DOCKER · Networking · 8 min

Publish a port on localhost only

Expose a practice web server without binding it to every interface.

Not completed

Your task

Run opsrung-web:practice as opsrung-web and map host port 8088 to container port 8080. Bind only to 127.0.0.1. If 8088 is occupied, choose another free local port.

What you’re aiming for

The named container is running the image you built.
Container port 8080 is mapped to host port 8088, or your chosen free port.
The host binding is 127.0.0.1.

1. Prepare your practice folder

Use a running Docker engine in Linux container mode. The setup commands below use a Bash-compatible shell: Git Bash on Windows, or Bash on Linux/macOS.

Create a new, empty folder for this exercise. If that name already exists, choose another new name. Continue only after you’re inside the new folder.

NEW PRACTICE FOLDER

mkdir opsrung-docker-local-port && cd opsrung-docker-local-port

Run these setup commands in that folder:

SETUP — RUN ONCE

cat > Dockerfile <<'DOCKERFILE'
FROM alpine:3.22
RUN apk add --no-cache busybox-extras
WORKDIR /site
RUN printf 'Practice server\n' > index.html
USER 65534:65534
CMD ["httpd","-f","-p","8080","-h","/site"]
DOCKERFILE
docker build -t opsrung-web:practice .

Docker may download the official Alpine image and, for the web task, its HTTP package. If an example container name already exists, use a different name consistently. If port 8088 is occupied, choose another free local port.

2. Try the task

Work toward the goal above. Start by inspecting the files or resources, then use a hint if you need one.

Hint 1

The Dockerfile from setup creates a small web server listening on port 8080.

Hint 2

A port mapping can include a host address before the host port.

Hint 3

Use -p 127.0.0.1:8088:8080, substituting your chosen host port if needed.

3. Review your result

Use these commands to look at your result and compare it with the goals. The website does not run or verify them.

REVIEW IN YOUR TERMINAL

docker port opsrung-web
curl http://127.0.0.1:8088

What you should see

docker port opsrung-web shows container port 8080 mapped to 127.0.0.1:8088, or your chosen free host port.
curl to that local address prints Practice server.

If your result differs: A binding of 0.0.0.0 does not meet this task. Use 127.0.0.1 explicitly, and use your chosen host port in both the mapping and curl command.

Compare with one possible solution

ONE POSSIBLE SOLUTION

docker run -d --name opsrung-web -p 127.0.0.1:8088:8080 --read-only --cap-drop ALL --security-opt no-new-privileges opsrung-web:practice
docker port opsrung-web

Other approaches are fine if you reach the same goal. Opening this solution does not mark the exercise complete.

Clean up this exercise

Only remove the example resources you created. Volume cleanup deletes that exercise’s saved sample data. Keep anything you need.

OPTIONAL CLEANUP

docker stop opsrung-web
docker rm opsrung-web
docker image rm opsrung-web:practice

Finished this exercise?

You decide when you’re done. Your choice is saved in this browser, and you can change it later.