Install Kubeadm to Configure Multi Nodes Kubernetes Cluster.
This example is based on the environment like follows.
For System requirements, each Node has unique Hostname, MAC address, Product_uuid.
MAC address and Product_uuid are generally already unique one if you installed OS on physical machine or virtual machine with common procedure.
You can see Product_uuid with the command [dmidecode -s system-uuid].
-----------+---------------------------+--------------------------+------------
| | |
eth0|10.0.0.25 eth0|10.0.0.71 eth0|10.0.0.72
+----------+-----------+ +-----------+-----------+ +-----------+-----------+
| [ ctrl.srv.world ] | | [snode01.srv.world] | | [snode02.srv.world] |
| Control Plane | | Worker Node | | Worker Node |
+----------------------+ +-----------------------+ +-----------------------+[1]Install Containerd and apply some requirements on all Nodes.
root@ctrl:~# apt -y install containerd iptables apt-transport-https gnupg2 curl sudo
root@ctrl:~# cat > /etc/sysctl.d/99-k8s-cri.conf <<EOF
net.bridge.bridge-nf-call-iptables=1
net.bridge.bridge-nf-call-ip6tables=1
net.ipv4.ip_forward=1
EOF
root@ctrl:~# sysctl --system
root@ctrl:~# modprobe overlay; modprobe br_netfilter
root@ctrl:~# echo -e overlay\\nbr_netfilter > /etc/modules-load.d/k8s.conf
# needs [iptables-legacy] for iptables backend
# if nftables is enabled, change to [iptables-legacy]
root@ctrl:~# update-alternatives --config iptables
There are 2 choices for the alternative iptables (providing /usr/sbin/iptables).
Selection Path Priority Status
------------------------------------------------------------
* 0 /usr/sbin/iptables-nft 20 auto mode
1 /usr/sbin/iptables-legacy 10 manual mode
2 /usr/sbin/iptables-nft 20 manual mode
Press <enter> to keep the current choice[*], or type selection number: 1
update-alternatives: using /usr/sbin/iptables-legacy to provide /usr/sbin/iptables (iptables) in manual mode
# disable swap
root@ctrl:~# swapoff -a
root@ctrl:~# vi /etc/fstab
# comment out
#/dev/mapper/debian--vg-swap_1 none swap sw 0 0
# switch to Cgroup v1 (v2 is the default)
root@ctrl:~# vi /etc/default/grub
# line 10 : add
GRUB_CMDLINE_LINUX="systemd.unified_cgroup_hierarchy=0"
root@ctrl:~# update-grub
root@ctrl:~# reboot[2] Install Kubeadm, Kubelet, Kubectl on all Nodes.
root@ctrl:~# curl -fsSL https://packages.cloud.google.com/apt/doc/apt-key.gpg -o /etc/apt/keyrings/kubernetes-keyring.key
root@ctrl:~# echo "deb [signed-by=/etc/apt/keyrings/kubernetes-keyring.key] https://apt.kubernetes.io/ kubernetes-xenial main" | tee /etc/apt/sources.list.d/kubernetes.list
root@ctrl:~# apt update
root@ctrl:~# apt -y install kubelet=1.26.6-00 kubeadm=1.26.6-00 kubectl=1.26.6-00
root@ctrl:~# ln -s /opt/cni/bin /usr/lib/cni[3] Configure initial setup on Control Plane Node.
For [control-plane-endpoint], specify the Hostname or IP address that Etcd and Kubernetes API server are run.
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 uses Calico.
root@ctrl:~# kubeadm init --control-plane-endpoint=10.0.0.25 --pod-network-cidr=192.168.0.0/16 --cri-socket=unix:///run/containerd/containerd.sock
I0727 19:05:02.936396 1489 version.go:256] remote version is much newer: v1.27.4; falling back to: stable-1.26
[init] Using Kubernetes version: v1.26.7
[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 [ctrl.srv.world kubernetes kubernetes.default kubernetes.default.svc kubernetes.default.svc.cluster.local] and IPs [10.96.0.1 10.0.0.25]
[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 [ctrl.srv.world localhost] and IPs [10.0.0.25 127.0.0.1 ::1]
[certs] Generating "etcd/peer" certificate and key
[certs] etcd/peer serving cert is signed for DNS names [ctrl.srv.world localhost] and IPs [10.0.0.25 127.0.0.1 ::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 6.501887 seconds
[upload-config] Storing the configuration used in ConfigMap "kubeadm-config" in the "kube-system" Namespace
[kubelet] Creating a ConfigMap "kubelet-config" 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 ctrl.srv.world as control-plane by adding the labels: [node-role.kubernetes.io/control-plane node.kubernetes.io/exclude-from-external-load-balancers]
[mark-control-plane] Marking the node ctrl.srv.world as control-plane by adding the taints [node-role.kubernetes.io/control-plane:NoSchedule]
[bootstrap-token] Using token: q1xuoi.v6meo9irmuv9g0y1
[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/
You can now join any number of control-plane nodes by copying certificate authorities
and service account keys on each node and then running the following as root:
kubeadm join 10.0.0.25:6443 --token q1xuoi.v6meo9irmuv9g0y1 \
--discovery-token-ca-cert-hash sha256:1b96782423120e014e212197d34c56b029af1a8db85bf40a6602e19881bc7db1 \
--control-plane
Then you can join any number of worker nodes by running the following on each as root:
kubeadm join 10.0.0.25:6443 --token q1xuoi.v6meo9irmuv9g0y1 \
--discovery-token-ca-cert-hash sha256:1b96782423120e014e212197d34c56b029af1a8db85bf40a6602e19881bc7db1
# set cluster admin user
# if you set common user as cluster admin, login with it and run [sudo cp/chown ***]
root@ctrl:~# mkdir -p $HOME/.kube
root@ctrl:~# cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
root@ctrl:~# chown $(id -u):$(id -g) $HOME/.kube/config[4] Configure Pod Network with Calico.
root@ctrl:~# wget https://raw.githubusercontent.com/projectcalico/calico/master/manifests/calico.yaml
root@ctrl:~# kubectl apply -f calico.yaml
poddisruptionbudget.policy/calico-kube-controllers created
serviceaccount/calico-kube-controllers created
serviceaccount/calico-node created
serviceaccount/calico-cni-plugin created
configmap/calico-config created
customresourcedefinition.apiextensions.k8s.io/bgpconfigurations.crd.projectcalico.org created
customresourcedefinition.apiextensions.k8s.io/bgpfilters.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/caliconodestatuses.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/ipreservations.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
clusterrole.rbac.authorization.k8s.io/calico-node created
clusterrole.rbac.authorization.k8s.io/calico-cni-plugin created
clusterrolebinding.rbac.authorization.k8s.io/calico-kube-controllers created
clusterrolebinding.rbac.authorization.k8s.io/calico-node created
clusterrolebinding.rbac.authorization.k8s.io/calico-cni-plugin created
daemonset.apps/calico-node created
deployment.apps/calico-kube-controllers created
# show state : OK if STATUS = Ready
root@ctrl:~# kubectl get nodes
NAME STATUS ROLES AGE VERSION
ctrl.srv.world Ready control-plane 4h41m v1.26.6
# show state : OK if all pods are Running
root@ctrl:~# kubectl get pods -A
NAMESPACE NAME READY STATUS RESTARTS AGE
kube-system calico-kube-controllers-56dd5794f-r7fvl 1/1 Running 0 4h36m
kube-system calico-node-89s9h 1/1 Running 0 4h36m
kube-system coredns-787d4945fb-6nn4p 1/1 Running 0 4h41m
kube-system coredns-787d4945fb-qwxb5 1/1 Running 0 4h41m
kube-system etcd-ctrl.srv.world 1/1 Running 0 4h41m
kube-system kube-apiserver-ctrl.srv.world 1/1 Running 0 4h41m
kube-system kube-controller-manager-ctrl.srv.world 1/1 Running 0 4h41m
kube-system kube-proxy-fbfgj 1/1 Running 0 4h41m
kube-system kube-scheduler-ctrl.srv.world 1/1 Running 0 4h41m[5] Join in Kubernetes Cluster which is initialized on Control Plane Node.
The command for joining is just the one [kubeadm join ***] which was shown on the bottom of the results on initial setup of Cluster.
root@snode01:~# kubeadm join 10.0.0.25:6443 --token q1xuoi.v6meo9irmuv9g0y1 \
--discovery-token-ca-cert-hash sha256:1b96782423120e014e212197d34c56b029af1a8db85bf40a6602e19881bc7db1
[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.
# OK if the message above is shown[6] Verify Status on Control Plane Node. That’s Ok if all STATUS are Ready.
root@ctrl:~# kubectl get nodes
NAME STATUS ROLES AGE VERSION
ctrl.srv.world Ready control-plane 4h54m v1.26.6
snode01.srv.world Ready <none> 2m12s v1.26.6
snode02.srv.world Ready <none> 83s v1.26.6
root@ctrl:~# sudo crictl config --set runtime-endpoint=unix:///run/containerd/containerd.sock --set image-endpoint=unix:///run/containerd/containerd.sock
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