Install Kubernetes on CentOS 7 with kubeadm

• Install kubeadm

Turn OFF: Fail on Swap Setting

k8s must allow a development cluster to swap. There is simply not enough memory on development machines like laptops.

kubeadm initialization

Add the --ignore-preflight-errors Swap flag to the kubeadm init command. This command should be run only once.

#! /bin/bash
#
# Download and start kubeadm.
# ===================================

# Set HTTP Proxies and pull-down kubeadm images.
export http_proxy="http://one.proxy.att.com:8080"
export https_proxy="http://one.proxy.att.com:8080"
kubeadm config images pull

# Add missing "flannel" Docker image.
docker pull quay.io/coreos/flannel:v0.10.0-amd64

# Clear HTTP Proxies and start it.
# (kubeadm and kublet can't find each other over a proxy.)
unset http_proxy
unset https_proxy
kubeadm init --ignore-preflight-errors Swap

kubelet configuration

The kubelet must have its flag --fail-swap-on=false to allow the cluster to swap.

$ sudo vi /etc/systemd/system/kubelet.service.d/10-kubeadm.conf

# Allow Swap ON for local development machine!
ExecStart=/usr/bin/kubelet $KUBELET_KUBECONFIG_ARGS $KUBELET_CONFIG_ARGS $KUBELET_KUBEADM_ARGS $KUBELET_EXTRA_ARGS --fail-swap-on=false

# Refresh configs and start kubelet (when it is NOT the master).
$ sudo systemctl daemon-reload
$ sudo systemctl start kubelet

Preparing kubctl to Use the Cluster

kubctl manages both master and nodes as a non-root user. There are a few things needed to make this work.

Users must set NO_PROXY to the Cluster IP address

The master and all nodes need this step before kubectl can work.

Find the cluster IP address in the $HOME/.kube/config file. Add the IP address (without port) to the uppercase NO_PROXY env. variable.

Cluster IP in config YAML

The IP address apears after the server: YAML label.

server: https://10.0.2.15:6443

Choose and apply a CNI pod network

The master and all nodes need this step.

Every node must apply a CNI pod network type to use. This README installs the flannel RPM to use it.

kubectl apply -f https://raw.githubusercontent.com/coreos/flannel/bc79dd1505b0c8681ece4de4c0d86c5cd2643275/Documentation/kube-flannel.yml

Single-Machine Cluster Allows Nodes on Master

By default, the cluster will not schedule pods on the master for security reasons. Run the kubectl below to schedule pods on the master and make a single-machine Kubernetes cluster for development.

kubectl taint nodes --all node-role.kubernetes.io/master-