Use cases

Learn common Docker use cases.

Use cases

Docker's most common uses:

Development environment: starting services like PostgreSQL and Redis with one command, without installing them.
CI/CD: running tests every time in a clean, identical environment.
Microservices: deploying each service independently in its own container.
Portable deployment: running the same image on different cloud providers.

docker run -d -e POSTGRES_PASSWORD=gizli -p 5432:5432 postgres:16

Throwaway tools

Docker is also ideal for using a tool once without installing it on the machine. The --rm flag deletes the container automatically when its work is done:

docker run --rm python:3.12 python -c "print(2 ** 10)"
# 1024
docker run --rm -v "$PWD":/app -w /app node:20 npm test

This way different Python or Node versions can be used for different projects without mixing.

Exercise One-off Python

Write the command that runs python -c "print(2 ** 10)" in the python:3.12 image and deletes the container when done.

Test yourself

What is the main benefit of running tests inside a container in a CI pipeline?
- Tests never failing
- A clean, identical environment on every run
- Tests containing less code
- Not needing an internet connection
Show answer

A clean, identical environment on every run — Leftover files from earlier runs or different versions don't affect the result.

Delete the container automatically when it finishes.

docker run ____ python:3.12 python -c "print(1)"

Show answer

docker run --rm python:3.12 python -c "print(1)"

Match the scenarios.

local database

docker run postgres
CI tests

Clean environment
microservice

A container per service
--rm

One-off tool

Next lesson: Summary - What is Docker

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