Your First Container

Estimated time: 15 minutes

You will run a real web server in a container, view it running, then stop and remove it. This is the basic lifecycle you will repeat constantly.

Before You Build Your Own Image

Building your own image (for your Next.js app) comes in the next section. Before that, it helps to practice the basic commands using an existing public image — so the commands feel familiar once you start building your own.

We will use nginx, a popular web server, as this practice image.

Running a Container

Start nginx

Terminal


docker run -d -p 8080:80 --name my-first-container nginx

Here is what each part means:

docker run — create and start a container from an image
-d — run in the background (“detached”), so your terminal stays free
-p 8080:80 — connect port 8080 on your machine to port 80 inside the container (this is how your browser reaches it)
--name my-first-container — give the container a name you can reference later
nginx — the image to use (Docker pulls it from Docker Hub automatically if you do not have it yet)

Open It in a Browser

Go to http://localhost:8080 . You should see the nginx welcome page.

This page is being served from inside a container, not from a program installed on your machine. If you stop the container, the page disappears.

Viewing Running Containers

To see what containers are currently running:

Terminal


docker ps

Output looks like this:


CONTAINER ID   IMAGE     COMMAND                  CREATED         STATUS         PORTS                  NAMES
a1b2c3d4e5f6   nginx     "/docker-entrypoint..."  2 minutes ago   Up 2 minutes   0.0.0.0:8080->80/tcp   my-first-container

The real output is wide and often wraps in a normal terminal — that is expected, not an error. The columns that matter most for now are STATUS (is it running?) and NAMES (which container is it?).

docker ps only shows running containers. To see all containers, including stopped ones, add -a: docker ps -a

Stopping the Container

Stopping a container ends the running process, but does not delete it.

Terminal


docker stop my-first-container

Run docker ps -a again — the container is still listed, just no longer running.

Removing the Container

Once you are done with a container, you can remove it completely:

Terminal


docker rm my-first-container

docker rm deletes the container permanently. Any data that only existed inside that container is gone. The image itself (nginx) is untouched — you can create a new container from it anytime.

The Lifecycle So Far


docker run   →  container created and running
docker ps    →  see it running
docker stop  →  container stopped, still exists
docker rm    →  container deleted completely

Hands-on Task

Do this yourself before moving on:

Run an nginx container named practice-container on port 9090 instead of 8080.
Confirm it works by opening http://localhost:9090 in your browser.
Check it is listed with docker ps.
Stop it, confirm with docker ps -a that it still exists but is stopped.
Remove it.

Quick Check

Can you run a container and reach it in your browser?
Do you understand the difference between stop and rm?
Can you explain what -p 8080:80 does?

Next → Essential Commands