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This article shows you how to carry out the practice of naming Docker images. The content is concise and easy to understand. It will definitely brighten your eyes. I hope you can get something through the detailed introduction of this article.

We have learned to build our own images. The next question is how to use mirroring on multiple Docker Host.

Here are several ways to do this:

Use the same Dockerfile to build the image on other host.

Upload the image to a public Registry (such as Docker Hub), and download the image directly using Host.

Set up a private Registry for local Host use.

The first method is nothing special. There has been a lot of discussion before. We will discuss how to use public and private Registry to distribute images.

Name the mirror

No matter how you save and distribute the image, you must first name the image.

We already have a name for the image when we execute the docker build command, such as before:

Docker build-t ubuntu-with-vi

The ubuntu-with-vi here is the name of the image. You can view the information of the image through dock images.

Notice here that ubuntu-with-vi corresponds to REPOSITORY, and there is also a TAG called latest.

In fact, the name of a particular image consists of two parts: repository and tag.

[image name] = [repository]: [tag]

If tag is not specified when docker build is executed, the default value of latest is used. The effect is equivalent to:

Docker build-t ubuntu-with-vi:latest

Tag is often used to describe the version information of an image, such as a httpd image

Of course, tag can be any string, such as ubuntu image

Be careful, latest tag.

Don't be misled by latest tag. Latest doesn't really have any special meaning. When the mirror tag is not specified, Docker uses the default value of latest, that's all.

Although many repository on Docker Hub use latest as an alias for the latest stable version, this is a convention, not a mandatory one.

So it's best to avoid using latest when using mirrors and explicitly specify a tag, such as httpd:2.3,ubuntu:xenial.

Best practices for using tag

Drawing lessons from the naming method of the software version allows users to make good use of the image.

An efficient version naming scheme allows users to know which image is currently being used while maintaining sufficient flexibility.

Each repository can have multiple tag, and multiple tag may correspond to the same mirror. The following is an example to introduce the tag scheme commonly used in the Docker community.

Suppose we now release a mirror myimage with version v1.9.1. Then we can put four tag:1.9.1, 1.9s, 1s and latest on the image.

We can easily tag the image with the docker tag command.

Docker tag myimage-v1.9.1 myimage:1

Docker tag myimage-v1.9.1 myimage:1.9

Docker tag myimage-v1.9.1 myimage:1.9.1

Docker tag myimage-v1.9.1 myimage:latest

After a while, we released v1.9.2. At this point, you can type 1.9.2 tag and move 1.9,1 and latest from v1.9.1 to v1.9.2.

The command is:

Docker tag myimage-v1.9.2 myimage:1

Docker tag myimage-v1.9.2 myimage:1.9

Docker tag myimage-v1.9.2 myimage:1.9.2

Docker tag myimage-v1.9.2 myimage:latest

After that, v2.0.0 was released. At this point, you can type the tag of 2.0.0,2.0 and 2, and move the latest to v2.0.0.

The command is:

Docker tag myimage-v2.0.0 myimage:2

Docker tag myimage-v2.0.0 myimage:2.0

Docker tag myimage-v2.0.0 myimage:2.0.0

Docker tag myimage-v2.0.0 myimage:latest

This tag scheme makes the version of the image very intuitive, and users are very flexible in their choices:

Myimage:1 always points to the latest mirror in the branch 1.

Myimage:1.9 always points to the latest mirror in 1.9.x.

Myimage:latest always points to the latest image in all versions.

If you want to use a specific version, you can choose myimage:1.9.1, myimage:1.9.2, or myimage:2.0.0.

Many repository on Docker Hub use this solution, so you must be familiar with it.

The above is how to practice the naming of Docker images. Have you learned any knowledge or skills? If you want to learn more skills or enrich your knowledge reserve, you are welcome to follow the industry information channel.

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