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Install Kubernetes (k8s) v1.22 Highly Available Clusters on CentOS 7

1. Preparation

1.1 KVMs

8 KVMs

Hostname vCPUs Memory Swap IP OS sudoer
master01.k8s 2 2G 0 192.168.10.191 CentOS 7 echo
master02.k8s 2 2G 0 192.168.10.192 CentOS 7 echo
master03.k8s 2 2G 0 192.168.10.193 CentOS 7 echo
minion01.k8s 2 8G 0 192.168.10.101 CentOS 7 echo
minion02.k8s 2 8G 0 192.168.10.102 CentOS 7 echo
minion03.k8s 2 8G 0 192.168.10.103 CentOS 7 echo
slb01.k8s 2 2G 0 192.168.10.201 CentOS 7 echo
slb02.k8s 2 2G 0 192.168.10.202 CentOS 7 echo
cluster.k8s - - - 192.168.10.200 - -

NOTE: 192.168.10.200 is a virtual (HA) IP which points to slb01 or slb02.

1.2 Install Ansible on Host machine

# Install ansible on host machine
sudo yum install ansible

1.3 Password free configuration

cat <<EOF | sudo tee -a /etc/ansible/hosts
[k8s]
master01.k8s
master02.k8s
master03.k8s
minion01.k8s
minion02.k8s
minion03.k8s

[k8s-master]
master01.k8s
master02.k8s
master03.k8s

[k8s-minion]
minion01.k8s
minion02.k8s
minion03.k8s
EOF

# Have a test 
ansible k8s --ask-pass -u echo -m shell -a 'echo ok'

# Password free for login
ansible k8s --ask-pass -u echo -m file -a "path=.ssh state=directory mode=700"
ansible k8s --ask-pass -u echo -m copy -a "src=~/.ssh/id_rsa.pub dest=.ssh/authorized_keys mode=600"

# Password free for sudo
ansible k8s --ask-pass -u echo -b -m shell -a "echo 'echo ALL=(ALL) NOPASSWD: ALL' >> /etc/sudoers"

# Now we can have a test as below
ansible k8s -u echo -m shell -a 'echo ok'

1.4 DNS via hosts file

cat <<EOF > /tmp/add-hosts.sh
cat <<EEE >> /etc/hosts 
192.168.10.191 master01.k8s
192.168.10.192 master02.k8s
192.168.10.193 master03.k8s

192.168.10.101 minion01.k8s
192.168.10.102 minion02.k8s
192.168.10.103 minion03.k8s

192.168.10.201 slb01.k8s
192.168.10.202 slb02.k8s

# A virtual IP which points slb01 or slb02
192.168.10.200 cluster.k8s
EEE
EOF

ansible k8s -u echo -b -m script -a "/tmp/add-hosts.sh"

2. Basic configurations for servers

2.1 Firewall configuration (required ports)

NOTE: eth0, 192.168.10.0/24 may be changed according to your own environment.

cat <<EOF > /tmp/required-ports.sh
# Possible other interfaces instead of eth0
firewall-cmd --permanent --zone=trusted --add-interface=eth0
# Your internal network
firewall-cmd --permanent --zone=trusted --add-source=192.168.10.0/24
# Flannel
firewall-cmd --permanent --zone=trusted --add-interface=flannel.1
# POD cidr
firewall-cmd --permanent --zone=trusted --add-source=10.244.0.0/16
# Service cidr
firewall-cmd --permanent --zone=trusted --add-source=10.96.0.0/16

firewall-cmd --permanent --add-port=6443/tcp
firewall-cmd --permanent --add-port=2379-2380/tcp
firewall-cmd --permanent --add-port=10250-10252/tcp
firewall-cmd --permanent --add-port=30000-32767/tcp
firewall-cmd --reload
EOF

ansible k8s -u echo -b -m script -a '/tmp/required-ports.sh'

2.2 Set SELinux in permissive mode (effectively disabling it)

cat <<EOF > /tmp/set-selinux.sh
sudo setenforce 0
sudo sed -i 's/^SELINUX=enforcing$/SELINUX=permissive/' /etc/selinux/config
EOF

ansible k8s -u echo -b -m script -a '/tmp/set-selinux.sh

2.3 Disable swap

You MUST disable swap in order for the kubelet to work properly.

ansible k8s -u echo -b -m shell -a 'swapoff -a'
ansible k8s -u echo -b -m shell -a 'sed -i -e "s:/dev/mapper/centos-swap:#/dev/mapper/centos-swap:" /etc/fstab'

2.4 Verify the MAC address and product_uuid are unique for every node

ansible k8s -u echo -m shell -a '/usr/sbin/ip link | grep link/ether'

ansible k8s -u echo -b -m shell -a 'cat /sys/class/dmi/id/product_uuid'

2.5 Letting iptables see bridged traffic

# Make sure that the br_netfilter module is loaded
ansible k8s -u echo -m shell -a '/usr/sbin/lsmod | grep br_netfilter'

# To load it explicitly
ansible k8s -u echo -b -m shell -a 'modprobe br_netfilter'

# Ensure net.bridge.bridge-nf-call-iptables is set to 1 in your sysctl config
cat <<EEE > /tmp/ensure-bridge-nf.sh
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
EEE

ansible k8s -u echo -b -m script -a '/tmp/ensure-bridge-nf.sh'

2.6 Sysctl for KVM

cat <<EEE > /tmp/set-sysctl.sh
cat <<EOF | sudo tee /etc/sysctl.d/kvm.conf
net.ipv4.conf.default.rp_filter=0
net.ipv4.conf.all.rp_filter=0
net.ipv4.conf.all.proxy_arp = 1
EOF
sudo sysctl --system
EEE

ansible k8s -u echo -b -m script -a '/tmp/set-sysctl.sh'

3. Install docker-ce as the container runtime

3.1 Install container-selinux

ansible k8s -u echo -m shell -a \
'sudo yum --enablerepo=extras install -y container-selinux'

3.2 Check docker-ce version

yum --showduplicates list docker-ce

3.3 Install docker-ce

NOTE: Use your mirror of dockerhub

cat <<EEE > /tmp/install-docker.sh
# Install Docker CE 18.06 from Docker's CentOS repositories:

## Install prerequisites.
yum -y install yum-utils device-mapper-persistent-data lvm2

## Add docker repository.
yum-config-manager \
    --add-repo \
    https://download.docker.com/linux/centos/docker-ce.repo

## Install docker.
yum -y install docker-ce-18.06.1.ce-3.el7
systemctl enable docker

# Setup daemon.
mkdir -p /etc/docker/
cat > /etc/docker/daemon.json <<EOF
{
  # NOTE: Use your mirror of dockerhub
  "registry-mirrors": ["https://z7sy3gme.mirror.aliyuncs.com"],
  "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

mkdir -p /etc/systemd/system/docker.service.d

# Restart docker.
systemctl daemon-reload
systemctl restart docker
EEE

ansible k8s -u echo -b -m script -a '/tmp/install-docker.sh'

4. Install HAProxy + Keepalived as the Load Balancer

See Install Haproxy v1.8 and Keepalived on CentOS 7 for the installation.

Config HAProxy, add a listen for k8sapi

cat << EEE > /tmp/k8sapi-proxy.sh
cat << EOF | sudo tee -a /etc/opt/rh/rh-haproxy18/haproxy/haproxy.cfg

listen k8sapi
    bind *:6443
    mode tcp
    balance roundrobin
    option  tcp-check
    server  master01 master01.k8s:6443 check
    server  master02 master02.k8s:6443 check
    server  master03 master03.k8s:6443 check
EOF
EEE

ansible slb -u echo -b -m script -a '/tmp/k8sapi-proxy.sh'

Restart HAProxy

ansible slb -u echo -b -m shell -a "systemctl restart rh-haproxy18-haproxy"

5. Install kubeadm, kubelet and kubectl

NOTE: Use your own baseurl and gpgkey

cat <<EEE > /tmp/install-kubeadm.sh 
cat <<EOF | sudo tee /etc/yum.repos.d/kubernetes.repo
[kubernetes]
name=Kubernetes
baseurl=https://mirrors.aliyun.com/kubernetes/yum/repos/kubernetes-el7-x86_64
enabled=1
gpgcheck=1
repo_gpgcheck=1
gpgkey=https://mirrors.aliyun.com/kubernetes/yum/doc/yum-key.gpg https://mirrors.aliyun.com/kubernetes/yum/doc/rpm-package-key.gpg

exclude=kubelet kubeadm kubectl
EOF

yum install -y kubelet kubeadm kubectl --disableexcludes=kubernetes
systemctl enable --now kubelet
EEE

ansible k8s -u echo -b -m script -a '/tmp/install-kubeadm.sh'

Check kubeadm version

ansible k8s -u echo -m shell -a 'kubeadm version | awk -F, "{print \$3}"' 

6. Creating HA clusters with kubeadm

Ping cluster.k8s

ping cluster.k8s -c 5

6.1 Init cluster on master01.k8s

For flannel pod network (see 6.3), the argument --pod-network-cidr=10.244.0.0/16 should be provided.

sudo kubeadm init --control-plane-endpoint "cluster.k8s:6443" --upload-certs --pod-network-cidr=10.244.0.0/16

Output:

[init] Using Kubernetes version: v1.22.1
......

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 the control-plane node running the following command on each as root:

  kubeadm join cluster.k8s:6443 --token aswx9l.y6nmyeh3u3urvmgt \
    --discovery-token-ca-cert-hash sha256:246676b26c3215a836ea4b55d61437edd62cc7a3a6fceca8c4cb40070fad9d88 \
    --control-plane --certificate-key 5f6b55ca0aef4b76322dec1076313e0cb0ba19e1c3f1254cf68af3d3c8fabad6

Please note that the certificate-key gives access to cluster sensitive data, keep it secret!
As a safeguard, uploaded-certs will be deleted in two hours; If necessary, you can use
"kubeadm init phase upload-certs --upload-certs" to reload certs afterward.

Then you can join any number of worker nodes by running the following on each as root:

kubeadm join cluster.k8s:6443 --token aswx9l.y6nmyeh3u3urvmgt \
    --discovery-token-ca-cert-hash sha256:246676b26c3215a836ea4b55d61437edd62cc7a3a6fceca8c4cb40070fad9d88 

6.2 Create $HOME/.kube/config on master01.k8s

  mkdir -p $HOME/.kube
  sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
  sudo chown $(id -u):$(id -g) $HOME/.kube/config

6.3 Deploy a pod network (flannel) to the cluster

On master01.k8s

kubectl apply -f https://raw.githubusercontent.com/coreos/flannel/master/Documentation/kube-flannel.yml

6.4 Join the control-plane node

On master02.k8s, master03.k8s

# e.g.
sudo kubeadm join cluster.k8s:6443 --token aswx9l.y6nmyeh3u3urvmgt \
--discovery-token-ca-cert-hash sha256:246676b26c3215a836ea4b55d61437edd62cc7a3a6fceca8c4cb40070fad9d88 \
--control-plane --certificate-key 5f6b55ca0aef4b76322dec1076313e0cb0ba19e1c3f1254cf68af3d3c8fabad6

Output:

[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'
......
This node has joined the cluster and a new control plane instance was created:

* Certificate signing request was sent to apiserver and approval was received.
* The Kubelet was informed of the new secure connection details.
* Control plane (master) label and taint were applied to the new node.
* The Kubernetes control plane instances scaled up.
* A new etcd member was added to the local/stacked etcd cluster.

To start administering your cluster from this node, 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

Run 'kubectl get nodes' to see this node join the cluster.

6.5 Join worker nodes

On minion01.k8s, minion02.k8s, minion03.k8s

# e.g.
sudo kubeadm join cluster.k8s:6443 --token aswx9l.y6nmyeh3u3urvmgt \
    --discovery-token-ca-cert-hash sha256:246676b26c3215a836ea4b55d61437edd62cc7a3a6fceca8c4cb40070fad9d88 

Output:

[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.

6.6 Check the cluster

On master01.k8s. Check the nodes

kubectl get nodes

Output:

NAME           STATUS   ROLES                  AGE     VERSION
master01.k8s   Ready    control-plane,master   3h52m   v1.22.1
master02.k8s   Ready    control-plane,master   28m     v1.22.1
master03.k8s   Ready    control-plane,master   4m35s   v1.22.1
minion01.k8s   Ready    <none>                 39s     v1.22.1
minion02.k8s   Ready    <none>                 75s     v1.22.1
minion03.k8s   Ready    <none>                 2m51s   v1.22.1

Check the pods

kubectl get pod --all-namespaces

Output:

NAMESPACE     NAME                                   READY   STATUS    RESTARTS        AGE
kube-system   coredns-78fcd69978-79fxq               1/1     Running   0               33m
kube-system   coredns-78fcd69978-x65cm               1/1     Running   0               33m
kube-system   etcd-master01.k8s                      1/1     Running   2               33m
kube-system   etcd-master02.k8s                      1/1     Running   7               30m
kube-system   etcd-master03.k8s                      1/1     Running   0               6m24s
kube-system   kube-apiserver-master01.k8s            1/1     Running   3               33m
kube-system   kube-apiserver-master02.k8s            1/1     Running   7               30m
kube-system   kube-apiserver-master03.k8s            1/1     Running   3               30m
kube-system   kube-controller-manager-master01.k8s   1/1     Running   1 (7m19s ago)   33m
kube-system   kube-controller-manager-master02.k8s   1/1     Running   1               30m
kube-system   kube-controller-manager-master03.k8s   1/1     Running   1               30m
kube-system   kube-flannel-ds-88wbk                  1/1     Running   0               4m19s
kube-system   kube-flannel-ds-fznsw                  1/1     Running   0               4m56s
kube-system   kube-flannel-ds-kln22                  1/1     Running   0               3m39s
kube-system   kube-flannel-ds-n2hfp                  1/1     Running   0               18m
kube-system   kube-flannel-ds-n2qc4                  1/1     Running   0               18m
kube-system   kube-flannel-ds-qhh5q                  1/1     Running   0               18m
kube-system   kube-proxy-9hdxz                       1/1     Running   1               30m
kube-system   kube-proxy-cptvt                       1/1     Running   0               3m39s
kube-system   kube-proxy-hw4wm                       1/1     Running   0               4m18s
kube-system   kube-proxy-rcj7c                       1/1     Running   0               4m56s
kube-system   kube-proxy-tbq7p                       1/1     Running   1               32m
kube-system   kube-proxy-vmrqc                       1/1     Running   0               33m
kube-system   kube-scheduler-master01.k8s            1/1     Running   5 (7m19s ago)   33m
kube-system   kube-scheduler-master02.k8s            1/1     Running   3               30m
kube-system   kube-scheduler-master03.k8s            1/1     Running   2               30m

Cluster Info

kubectl cluster-info

Output:

Kubernetes control plane is running at https://cluster.k8s:6443
CoreDNS is running at https://cluster.k8s:6443/api/v1/namespaces/kube-system/services/kube-dns:dns/proxy

To further debug and diagnose cluster problems, use 'kubectl cluster-info dump'.

Reference


Last update: 2021-12-02
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