In this tutorial, we will cover how to manage Docker image versions and tags. Docker tags are mutable references to an image ID. We can use tags to differentiate between different versions of our Docker images.
After completing this tutorial, you will be able to:
- Create Docker tags
- Update Docker tags
- Manage different versions of Docker images using tags
Prerequisites:
- Basic understanding of Docker
- Docker installed on your machine
A Docker image tag is a label that we can assign to an image, so we can have different versions of the same image. To create, update, or manage a Docker image tag, we use the docker command followed by tag.
Creating a Docker Tag
To create a Docker tag, we need to have a Docker image to tag. The syntax is: docker tag SOURCE_IMAGE[:TAG] TARGET_IMAGE[:TAG]
Updating a Docker Tag
If we want to update a Docker tag, we simply need to create a new image and assign it the same tag. Docker will automatically update the tag to refer to the newest image.
Managing Different Versions
We can manage different versions of our Docker images by assigning each version a unique tag.
Example 1: Creating a Docker Tag
# Create a Docker tag
docker tag my_image my_image:v1.0
In the above example, we create a tag v1.0 for the Docker image named my_image.
Example 2: Updating a Docker Tag
# Update a Docker tag
docker tag my_new_image my_image:v1.0
In this example, we update the v1.0 tag to refer to a new image my_new_image.
Example 3: Managing Different Versions
# Create multiple Docker tags for different versions
docker tag my_image my_image:v1.0
docker tag my_image my_image:v1.1
docker tag my_image my_image:v1.2
In this example, we create three different versions (v1.0, v1.1, v1.2) for the Docker image my_image.
Today, we've learned how to create, update, and manage Docker image versions using tags. We've seen how to create a tag, update an existing tag, and use tags to manage different versions of a Docker image.
For further learning, consider exploring:
- How to use Dockerfile to build Docker images
- How to use Docker Compose to manage multiple containers
Exercise 1:
Create a Docker image and assign it a tag. Then, create a new Docker image and update the tag to refer to the new image.
Solution:
# Create a Docker image and tag
docker tag my_image my_image:v1.0
# Update the Docker tag
docker tag my_new_image my_image:v1.0
Exercise 2:
Create three different versions for a Docker image using tags.
Solution:
# Create three Docker tags for different versions
docker tag my_image my_image:v1.0
docker tag my_image my_image:v1.1
docker tag my_image my_image:v1.2
For further practice, consider creating a Dockerfile to build your Docker images and use Docker Compose to manage multiple containers.