11 Ship a change

11 / 13

Goal

Change the app to answer Hello, Docker!, and get the running app container serving it on port 3000.

A container is created from an image once. Rebuilding the image produces a new image; the container keeps running the old one until you replace it.

That's why deploys are "build a new image, start new containers from it, remove the old ones" — and why the curl in the middle of the solution still says the old thing.

Try it

Change the message, rebuild, check, replace, check again.

Go to the terminal

Hint

Edit server.js, docker build -t myapp ., then replace the container: docker rm -f app and docker run -d --name app -p 3000:3000 myapp.

Show a solution

nano server.js
# In the editor: const http = require("http") · http.createServer((req, res) => res.end("Hello, Docker!")).listen(3000)
docker build -t myapp .
curl localhost:3000
docker rm -f app
docker run -d --name app -p 3000:3000 myapp
curl localhost:3000

This interactive environment needs JavaScript. Everything you need to read is on this page, and the solution works the same way for real.

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