350-901 Question #84: Real Exam Question with Answer & Explanation

Question

Refer to the exhibit. The command `docker build --tag=friendlyhello .` is run to build a docker image from the given Dockerfile, requirements.txt, and app.py. Then the command `docker run -p 4000:80 friendlyhello` is executed to run the application. Which URL is entered in the web browser to see the content served by the application?

Options

• Ahttp://localhost:4000
• Bhttp://localhost:80
• Chttp://127.0.0.1:80
• Dhttp://0.0.0.0:80

Explanation

The docker run -p 4000:80 command maps port 4000 on the host machine to port 80 inside the Docker container, making the container's service accessible from the host's localhost on port 4000.

Common mistakes.

• B. Port 80 on localhost is not mapped to the container's application unless explicitly configured otherwise, and usually host port 80 would require root privileges.
• C. 127.0.0.1 is the loopback address for localhost, but port 80 refers to the container's internal port, which is not directly accessible from the host without port mapping.
• D. 0.0.0.0 is a wildcard address used within the container to listen on all available network interfaces, but it is not a URL to be entered in a web browser from the host.

Concept tested. Docker port mapping and application access

Reference. https://docs.docker.com/engine/reference/commandline/run/#publish-or-expose-port--p---expose

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