Setting Up SSH Connection Between Two Ubuntu Containers in Docker

This project focuses on setting up an SSH (Secure Shell) connection between two Ubuntu containers running within Docker

SSH is a protocol that allows encrypted communication between systems, ensuring data confidentiality, integrity, and authenticity. By configuring one container as an SSH server and the other as an SSH client, this setup demonstrates how secure communication between two Docker containers can be achieved using password based authentication

Objective:

The objective of this project is to demonstrate how to configure and establish a secure SSH connection between two Ubuntu containers in Docker, enabling encrypted communication using password based authentication

Requirements:

• Docker Desktop installed and running on the host machine to enable the creation and management of Docker containers

• Basic Command Line Knowledge: familiarity with terminal commands for Docker and Linux systems

• Internet Access

Implementation Process

Step 1:

Pull the latest Ubuntu image from Docker Hub using the following command:

docker pull ubuntu

Create a new folder for the project using the following command:

mkdir ubuntu-containers

Step 2:

Create and name the first container ‘container1’ running it in an interactive mode:

docker run -it --name container1 ubuntu

Install the OpenSSH server package in container1. This enables the container to function as an SSH server, allowing it to accept incoming SSH connections. The package includes all necessary components for running an SSH server:

apt-get update 
apt-get install openssh-server

Step 3:

Edit the SSH configuration file to allow connections. To do this, install the command-line text editor ‘nano’ using the following command:

apt-get install nano

Use the following command to open and edit the SSH configuration file:

nano /etc/ssh/sshd_config

In the configuration file, locate Authentication section. Uncomment the ‘PermitRootLogin’ by removing the ‘#” character at beginning of the line. Then, delete ‘prohibit- password’ and replace it with ‘yes’. Save and exit the file

Start the SSH service in container1:

Step 4:

Create and run the second container ‘container2’ in interactive mode using the following command:

docker run -it --name container2 ubuntu

In container2, install the OpenSSH client package. This allows the container to function as an SSH client and initiate outgoing SSH connections. The package contains the necessary tools required to connect to an SSH server:

apt-get update
apt-get install openssh-client

Exit container2 and start container1 using the following command:

docker start container1

The following command will allow to execute Bash commands inside container1:

docker exec -it container1 bash

Retrieve the root user’s password hash in container1 using the following command:

cat /etc/shadow | grep root

Configure the root password inside container1 to enable password based SSH authentication using the following command:

passwd root

To connect to container1 from container2 via SSH, retrieve container1’s IP address using the following command:

docker inspect container1 | grep IPAddress

Step 5:

Start container2 using the following command:

 docker start container2

Run the following command to execute Bash commands inside container2:

docker exec -it container2 bash

Connect to container1 via SSH using its IP address by running the following command inside container2:

ssh root@172.17.0.2

Answer ‘yes’ when prompted, then authenticate using the root user password previously set. A successful SSH connection is established afterwards

Key Takeaways:

• Improved Security: by setting up an SSH connection between the two containers, a secure and encrypted communication channel is established. This ensures confidentiality, integrity, and authenticity of the transmitted data, helping protect the application from unauthorized access and potential breaches

• Simplified Infrastructure Management: Docker simplifies the process of managing and deploying containers, reducing complexity and time required to handle application infrastructure. This ease of management supports faster development, testing, and deployment cycles

• Team Collaboration: this project setup allows multiple team members to work on the same application simultaneously. Each member can use a separate container that communicates securely with others, improving productivity and collaboration. Team members can work independently while sharing their work securely and efficiently

• Scalability: containers are lightweight and can be scaled up or down quickly to match changing application demands. Docker enables rapid provisioning of containers to handle increased load and scaling down when demand drops, optimizing resource usage and reducing cost

• Portability: Docker containers are highly portable, enabling easy movement between different environments and cloud platforms. This reduces the risk of dependency conflicts and simplifies deployment across various stages of development and production

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