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docker tag

Learn to give an image a new tag with docker tag.

docker tag

docker tag SOURCE TARGET adds a new name to an existing image. No copy is made; both names point at the same image ID. It is used to repoint moving tags when releasing a version:

docker tag api:1.3.0 api:1.3
docker tag api:1.3.0 api:latest
docker tag api:1.3.0 registry.ornek.com:5000/api:1.3.0

Save and load

To move an image to another machine without a registry, it is saved to a tar archive. save/load carry the image with its layers and tags:

docker save -o api.tar api:1.3.0
scp api.tar sunucu:/tmp/
ssh sunucu docker load -i /tmp/api.tar
# Loaded image: api:1.3.0

Practice Version tags and moving

Write the commands: add the tags api:2.1 and api:latest to the api:2.1.0 image (two commands); then save api:2.1.0 to the file api.tar; finally list the images of the api repository.

Starter code

terminal
# buraya yaz

Sample solution

terminal
docker tag api:2.1.0 api:2.1
docker tag api:2.1.0 api:latest
docker save -o api.tar api:2.1.0
docker images api

Expected output

REPOSITORY   TAG      IMAGE ID       CREATED       SIZE
api          2.1      8c9d0e1f2a3b   2 hours ago   162MB
api          2.1.0    8c9d0e1f2a3b   2 hours ago   162MB
api          latest   8c9d0e1f2a3b   2 hours ago   162MB

Questions and answers

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

1 How does disk usage change after docker tag?

  • It decreases
  • It grows with the number of tags
  • It doesn't change; a new name is added to the same image Correct answer
  • It doubles

Explanation: A tag is only a pointer.

2 Save the image to a tar file.

Question 
docker ____ -o api.tar api:1.3.0
Answer 
docker save -o api.tar api:1.3.0

Explanation: save outputs the image, export a container's file system.

3 Match.

Term Meaning
docker tag New name
docker save Write the image to tar
docker load Read an image from tar
host:5000/ Private registry

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