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Kubernetes cluster example with Ubuntu

You can easily build a cluster using kubeadm and kubectl on Ubuntu 18.04.

Perform these steps on all the machines that will be part of your cluster.

First, have Docker installed:

sudo apt-get install -y docker.io

Then install the kubeadm toolbox:

sudo apt-get update && sudo apt-get install -y apt-transport-https curl
curl -s https://packages.cloud.google.com/apt/doc/apt-key.gpg | sudo apt-key add -
cat <<EOF | sudo tee /etc/apt/sources.list.d/kubernetes.list
deb https://apt.kubernetes.io/ kubernetes-xenial main
EOF
sudo apt-get update
sudo apt-get install -y kubelet kubeadm kubectl
sudo apt-mark hold kubelet kubeadm kubectl

Swap must be disabled for kubelet to run:

sudo swapoff -a

Only on the machine designated as master node:

Select the IP address to broadcast the Kubernetes API. With ifconfig you can check the IPs of the network interfaces on your master node (with a public IP you can expose the cluster to the internet).

Then run the following line substituting <IP-address> with your IP.

sudo kubeadm init --apiserver-advertise-address=<IP-address>

When it finishes executing, you will find a result similar to this:

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

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/

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

kubeadm join <IP-address>:6443 --token 29am26.3fw2znktwbbff0we \
    --discovery-token-ca-cert-hash sha256:eb32f7f58ae6907f26ed5c075ecd4ef6756d832b6c358fd4b2f408e52d18a369

Now kubeadm set up a cluster with just the master node. Run those 3 instructions to copy the admin.conf file, to connect kubectl to the new cluster.

Then you can checkout your nodes with:

kubectl get nodes

NAME          STATUS     ROLES    AGE     VERSION
master-node   NotReady   master   7m25s   v1.17.0

The node will stay in the NotReady status until you apply Pod Networking. With Weave Net run:

kubectl apply -f "https://cloud.weave.works/k8s/net?k8s-version=$(kubectl version | base64 | tr -d '\n')"

After a minute the node will be Ready. Check the Weave Net addon to know more.

Now you're ready to let other machines join. Use the join command kubeadm printed earlier on them.

kubeadm join <IP-address>:6443 --token 29am26.3fw2znktwbbff0we \
    --discovery-token-ca-cert-hash sha256:eb32f7f58ae6907f26ed5c075ecd4ef6756d832b6c358fd4b2f408e52d18a369

After a node joined give it time to get in the Ready status, then you can check that everything is running with: kubectl get all -A.

Now you have a running cluster with a master node and one or more worker nodes.

Before deploying OpenWhisk, you have to set up Dynamic Volume Provision, as the technical requirements specify. For example, you can dynamically provision NFS persistent volumes, setting up an nfs server, a client provisioner and a storage class. Now you're ready to deploy openwhisk with Helm.

Weave Network Plugin Troubleshooting

ensure that weave has launched by running kubectl get pods -A and looking for a pod named similarly to weave-net-##### - if the status is Running you're good. if you see CrashLoopBackOff perform the following steps:

  1. Get logs kubectl logs -n kube-system weave-net-m4j75 -c weave
  2. if you see an error like this: Network 10.32.0.0/12 overlaps with existing route 10.33.82.0/23 on host that means you need to choose a different network for kubernetes to assign to itself
  3. return your cluster to a default state sudo kubeadm reset and hit y when it asks if you're certain you want to do this
  4. Choose a new private network and init the cluster like this: sudo kubeadm init --pod-network-cidr=192.168.128.0/17 --apiserver-advertise-address=<IP ADDRESS>
  5. tell the weave plugin to use these new values as listed in the configuration options kubectl apply -f "https://cloud.weave.works/k8s/net?k8s-version=$(kubectl version | base64 | tr -d '\n')&env.IPALLOC_RANGE=192.168.128.0/17"
  6. it should now show as Running under status