How to use Docker tags to manage image versions efficiently

Learn how to use Docker tags to manage different versions of your Docker images and ensure consistent and organized development workflows. This guide covers best practices for tagging, updating, and maintaining Docker images.

Prerequisites

Before you start:

• You must have Docker installed in your development environment. Get Docker If you haven't already.
• A sample application that you want to convert to Docker. If you want, you can use This example on GitHub.

Tagging Docker Images

A Docker tag is a label that points to a specific image within a repository. By default, Docker uses the tag latest Label if no label is specified. However, if you are developing your application and improving it over several versions, you may want to add more explicit labels. These labels are useful for distinguishing between different versions or states of an image.

Let's say you have a Python project: a Flask application for inventory management with all the necessary files in the project directory:

project-dir/
├── app.py
├── Dockerfile
├── requirements.txt

You can tag an image when you create it as follows:

$ docker build -t image_name:tag_name

Now we are going to build the inventory-app image and tag it:

$ docker build -t inventory-app:1.0.0 .

Here:

• inventory-app is the name of the repository or the name of the image.
• 1.0.0 is the label for this specific build of the image.

You can run the docker images Command to view the newly created image with the specified tag:

$ docker images
REPOSITORY      TAG           IMAGE ID       CREATED        SIZE
inventory-app   1.0.0         32784c60a992   6 minutes ago   146MB

You can also tag an existing image as shown:

$ docker tag inventory-app:1.0.0 inventory-app:latest

Here, we are tagging an existing image. inventory-app:1.0.0 as inventory-app:latestYou'll see that we have two inventory app images with different tags and the same image ID:

$ docker images
REPOSITORY      TAG           IMAGE ID       CREATED        SIZE
inventory-app   1.0.0         32784c60a992   6 minutes ago   146MB
inventory-app   latest        32784c60a992   5 minutes ago   146MB

How to submit tagged images to a repository

To share your Docker images, you can push them to a Docker repository (such as DockerHub). You can sign up for a free DockerHub account, log in, and push images. You must first log in to DockerHub:

You will be prompted for your username and password. Once authentication is successful, you can send the image tagged with the docker push domain.

Make sure your repository name matches your Docker Hub username or organization. If your Docker Hub username is user and you want to submit version 1.0.1 of the image, tag your image as user/inventory-app:1.0.1:

$ docker tag user/inventory-app:1.0.1
$ docker push user/inventory-app:1.0.1

When you need to use a specific version of an image, you can get it using the tag:

$ docker pull user/inventory-app:1.0.1

Best practices for tagging Docker images

Below are some best practices to follow when tagging Docker images:

• Use semantic versioning:Follow a version scheme like MAJOR.MINOR.PATCH (1.0.0, 1.0.1). This helps to identify the importance of changes.
• Avoid the use of latest For production: Use explicit version tags for production deployments.
• Automate labeling in CI/CD pipelines:Integrate Docker tagging into your CI/CD pipelines to ensure automatic and consistent version control.
• Including metadata in tags:If it makes sense, add build numbers, commit hashes, or dates to the tags.

By following these practices when using Docker tags, you can maintain a clean, organized, and versioned set of Docker images.

Additional Resources

Below are a couple of resources you may find helpful:

twitter.com/balawc27″ rel=”noopener”>Bala Priya C. Bala is a technical developer and writer from India. She enjoys working at the intersection of mathematics, programming, data science, and content creation. Her areas of interest and expertise include DevOps, data science, and natural language processing. She enjoys reading, writing, programming, and drinking coffee! Currently, she is working on learning and sharing her knowledge with the developer community by creating tutorials, how-to guides, opinion pieces, and more. Bala also creates interesting resource overviews and coding tutorials.