kubernetes Installation on centos7/RHEL77/Ubuntu 16.04+

by Anish

Posted on Wednesday July 11, 2018

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Introduction

In this section we will learn how to install kubernetes in centos7/rhel7/ubuntu like system

Prerequisite Machines

  1. Ubuntu 16.04+
  2. CentOS 7
  3. RHEL 7
  4. 2 GB or more of RAM per machine (any less will leave little room for your apps)

Setup Environment


| Master          | Minion Cluster    |
|-------------    |----------------   |
| kube-master     | kube-minion-1     |

Steps Required to Install Kubenetes-master and Kubenetes-minion


| Requirement                                        | Kubenetes-master  | Kubenetes-minion  |
|------------------------------------------------    |------------------ |------------------ |
| Disable system swap and SELinux                    | Y                 | Y                 |
| remove any swap entry from /etc/fstab              | Y                 | Y                 |
| net.bridge.bridge-nf-call-iptables is set to 1     | Y                 | Y                 |
| Install Docker & enable on restart             | Y                 | Y                 |
| Install kubeadm                                    | Y                 | Y                 |
| Install kubelet                                    | Y                 | N                 |
| Install kubectl                                    | Y                 | N                 |
| Configure docker cgroupsfs                         | Y                 | N                 |
| Creating Network Addons (flannel/Calico)           | Y                 | N                 |

Step-1 Disable system swap run swapoff -a this will immediately disable swap and remove any swap entry from /etc/fstab

Step-2 Disable SE Linux by setenforce 0

Step-4 You should ensure net.bridge.bridge-nf-call-iptables is set to 1 in your sysctl config

cat <<EOF >  /etc/sysctl.d/k8s.conf
net.bridge.bridge-nf-call-ip6tables = 1
net.bridge.bridge-nf-call-iptables = 1
EOF
sysctl --system

Step-5 Install Docker & enable on restart CentOS7&RHEL7

yum -y update
yum install -y docker 

Step-5.1 Install Docker & enable on restart Ubuntu

apt-get update 
apt-get install -y docker.io

start and enable Docker Service and check docker service is running

systemctl start docker
systemctl enable docker
systemctl status docker

Step-6 kubernetes Installation starts here

You will install these packages on all of your machines:

  1. kubeadm: the command to bootstrap the cluster.
  2. kubelet: the component that runs on all of the machines in your cluster and does things like starting pods and containers.
  3. kubectl: the command line util to talk to your cluster.

kubernetes installation on centos7/rhel7

Setting up Kubernetes yum repository on centos6.x/rhel7.x

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

Install Kubernetes in centos7/rhel7

yum install -y kubelet kubeadm kubectl

kubernetes installation on Ubuntu Setting up Kubernetes apt repository for Ubuntu

apt-get install -y apt-transport-https curl
apt-get install -y docker.io

Add kube Repo


curl -s https://packages.cloud.google.com/apt/doc/apt-key.gpg | apt-key add -
cat <<EOF >/etc/apt/sources.list.d/kubernetes.list
deb http://apt.kubernetes.io/ kubernetes-xenial main
EOF
apt-get update

Install Kubernetes in ubuntu

apt-get install -y kubelet kubeadm kubectl

Enable & start kublet

systemctl enable kubelet  
systemctl start kubelet

Step-7 Verify that your Docker cgroup driver matches the kubelet config: (kube-master node)

docker info | grep -i cgroup
Cgroup Driver: cgroupfs

Configuration for cgroup drive is right in /etc/systemd/system/kubelet.service.d/10-kubeadm.conf

[Service]
Environment="KUBELET_CGROUP_ARGS=--cgroup-driver=cgroupfs"

Step-8 reload daemon and restart kubelet: (kube-master node)

systemctl daemon-reload
systemctl restart kubelet

Step-9 Flush Reset Kubernetes component (This will wipeout all the cluster config if exist any do not run this after the config create)

kubeadm reset -f 

Step-10 kubernetes Network Addon setups starts here

  • For flannel to work correctly, --pod-network-cidr=10.244.0.0/16 has to be passed to kubeadm init.
  • For Calico to work correctly, --pod-network-cidr=192.168.0.0/16 has to be passed to kubeadm init.

*Creating flannel Networks *

Note apiserver-advertise-address is the IP of the kube-master

kubeadm init --service-cidr 10.96.0.0/12 --kubernetes-version v1.11.0 --pod-network-cidr 10.244.0.0/16 --apiserver-advertise-address 192.168.1.130

You should get information back on initiating commands as a normal user, as well as the network that you need to deploy as well as how to join worker nodes to the cluster.

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

Step-11 Join the Cluster (kube-minnion)

kubeadm join 192.168.1.130:6443 --token 5m8qxr.46rpadiwt8fcka0v --discovery-token-ca-cert-hash sha256:b05a0b8849a57432247c06200864f5ce99d40ffdcae965293c0026204ef33da4

Step-12 Run kubectl get nodes on the master to see this node join the cluster. It will few seconds to get your cluster in ready state

root@kube-master:kubectl get nodes
NAME          STATUS    ROLES     AGE       VERSION
kube-master   Ready     master    2m        v1.11.0
kube-minion   Ready     <none>    47s       v1.11.0

Step-12 Apply flannel Addons

kubectl apply -f https://raw.githubusercontent.com/coreos/flannel/v0.10.0/Documentation/kube-flannel.yml

You will get output like this

clusterrole.rbac.authorization.k8s.io/flannel created
clusterrolebinding.rbac.authorization.k8s.io/flannel created
serviceaccount/flannel created
configmap/kube-flannel-cfg created
daemonset.extensions/kube-flannel-ds created

Step-13 Enable and restart kubelet engine

systemctl restart kubelet
systemctl status kubelet

Verification

Verify the Cluster Information

root@kube-master: kubectl cluster-info 
Kubernetes master is running at https://192.168.1.132:6443
KubeDNS is running at https://192.168.1.132:6443/api/v1/namespaces/kube-system/services/kube-dns:dns/proxy

Verify the Services

root@kube-master:kubectl get services -n kube-system
NAME                   TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)         AGE
kube-dns               ClusterIP   10.96.0.10      <none>        53/UDP,53/TCP   2m

Create Tokens

[root@kube-master ~]kubeadm token create 
I0710 04:08:37.149017    8685 feature_gate.go:230] feature gates: &{map[]}
d49l0d.mheeem1dkrw3n436

All Service Operational


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