Running Ubuntu in Docker (for Practice)

This webbook covers many command-line tools and concepts. The easiest way to follow along and practice is to use a consistent environment. We’ll use a Docker container running Ubuntu Linux for this purpose. This allows you to experiment without affecting your host operating system.

Prerequisites:

Steps:

  1. Start an Interactive Ubuntu Container:

    Open a terminal (Command Prompt or PowerShell on Windows, Terminal on macOS/Linux) and run the following command:

    docker run -it --rm ubuntu:22.04 bash

    Explanation:

    • docker run: This command creates and starts a new container.
    • -it: This is a combination of two options:
      • -i (--interactive): Keeps STDIN open, allowing you to interact with the container.
      • -t (--tty): Allocates a pseudo-TTY, which gives you a terminal interface.
    • --rm: This option automatically removes the container when you exit it. This is very convenient for temporary testing environments, as it prevents the buildup of stopped containers.
    • ubuntu:22.04: This specifies the Docker image to use. We’re using the official Ubuntu 22.04 image from Docker Hub.
    • bash: This specifies the command to run inside the container when it starts. In this case, we’re starting a Bash shell, giving you a command-line prompt within the Ubuntu container.

    After running this command, you’ll be inside the Ubuntu container’s shell. Your prompt will likely change to something like root@<container_id>:/#.

  2. Update and Prepare the Container (Optional, but Recommended):

    Inside the container, run the following commands:

    apt update  # Update the package list
apt upgrade -y # Upgrade the installed packages
apt install -y --no-install-recommends unminimize nano g++ telnet python3 python3-pip net-tools iputils-ping tcpdump

    Explanation:

    • apt update: Updates the list of available packages. Always run this before installing new packages.
    • apt upgrade -y: Upgrades all installed packages to their latest versions.
    • apt install -y --no-install-recommends ...: Installs the necessary tools for the webbook exercises:
    • --no-install-recommends: Installs only essential dependencies, keeping the image size down.
    • unminimize: Restores some packages that are removed in the minimal Ubuntu base image.
      • nano: A simple text editor.
      • g++: The GNU C++ compiler.
      • telnet: A basic network utility (useful for testing network connectivity – though often replaced by netcat or nmap).
      • python3: The Python 3 interpreter.
      • python3-pip: The package installer for Python.
      • net-tools: Provides ifconfig command.
      • iputils-ping: Provides the ping command.
      • tcpdump: A network packet analyzer.
    • -y: Automatically answers “yes” to any prompts during installation.

  3. Open Additional Terminals (Optional):

If you need to run multiple commands simultaneously or have multiple shells open to the same container, you can use docker exec.

  • First, find the container ID or name. While inside the container, you can usually see the container ID in the prompt. You can also run docker ps in a separate terminal (on your host machine) to list running containers:

    docker ps
# CONTAINER ID   IMAGE          COMMAND    CREATED       STATUS       PORTS     NAMES
# a1b2c3d4e5f6   ubuntu:22.04   "bash"     2 minutes ago Up 2 minutes             my_ubuntu

  • Then, use docker exec to open a new shell in the running container:

      docker exec -it a1b2c3d4e5f6 bash  # Use the container ID or name
  # OR
  docker exec -it my_ubuntu bash

    This command opens a new interactive Bash shell (-it bash) inside the running container (a1b2c3d4e5f6 or my_ubuntu). You’ll have two separate terminals connected to the same container.

  1. Exiting the Container:

    To exit the container, simply type exit at the container’s shell prompt. Because we used the --rm option when starting the container, the container will be automatically deleted when you exit.

Windows (Alternative Approach)

If you’re using Windows and prefer not to use Docker Desktop, you can use Windows Subsystem for Linux (WSL) to run a Linux distribution (like Ubuntu) directly on Windows. This provides a native Linux environment without the overhead of a virtual machine.

  • Run Linux containers on Windows (using Hyper-V containers – this is still within a container).
  • Install WSL (using WSL 2 – this runs a full Linux kernel). This is generally the recommended approach for development on Windows.

Once WSL is set up, you can install the necessary tools (Git, Docker, etc.) within the Linux distribution, just as you would on a native Linux system.