Installing Kubernetes with the Flannel Network Plugin on Ubuntu 22.04

install-kubernetes-flannel-centos7.md

Install Prerequisites on ALL (Worker and Master) Nodes

UPDATED FOR UBUNTU 22.04

Update all packages and install CRI-O container runtime

sudo apt update
sudo apt upgrade -y


# Configure persistent loading of modules
sudo tee /etc/modules-load.d/k8s.conf <<EOF
overlay
br_netfilter
EOF

# Ensure you load modules
sudo modprobe overlay
sudo modprobe br_netfilter

# Set up required sysctl params
sudo tee /etc/sysctl.d/kubernetes.conf<<EOF
net.bridge.bridge-nf-call-ip6tables = 1
net.bridge.bridge-nf-call-iptables = 1
net.ipv4.ip_forward = 1
EOF

# Reload sysctl
sudo sysctl --system

# Add Cri-o repo
OS="xUbuntu_22.04"
VERSION=1.26
echo "deb https://download.opensuse.org/repositories/devel:/kubic:/libcontainers:/stable/$OS/ /" | sudo tee -a /etc/apt/sources.list.d/devel:kubic:libcontainers:stable.list
echo "deb http://download.opensuse.org/repositories/devel:/kubic:/libcontainers:/stable:/cri-o:/$VERSION/$OS/ /" | sudo tee -a /etc/apt/sources.list.d/devel:kubic:libcontainers:stable:cri-o:$VERSION.list
curl -L https://download.opensuse.org/repositories/devel:kubic:libcontainers:stable:cri-o:$VERSION/$OS/Release.key | sudo apt-key add -
curl -L https://download.opensuse.org/repositories/devel:/kubic:/libcontainers:/stable/$OS/Release.key | sudo apt-key add -

# Install CRI-O
sudo apt update
sudo apt install cri-o cri-o-runc

# Start and enable Service
sudo systemctl daemon-reload
sudo systemctl restart crio
sudo systemctl enable crio
systemctl status crio

Remove swap:

sudo swapoff -a
sudo sed -i 's|.*swap.*||' /etc/fstab

Install kubelet and kubeadm on ALL (Worker and Master) Nodes

sudo apt-get install -y apt-transport-https ca-certificates curl
sudo curl -fsSLo /etc/apt/keyrings/kubernetes-archive-keyring.gpg https://packages.cloud.google.com/apt/doc/apt-key.gpg
echo "deb [signed-by=/etc/apt/keyrings/kubernetes-archive-keyring.gpg] https://apt.kubernetes.io/ kubernetes-xenial main" | sudo tee /etc/apt/sources.list.d/kubernetes.list

sudo apt-get update
sudo apt-get install -y kubelet kubeadm kubectl
sudo apt-mark hold kubelet kubeadm kubectl
sudo kubeadm config images pull --cri-socket unix://var/run/crio/crio.sock

Configure Kubernetes Master

On the master node, we want to run:

sudo kubeadm init --pod-network-cidr=10.244.0.0/16

The --pod-network-cidr=10.244.0.0/16 option is a requirement for Flannel - don't change that network address!

Save the command it gives you to join nodes in the cluster, but we don't want to do that just yet. You should see a message like

You can now join any number of machines by running the following on each node as root:

  kubeadm join --token <token> <IP>:6443

Start the cluster as a normal user. This part, I realized, was pretty important as it doesn't like to play well when you do it as root.

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

Install Flannel for the Pod Network (On Master Node)

We need to install the pod network before the cluster can come up. As such we want to install the latest yaml file that flannel provides. Most installations will use the following:

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

At this point, give it about a minute, and have a look at the status of the cluster. run kubectl get pods --all-namespaces and see what it comes back with. If everything shows running, then you're in business!

Add Worker Nodes to the Cluster

Upto this point, we haven't really touched the worker nodes (other than installing the prerequisites), but now you can join the worker nodes by running the command that was given to us when we created the cluster

sudo kubeadm join --token <token> <ip>:6443

We'll see more services spinning up on other services:

kubectl get pods --all-namespaces

NAMESPACE     NAME                                                    READY     STATUS    RESTARTS   AGE
...
kube-system   kube-flannel-ds-fldtn                                   0/2       Pending   0          3s
...
kube-system   kube-proxy-c8s32                                        0/1       Pending   0          3s

And to confirm, when we do a kubectl get nodes, we should see something like:

NAME                            STATUS    AGE       VERSION
server1                         Ready     46m       v1.7.0
server2                         Ready     3m        v1.7.0
server3                         Ready     2m        v1.7.0

Running Workloads on the Master Node

By default, no workloads will run on the master node. You usually want this in a production environment. In my case, since I'm using it for development and testing, I want to allow containers to run on the master node as well. This is done by a process called "tainting" the host.

On the master, we can run the command kubectl taint nodes --all node-role.kubernetes.io/master- and allow the master to run workloads as well.