Tags Matter

In a previous lesson, we mentioned that an image name can include an optional tag. In this lesson, we will discuss tags in a bit more detail and learn why they are important.

Earlier, we saw that image names include a name and a tag. As a quick reminder, an image name is:

<repository_name>/<name>:<tag>
  • tag is optional; when missing, it is considered to be latest by default
  • repository_name can be a registry DNS or the name of a registry in the Docker Hub

While your images aren’t published to a registry, you don’t need to include a registry name. So, your image name is:

<name>:<tag>

The latest tag

In my demonstrations I didn’t include a tag; therefore the default latest tag was used. For instance, the actual image name was hello:latest when I ran the following command:

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