Naming and Tagging Images

Introduction

Docker Tag is a label assigned to a Docker image that allows users to identify and manage the image effectively. The tag provides a meaningful and recognizable name for the image, making it easier to understand its purpose and contents. The Docker Tag Command creates a new tag for a Docker image. By default, Docker will use the latest tag if none is specified, and it's possible to create multiple tags for a single image. Understanding and utilizing Docker tags is crucial for effective image management and deployment.

Naming Docker Image

Naming a Docker image is an important step in the process of building and managing Docker images. A well-named Docker image can make it easier to understand the purpose and contents of the image, as well as to differentiate it from other images.

Overall, choosing a clear and descriptive name for your Docker images is important to help make them easy to understand and manage.

Docker Tag Command

The Docker tag command creates a new tag for a Docker image. This allows you to give a specific image a meaningful and easily recognizable name, which can be used to identify and manage the image.

The syntax for the Docker tag command is as follows: docker tag IMAGE_ID REPOSITORY: TAG

For Example if you want to tag an image with the ID "abc123" as "myapp: latest", you would run the following command:

Copy code docker tag abc123 myapp: latest

Use-Cases of Docker Tags

Docker tags are used to identify specific versions or variants of Docker images. They can be used in many different ways, including:

• Version control: Docker tags can be used to track the version history of an image and roll back to a previous version if necessary.

• Environment separation: Different tags can be used to identify images that are intended for use in different environments, such as development, staging, and production.

• Collaboration: Docker tags can be used to share images with other developers or deploy them to a registry for use in continuous integration/continuous delivery (CI/CD) pipelines.

Docker Tags to Explicitly Tag an Image

To explicitly tag an image in Docker, you can use the docker tag command. This command allows you to create a new tag for an existing image in your local Docker image repository.

Here's an example of how you can use the docker tag command: docker tag <image> <repository>:<tag>

Example: docker tag myapp myapp: latest

What Happens When We don't Specify Image Tags?

If you don't specify a tag when you run a Docker command that involves an image, Docker will use the latest tag by default. For example, if you run the Docker run command to start a container from an image and don't specify a tag, Docker will use the latest tag to find the image.

For example: docker run myapp

This command will start a container from the myapp image with the latest tag.

Images with Multiple Tags

It's possible to create multiple tags for a single Docker image. This can be useful in many different scenarios.

To create multiple tags for an image, you can use the docker tag command multiple times, specifying a different tag for each instance.

Examples

Tag an image referenced by ID

To tag an image in Docker using its ID, you can use the docker tag command and specify the ID of the image in the image parameter.

Example: docker tag 123456789abc myapp:latest

Tag an image referenced by Name and Tag

To tag an image that is referenced by name and tag, you can use the docker tag command and specify the name and tag of the source image in the image parameter and the name and tag of the destination image in the : parameter.

Example: docker tag myapp: latest myapp:v1.0

Tag an image for a private repository

Tag the image using the docker tag command and specify the full repository name, including the registry hostname, in the parameter.

Example: docker tag myapp <registry-hostname>/myapp:latest