Install kubernetes with kubeadm V2

Kubernetes
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Kubeadm is a tool that helps you bootstrap a simple Kubernetes cluster and simplifies the deployment process.

Parts of the Kubernetes series

192.168.1.41  kubernetes01 # master node
192.168.1.42  kubernetes02 # frontend node
192.168.1.43  kubernetes03 # worker node
192.168.1.44  kubernetes04 # worker node
192.168.1.45  kubernetes05 # worker node

# hardware requirement
4 CPU
16G RAM

Enable cgroupV2

sudo dnf install -y grubby
sudo grubby \
  --update-kernel=ALL \
  --args="systemd.unified_cgroup_hierarchy=1"

cat << EOF >> /etc/systemd/system.conf
DefaultCPUAccounting=yes
DefaultIOAccounting=yes
DefaultIPAccounting=yes
DefaultBlockIOAccounting=yes
EOF

init 6

Configure date time and selinux

timedatectl set-timezone Europe/Budapest

dnf install -y vim net-tools chrony ntpstat
timedatectl set-ntp true
systemctl enable chronyd --now

systemctl stop firewalld
systemctl mask firewalld

setenforce 0
sed -i 's/=\(enforcing\|permissive\)/=disabled/g' /etc/sysconfig/selinux
sed -i 's/=\(enforcing\|permissive\)/=disabled/g' /etc/selinux/config

echo "net.ipv6.conf.all.disable_ipv6 = 1" >> /etc/sysctl.conf
echo "net.ipv6.conf.default.disable_ipv6 = 1" >> /etc/sysctl.conf
sysctl -p

echo "centos.mydomain.lan" > /etc/hostname
hostnamectl set-hostname centos.mydomain.lan

ifconfig | grep inet | grep -v inet6 | cut -d" " -f10 | sed "s|$|   `hostname -s` `hostname -f`|" >> /etc/hosts
sed -i "s|::1|#::1|" /etc/hosts

Install containerd

dnf install -y epel-release
dnf install -y device-mapper-persistent-data lvm2 iproute-tc
dnf config-manager --add-repo https://download.docker.com/linux/centos/docker-ce.repo
dnf install -y containerd.io

## Configure containerd
sudo mkdir -p /etc/containerd
sudo containerd config default > /etc/containerd/config.toml

Configuuration

To use the systemd cgroup driver in /etc/containerd/config.toml with runc, set

nano /etc/containerd/config.toml
...
          [plugins."io.containerd.grpc.v1.cri".containerd.runtimes.runc.options]
            SystemdCgroup = true

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

sudo modprobe overlay
sudo modprobe br_netfilter

cat <<EOF | sudo tee /etc/sysctl.d/99-kubernetes-cri.conf
net.bridge.bridge-nf-call-iptables  = 1
net.ipv4.ip_forward                 = 1
net.bridge.bridge-nf-call-ip6tables = 1
EOF

sysctl --system

As you can see we dose n ot siabled the swap:

# show swap is on
$ swapon --show
NAME      TYPE      SIZE USED PRIO
/dev/sda1 partition   2G   0B   -2

# check for type cgroup2
$ mount -l|grep cgroup
cgroup2 on /sys/fs/cgroup type cgroup2 (rw,nosuid,nodev,noexec,relatime,seclabel,nsdelegate)

# check for cpu controller
$ cat /sys/fs/cgroup/cgroup.subtree_control
cpu io memory pids

Install kubeadm

cat << EOF >> /etc/yum.repos.d/kubernetes.repo
[kubernetes]
name=Kubernetes
baseurl=https://packages.cloud.google.com/yum/repos/kubernetes-el7-x86_64
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
EOF

sudo dnf -y install kubelet kubeadm kubectl --disableexcludes=kubernetes

# Start containerd
systemctl enable --now containerd

echo "runtime-endpoint: unix:///run/containerd/containerd.sock" > /etc/crictl.yaml
crictl ps

Change runtime in kubeadm config:

# add the following flags to KUBELET_KUBEADM_ARGS variable
cat << EOF > /etc/sysconfig/kubelet
KUBELET_EXTRA_ARGS="--node-ip=192.168.1.41 --container-runtime=remote --container-runtime-endpoint=/run/containerd/containerd.sock --cgroup-driver=systemd --fail-swap-on=false"
EOF

sudo systemctl enable --now kubelet
sudo systemctl status kubelet

kubeadm config images pull

Init master

sudo kubeadm init \
--pod-network-cidr=10.244.0.0/16 \
--apiserver-advertise-address=192.168.1.41 \
--cri-socket=unix:///run/containerd/containerd.sock \
--ignore-preflight-errors="Swap"



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


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

Join workers to cluster

kubeadm join 192.168.100.10:6443 --token XXXXXXXX \
    --discovery-token-ca-cert-hash sha256:XXXXXXXX

yum install -y https://harbottle.gitlab.io/harbottle-main/7/x86_64/harbottle-main-release.rpm
yum install -y kubectx helm