It Works on My Laptop

The situation

The Code Nexus Assist service that passed every check on the developer workspace won't start in staging. Nobody changed the code. What differs is everything the code assumes: which versions of the libraries are installed, which files are lying around, what the entry command is. Maya's laptop has an environment nobody wrote down, and staging has a different one. Kabelo's proposal is to stop describing the environment in a wiki and write it as a Dockerfile, so the same image runs the same way everywhere.

What you'll learn

• Docker practice: images and containers, layers and build cache, build context and .dockerignore, ordering a Dockerfile, pinning inputs, non-root execution, avoiding embedded secrets and checking local build reproducibility.

Who you work with

• 

  Kabelo Mokoena

  Platform and DevOps Engineer

• 

  Maya Chen

  Senior AI Engineer · Your mentor

Scenes

1. 1.Green on the laptop, red in staging
2. 2.Read it the way the builder does
3. 3.Write the environment down
4. 4.It builds. It doesn't run.
5. 5.Docker basics check

What you leave with

You fixed dependency ordering, pinned the fixture versions, limited the build context and ran the service as its non-root user. The simulator's two builds match; tags, transitive packages, build tools, hashes and runtime settings still need control for real reproducibility. Logs then identified the wrong script path and missing package.