Image tags and versioning in Docker - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a Docker image tag?

A Docker image tag is a label that identifies a specific version of a Docker image. It helps you choose which version of the image to use when running containers.

beginner

Why should you use version tags instead of the 'latest' tag?

Using version tags ensures you run a specific, tested image version. The 'latest' tag can change over time, which might cause unexpected behavior or bugs.

beginner

How do you specify a tag when pulling a Docker image?

You add a colon and the tag name after the image name. For example: docker pull ubuntu:22.04 pulls the Ubuntu image tagged '22.04'.

beginner

What happens if you don't specify a tag when pulling a Docker image?

Docker uses the 'latest' tag by default, which means it pulls the image tagged as 'latest'. This might not always be the version you want.

intermediate

How can you tag a local Docker image with a new version?

Use the command docker tag SOURCE_IMAGE[:TAG] TARGET_IMAGE[:TAG]. For example, docker tag myapp:1.0 myapp:1.1 creates a new tag '1.1' for the same image.

What does the Docker tag 'latest' mean?

A It is a tag you must always specify manually

B It always points to the oldest image version

C It is a special tag that deletes images

D It is the default tag if none is specified

If you don't specify a tag, Docker uses 'latest' by default.

How do you pull a specific version of an image named 'nginx' tagged '1.23'?

A docker pull nginx:1.23

B docker pull nginx-1.23

C docker pull nginx/latest

D docker pull nginx

Use a colon and the tag name to pull a specific version.

Why is it risky to always use the 'latest' tag in production?

A Because 'latest' images are always unstable

B Because 'latest' might change and cause unexpected bugs

C Because 'latest' deletes old images automatically

D Because 'latest' is not supported by Docker

'Latest' can point to different image versions over time, which may break your app.

How do you add a new tag '2.0' to an existing local image 'myapp:1.0'?

A docker build myapp:2.0

B docker pull myapp:2.0

C docker tag myapp:1.0 myapp:2.0

D docker push myapp:2.0

The 'docker tag' command creates a new tag for an existing image.

What is the correct format to specify an image with a tag?

A image_name:tag

B image_name/tag

C image_name#tag

D image_name@tag

Docker uses a colon ':' to separate the image name and tag.

Explain why using specific version tags for Docker images is important in software deployment.

Think about what happens if your app suddenly uses a different image version without warning.

Describe how to tag a Docker image locally and why you might want to do this.

Tagging is like giving a nickname to a photo so you can find it easily later.