How to deploy containerized Flask application to a Kubernetes with Kubeadm on Virtual Machines - Part 1

March 16, 2023

This is the first part of a series of hands-on tutorials for deploying containerized flask application to a Kubernetes with Kubeadm on Virtual Machine.

Series

  1. Part 1
  2. Part 2
  3. Part 3

Overview

In this tutorial we are going a create a Kubernetes cluster with 1 master and 1 worker using Virtual Box.

1. Install VirtualBox

Depending on your OS, the installation will be different. You can refer to the offical link for the installation.

If you are on Ubuntu, you can use the following command to install VirtualBox.

sudo apt update
sudo apt install virtualbox

2. Download Ubuntu ISO

We will be using Ubuntu 22.04 Desktop version. You can download the ISO file from the offical website.

3. Create a Master Virtual Machine

3.1 Create a virtual machine

Let’s first create a master virtual machine.

  1. Click New on VirtualBox.
  2. For Name, type master or or anything you like.
  3. For Type, choose Linux
  4. For Version, choose Ubuntu (64bit) and click Next
  5. For Memory Size, selecte at least 4GB just to make it safer.
  6. From now until File location and size, just choose default value and click Next.
  7. At File location and size, you need to choose at least 20GB. Then click Create.

3.2 Change CPU count

We need to change the CPU count to at least 2 as Kubenetes needs at least 2 CPU per node.

  1. Once the Machine is created, click Settings while selecting the machine.
  2. Go to System > Processor and change the processor count to at least 2 CPU.

3.3 Load ISO file to Storage

We need to load ISO to the drive.

  1. From the Settings of the machine, Go to Storage.
  2. Then click Empty under Controller: IDE.
  3. Then Optical Drive shoud appers on the left side.
  4. Click on the disk icon and a drop down menu will appear.
  5. Select Choose a disk file.. and load the Ubuntu ISO file that you download from the previous section.
  6. Click OK.

3.4 Installation Ubuntu on Virtual Machine

  1. Click Start while selecting the machine.
  2. Select Try or Install Ubuntu after the machine booted up.
  3. Select Install Ubuntu and following the instruction.
  4. Choose Minimal Installation during the Updates and other software to minimize the installation time.
  5. Then click Install Now to install. Do not worry if you see Erase disk and install Ubuntu. It will only erase data from this virtual machine which we don’t have anything on. Then again just follow the instruction.
  6. While at Who are you?, make sure you select Your computer's name that you can recognize. I choose master-vbox and worker-vbox for the master and the worker respectivily.
  7. Pick your username and password you like. Then click Ok and finish the installation.

4. Crate a Worker Virtual Machine.

Just repeated a previous steps to crate a work virtual machine. Take note of the following while creating the worker machine.

  1. Set storage Size to be at least 20GB.
  2. Set memory to be at least 2GB.
  3. Set at least 2 CPU count.
  4. Choose computer name which must be different from the master machine.

5. Setup NAT Networks

We want to use ssh from our physical machine to two virtual machines. So we need to setup the network.

5.2 Create a NAT Network

  1. From VirtualBox, go to File > Preferences.
  2. Then go to Network and click a + network card icon.
  3. Double click on it the network. Set the network you like. Mine is K8sCluster and click OK.

5.3 Connect virtual machines NAT Network

  1. Shutdown both virtual machines.
  2. Then click Settings of the machine.
  3. Click Network
  4. Choose Attached to to NAT Network. Select the NAT network name you created previously. Then click OK. You need to connect both virtual machines to NAT Network.

5.1 Getting IP address of each virtual machine

  1. Turn on both virtual machines.
  2. Go into each virtual machine and open the terminal.

  3. Type in the following command and take note of the IP address.

     ip addr show

    We need IP addresses from both virtual machines.

5.2 Install SSH server

  1. While we are the terminal, install openssh server using the following commmand for the both machines.

     sudo apt install openssh-server

  2. Check the installation with the following command.

     sudo apt install openssh-server

    You should see active (running).

5.3 SSH Port Fowarding

  1. Go to the NAT Network dialog that you just created.
  2. Click Port Fowarding button.

  3. Add the following rules. You need to set the Guest IP as IP addresses that you just recorded from the previous section 5.1.

    Name Protocol Host IP Host Port Guest IP Guest Port
    ssh master TCP 127.0.0.1 2222 10.0.2.15 22
    ssh worker TCP 127.0.0.1 2223 10.0.2.4 22
  4. After you set the values, click OK.

5.3 Test the SSH connection to Virtual Machines

Let’s ssh to our virtual machines.

  1. Make sure you already have ssh client installed on your physical machine. If not, use sudo apt install openssh-client to install.

  2. From your physical machine’s terminal, I use the following command to connect to our master virtual machine.

     ssh -p 2222 aknay@127.0.0.1

The command should be ssh -p <HOST POST> <USERNAME>@127.0.0.1. After successful connection, you should see that your hostname is changed to the hostname that you connected.