Launching Containers from Images

Launching containers from images is a fundamental part of working with Docker. To do this, you use the docker run command, which creates and starts a new container based on a specified image.

The general syntax for this command is:

docker run [OPTIONS] IMAGE [COMMAND]

Some of the most common options include:

• -d: Runs the container in detached mode (in the background);
• -p: Maps ports between your host and the container;
• --name: Assigns a custom name to your container;
• -it: Runs the container interactively, allowing you to use a shell inside the container.

Running the following command starts a new Ubuntu container and provides an interactive shell inside it:

docker run -p 8080:80 nginx

The -p flag maps the container’s internal port 80 to port 8080 on your local machine.

Once the container is running, you can open your browser and go to:

http://localhost:8080

You will see Nginx running at this address. Notice that nothing is running directly on your computer—everything is running inside Docker.

Container Lifecycle: Starting, Stopping, and Removing Containers

Once a container has been started, it goes through a lifecycle that includes several key stages:

• The container starts when you run it from an image;
• It remains running as long as its main process is active;
• You can stop a running container with the docker stop command, which gracefully shuts down the container's process;
• If you want to remove a container entirely, use docker rm, which deletes the container from your system.

Removing a container does not remove the underlying image, so you can always launch a new container from the same image later. Understanding these basic lifecycle commands—starting, stopping, and removing containers—will help you manage your Docker environment efficiently as you build and test applications.