]# kubeadm join 192.168.25.100:6443 --token 6957gq.686kkrgapewsvu3s --discovery-token-ca-cert-hash sha256:737497defe8e557b03da02e539bc991be3ab0ce7eb4f972a37388325a94d30b3 [preflight] Running pre-flight checks [WARNING SystemVerification]: this Docker version is not on the list of validated versions: 18.09.0. Latest validated version: 18.06 [discovery] Trying to connect to API Server "192.168.25.100:6443" [discovery] Created cluster-info discovery client, requesting info from "https://192.168.25.100:6443" [discovery] Requesting info from "https://192.168.25.100:6443" again to validate TLS against the pinned public key [discovery] Cluster info signature and contents are valid and TLS certificate validates against pinned roots, will use API Server "192.168.25.100:6443" [discovery] Successfully established connection with API Server "192.168.25.100:6443" [join] Reading configuration from the cluster... [join] FYI: You can look at this config file with 'kubectl -n kube-system get cm kubeadm-config -oyaml' [kubelet] Downloading configuration for the kubelet from the "kubelet-config-1.13" 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] Activating the kubelet service [tlsbootstrap] Waiting for the kubelet to perform the TLS Bootstrap... [patchnode] Uploading the CRI Socket information "/var/run/dockershim.sock" to the Node API object "kube-work2" as an annotation 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 master to see this node join the cluster. [root@kube-work2 ~]#
Kubernetes クラスタの動作確認
Master サーバー 上でノードの状態を確認します。Master サーバーであるkube-master ノード と Node サーバーである kube-work1 と kube-work2 ノードが確認できます。 この時点では、各ノードの STATUS は NotReady のままになっています。
[root@kube-master ~]# kubectl get nodes NAME STATUS ROLES AGE VERSION kube-master NotReady master 8m2s v1.13.1 kube-work1 NotReady <none> 82s v1.13.1 kube-work2 NotReady <none> 87s v1.13.1 [root@kube-master ~]#
Master サーバー上で全てネームスペースの Pod の状態を確認します。ここでは、9つの Pod が確認でき、coredns が ContainerCreating の状態になっています。
[root@kube-master ~]# kubectl get pods --all-namespaces NAMESPACE NAME READY STATUS RESTARTS AGE kube-system coredns-86c58d9df4-fvsjf 0/1 ContainerCreating 0 7m23s kube-system coredns-86c58d9df4-nnbb5 0/1 ContainerCreating 0 12m kube-system etcd-kube-master 1/1 Running 0 11m kube-system kube-apiserver-kube-master 1/1 Running 0 11m kube-system kube-controller-manager-kube-master 1/1 Running 0 11m kube-system kube-proxy-jt4jq 1/1 Running 0 12m kube-system kube-proxy-tll9v 1/1 Running 0 6m2s kube-system kube-proxy-tzs4v 1/1 Running 0 6m7s kube-system kube-scheduler-kube-master 1/1 Running 0 11m [root@kube-master ~]#