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Summary - Port mapping

Combine port mapping options to publish a web server.

Summary: port mapping

In this group:

  • Container ports don't open to the outside by themselves; they are published with -p host:container.
  • The left side is the host, the right side the container; a host port can be published to only one place.
  • Several -p flags, ranges and /udp are supported.
  • -p 80 and -P pick a random host port; docker port shows the chosen one.
  • 127.0.0.1: opens it only to local access; ports that aren't needed are not published at all.
docker run -d -p 80:80 -p 443:443 nginx
docker run -d -p 127.0.0.1:5432:5432 postgres:16

Practice Web and a local database

Write two commands: start a container named web from nginx in the background, publishing ports 80 and 443 with the same numbers; start a container named db from postgres:16 in the background with POSTGRES_PASSWORD=gizli, publishing 5432 only on 127.0.0.1.

Starter code

terminal
# buraya yaz

Sample solution

terminal
docker run -d --name web -p 80:80 -p 443:443 nginx
docker run -d --name db -e POSTGRES_PASSWORD=gizli -p 127.0.0.1:5432:5432 postgres:16

Expected output

1f2e3d4c5b6a
2e3d4c5b6a7f

Questions and answers

Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.

1 In docker run -p 8080:3000 img, which port must the application listen on inside the container?

  • Both
  • 3000 Correct answer
  • 8080
  • 80

Explanation: The right side is the container port.

2 Publish all EXPOSEd ports.

Question 
docker run -d ____ api:1.0
Answer 
docker run -d -P api:1.0

Explanation: -P picks random ports.

3 Match.

Term Meaning
-p 8080:80 Fixed mapping
-P Random, all EXPOSE
127.0.0.1: Local binding
docker port Show mappings

All lessons in Beginner

1 What is Docker?

  1. What is Docker?
  2. Containers and virtual machines
  3. Images and containers
  4. Docker architecture
  5. Use cases
  6. Summary - What is Docker

2 Installation and first commands

  1. Installing Docker
  2. docker version
  3. docker info
  4. The hello-world container
  5. Docker Desktop
  6. Summary - Installation

3 First container

  1. docker run basics
  2. Running in the background
  3. docker ps
  4. docker stop and rm
  5. docker logs
  6. Summary - First container

4 Dockerfile basics

  1. What is a Dockerfile?
  2. The FROM instruction
  3. The RUN instruction
  4. COPY and ADD
  5. CMD and ENTRYPOINT
  6. Summary - Dockerfile

5 Build and images

  1. docker build
  2. Tagging images
  3. Build context
  4. Layers and cache
  5. .dockerignore
  6. Summary - Build

6 docker run options

  1. Interactive mode
  2. Naming containers
  3. Restart policy
  4. Working directory
  5. Switching users
  6. Summary - docker run

7 Image management

  1. docker images
  2. docker rmi
  3. docker pull
  4. docker push
  5. docker tag
  6. Summary - Image management

8 Port mapping

  1. The port concept
  2. The -p flag
  3. Multiple ports
  4. Random ports
  5. IP binding
  6. Summary - Port mapping

9 Volumes and data

  1. Data persistence
  2. Named volumes
  3. The -v flag
  4. Bind mounts
  5. Volume management
  6. Summary - Volumes

10 Environment variables

  1. The -e flag
  2. The ENV instruction
  3. The ARG instruction
  4. env-file
  5. The WORKDIR instruction
  6. Summary - Environment

11 Project: docker-compose

  1. Compose design
  2. Service definition
  3. Database service
  4. Volume and network
  5. Putting it together - compose

12 Docker Hub and registry

  1. What is Docker Hub?
  2. docker login
  3. Searching images
  4. Official images
  5. Private registry
  6. Summary - Registry

13 Network basics

  1. Network drivers
  2. docker network ls
  3. Bridge network
  4. Container connectivity
  5. Publishing ports
  6. Summary - Network

14 Beginner final

  1. Challenge - Dockerfile
  2. Challenge - Build and run
  3. Challenge - Volume
  4. Challenge - Compose
  5. Challenge - Beginner project