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Summary - What is Docker

Combine Docker's core concepts to write a container definition.

Summary: what Docker is

In this group:

  • Docker runs an application with its dependencies inside a container.
  • A container shares the host kernel; it is lighter and faster than a VM, and its isolation comes from namespaces and cgroups.
  • An image is a read-only template; a container is its running instance and carries its own writable layer.
  • The CLI sends commands to the daemon; the daemon pulls images from the registry.
  • One-off tools can be run with --rm.
docker pull nginx
docker run -d --name web --memory 256m nginx
docker run --rm alpine echo merhaba

Practice All together

Write three commands: pull the alpine image; start a container from it that runs echo merhaba and is deleted when done; finally start a container named web from the nginx image running in the background.

Starter code

terminal
# buraya yaz

Sample solution

terminal
docker pull alpine
docker run --rm alpine echo merhaba
docker run -d --name web nginx

Expected output

Status: Downloaded newer image for alpine:latest
merhaba
5c6d7e8f9a01

Questions and answers

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

1 What happens to a file created inside a container when the container is removed?

  • It is deleted together with the writable layer Correct answer
  • It is saved into the image
  • It is uploaded to Docker Hub
  • It is moved to the host desktop

Explanation: Persistent data needs a volume.

2 Start the container in the background.

Question 
docker run ____ --name web nginx
Answer 
docker run -d --name web nginx

Explanation: -d (detached) releases the terminal.

3 Match.

Term Meaning
image Template
container Instance
dockerd Daemon
--rm Automatic removal

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