Kubernetes Worker Node

This includes the steps to implement a worker node using the ubuntu/xenial64 (16.04.6 LTS) image with Vagrant, and VirtualBox on Windows 10.

Initialize the current directory to be a Vagrant environment by creating an initial Vagrantfile. Vagrantfile will be created in the folder.

C:\Vagrant-Lab\Worker-1>vagrant init
A Vagrantfile has been placed in this directory. You are now
ready to vagrant up your first virtual environment! Please read
the comments in the Vagrantfile as well as documentation on vagrantup.com for more information on using Vagrant.

Configure the Vagrantfile with the required settings as below

  • config.vm.box is the different operating systems. More OS can be found here.
  • config.vm.box_version is the OS version. Versions for the OS we use are here.
  • config.vm.network “private_network” creates a second interface and assigns the IP address to the node.
  • config.vm.network “forwarded_port” sets a different port for the SSH. By default it assigns a random value.
  • config.vm.define changes the machine name from default to any value.
  • vb.name changes the VM name on Virtual box from a random value to the configured one.
  • vb.memory updates the memory assigned to the node.
  • vb.cpus updates the cpu assigned to the node

config.vm.box = “ubuntu/xenial64”
config.vm.box_version = “20200407.0.0”
config.vm.network “private_network”, ip: “193.169.1.20”
config.vm.network “forwarded_port”, guest: 22, host: 2260, host_ip: “127.0.0.1”, id: “ssh”
config.vm.define “k8-worker1”
config.vm.provider “virtualbox” do |vb|
vb.name = “vagrant_k8-worker1”
vb.memory = “2048”
vb.cpus = 2

When you run the “vagrant up” command, a new VM machine as “vagrant_k81-worker1” will be created on VirtualBox and powered on automatically. You can ssh to the VM with the configured parameters, ssh 127.0.0.1 port 2260. (Default port is a random value that can be checked with “vagrant ssh-config” command when the VM is running.)

Step 1 : Install Containerd
You can find the details on the Kubernetes site.

## necessary steps to use containerd as CRI runtime ##
$ cat > /etc/modules-load.d/containerd.conf <<EOF
overlay
br_netfilter
EOF
$ modprobe overlay
$ modprobe br_netfilter
$ cat > /etc/sysctl.d/99-kubernetes-cri.conf <<EOF
net.bridge.bridge-nf-call-iptables = 1
net.ipv4.ip_forward = 1
net.bridge.bridge-nf-call-ip6tables = 1
EOF
$ sysctl –system

## Install containerd on Ubuntu ##
$ apt-get update && apt-get install -y apt-transport-https ca-certificates curl software-properties-common
$ curl -fsSL https://download.docker.com/linux/ubuntu/gpg | apt-key add –
add-apt-repository \
“deb [arch=amd64] https://download.docker.com/linux/ubuntu \
$(lsb_release -cs) \
stable”
$ apt-get update && apt-get install -y containerd.io
$ mkdir -p /etc/containerd
$ containerd config default > /etc/containerd/config.toml
$ systemctl restart containerd

Step 2: Install Docker
You can find the details on Dockers site

## Set Up the Repository ##
$ sudo apt-get update
$ sudo apt-get install \
apt-transport-https \
ca-certificates \
curl \
gnupg-agent \
software-properties-common
$ curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add –
$ sudo apt-key fingerprint 0EBFCD88
$ sudo add-apt-repository \
“deb [arch=amd64] https://download.docker.com/linux/ubuntu \
$(lsb_release -cs) \
stable” \

## Install Docker Engine ##
$ sudo apt-get update
$ sudo apt-get install docker-ce docker-ce-cli
$ sudo docker run hello-world

Step 3: Allow regular user to run docker commands
You can add the regular user (vagrant) to the docker user group so that you can run docker commands as vagrant user without sudo privileges.

usermod -aG docker vagrant

Step-4: Install Kubeadm, Kubelet and Kubctl
You can find the details on Kubernetes site

$ 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

Step-5: Kubelet requires swap to be disabled
Some Kubelet/Kubernet versions do not work with Swap enabled on Linux Machines.

swapoff -a
## disable swap permanently ##
sudo sed -i ‘/ swap / s/^\(.*\)$/#\1/g’ /etc/fstab


The worker node is ready with the minimum configurations. 

[email protected]:~$ kubectl get nodes -o wide // shows node status
[email protected]:~$ kubeadm config view // shows the API-server parameters
[email protected]:~$ ps aux | grep apiserver // shows the API-server service

## The units’ status below must be active “(running)” ##
systemctl status kubernetes
systemctl status docker
systemctl status containerd

You can use the vagrant commands to ssh, reload, backup, destoy the node.

C:\Vagrant-Lab\Master-1> vagrant global-status // Shows the global status of all nodes in cluster.
C:\Vagrant-Lab\Master-1> vagrant ssh-config // Shows the ssh config, port
C:\Vagrant-Lab\Master-1> vagrant snapshot save <node-name> <snapshot-name> // Takes snapshot
C:\Vagrant-Lab\Master-1> vagrant reload <node-name> // Reloads the running node
C:\Vagrant-Lab\Master-1> vagrant halt <node-name> // Stops the node
C:\Vagrant-Lab\Master-1> vagrant up <node-name> –provision // Starts the node
C:\Vagrant-Lab\Master-1> vagrant destroy <node-name> // Destroys the node permanently

Step 6: Join to kubeadm Token
In this step, node will join to the master node as worker node. When you run the “kubeadm token create –print-join-command ” on master node, the output is the “kubeadm join …” command for the worker node.

193.169.1.10:6443 shows the API server IP address and the port number.
–dry-run can be used to simulate the command.

[email protected]:~$ kubeadm join 193.169.1.10:6443 –token rehg1k.jo045reyosvrpq6n –discovery-token-ca-cert-hash sha256:9382a71afad8373226258cf0b715d09f2b15b6d24b5b77734457c97194c6fdce

Series Navigation<< Kubernetes Single Master NodeKubernetes Node Deployment Problems >>