C# / .NETDevOpsMisc
DevOps
Setting up a Kubernetes cluster
Alexandru Puiu
Alexandru Puiu
December 04, 2019
2 min

Table Of Contents

01
Install CentOS Stream
02
Install CentOS Stream
03
Installing Kubernetes on CentOS 8 Stream
04
Deploy a Kubernetes Cluster

I decided to go with CentOS Stream as the base OS it’s the most familiar to me, but there are many great options. This cluster is not going to be hardened or production-ready, in this case, I needed a quick one set to test some distributed algorithms and to give my cluster of 10 Raspberry Pi’s something to do.

Install CentOS Stream

Download the image from https://www.centos.org/download/

Burn it to a DL-DVD if you have any around.. or create a bootable USB

Creating a bootable USB with CentOS 8 Stream

If you’re using Linus as your main OS, then dd is the most straightforward way. Just use dd and target the flash drive, but make sure to reference the main device and not a partition.

dd if=CentOS-6.5-x86_64-bin-DVD1.iso of=/dev/sdz

Device names on windows are not as pleasant to work with, so while dd is an option on Windows, I find Win32 Disk Imager a quicker option. Several more options can be found here https://wiki.centos.org/HowTos/InstallFromUSBkey

Transfer the image to the USB drive using Win32 Disk Imager

Just select the ISO and Device, and hit Write. Takes a few minutes, and it’s ready for install.

win32 disk imager

How to fix a USB drive after Win32 Disk Imager

Win32 Disk Imager needs exclusive access to the USB drive. If anything interrupts the process, or it can’t get lock the device, it’s going to mess it up a bit, and Disk Management in Windows 10 can’t fix that. Instead, we’ll need to use DiskPart.

Run CMD as Administrator and run the following in sequence. This will take some time, as it formats the drive.

diskpart
list disk
(make note of the number assigned to your USB drive)
select disk X
clean
create partition primary
active
format fs=fat32 label=""
assign
exit

Install CentOS Stream

Boot off of the DVD or USB drive, and install as normal.

Since this is going to be the kube master, give it a hostname that will help you identify it later.

Installing Docker on CentOS 8 Stream With Yum

Update Yum Package Database

sudo yum check-update

Install the dependencies

sudo yum install -y yum-utils device-mapper-persistent-data lvm2

Add the Docker Repository

sudo yum-config-manager --add-repo https://download.docker.com/linux/centos/docker-ce.repo

Install the Docker Engine

  • As of the writing of this, containerd fails to install automatically, and you need to specify the version. Just run this:
dnf install https://download.docker.com/linux/centos/7/x86_64/stable/Packages/containerd.io-1.2.6-3.3.el7.x86_64.rpm

Now you can install the rest

sudo yum install docker-ce docker-ce-cli

Start docker

sudo systemctl start docker

Optionally, you can start a test container to make sure everything works

sudo docker run hello-world

Done. Repeat the procedure on every node you want in the cluster

Installing Kubernetes on CentOS 8 Stream

Add the kubernetes repo

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 kubelet, kubeadm, and kubectl

sudo yum install -y kubelet kubeadm kubectl
systemctl enable kubelet
systemctl start kubelet

Update the hosts file on each node to know about each other

Open necessary ports on the master node

sudo firewall-cmd --permanent --add-port=6443/tcp
sudo firewall-cmd --permanent --add-port=2379-2380/tcp
sudo firewall-cmd --permanent --add-port=10250/tcp
sudo firewall-cmd --permanent --add-port=10251/tcp
sudo firewall-cmd --permanent --add-port=10252/tcp
sudo firewall-cmd --permanent --add-port=10255/tcp

And on each worker node

sudo firewall-cmd --permanent --add-port=10251/tcp
sudo firewall-cmd --permanent --add-port=10255/tcp

Create a new config file under /etc/sysctl.d/ (ex: master_node.conf) and enter the following. This makes sure that packets are processed by iptables during port forwarding

net.bridge.bridge-nf-call-ip6tables = 1
net.bridge.bridge-nf-call-iptables = 1

Reload config

sysctl --system

Disable SWAP

sudo sed -i '/swap/d' /etc/fstab
sudo swapoff -a

Deploy a Kubernetes Cluster

Setup Pod Network

Install flannel

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

Create a Cluster with kubeadm

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

Check the status of the cluster

sudo kubectl get pods --all-namespaces

Manage the cluster 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

Join Worker Node to Cluster

kubeadm join --discovery-token cfgrty.1234567890jyrfgd --discovery-token-ca-cert-hash sha256:1234..cdef 1.2.3.4:6443

Verify Nodes from Master

sudo kubectl get nodes

Tags

devopskubernetes
Alexandru Puiu

Alexandru Puiu

Engineer / Security Architect

Systems Engineering advocate, Software Engineer, Security Architect / Researcher, SQL/NoSQL DBA, and Certified Scrum Master with a passion for Distributed Systems, AI and IoT..

Expertise

.NET
RavenDB
Kubernetes

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