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Docker Intermediate: Images and Compose That Survive Real Projects
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Docker Intermediate: Images and Compose That Survive Real Projects

Check Yourself: Images Across Machines

Five scenario questions on tags, latest, push errors, digests and platforms. If you miss more than one, reread the lessons in this section.

5 min DockerSecurityDeployment and ContainersPackaging and Dependencies Intermediate
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1. You tagged an image app:1.0.0, app:1.0 and app:latest. How many images are on your disk?
Two, because latest is a copy of the newest tag. Three, one for each tag. None, until you push them to a registry. One. The tags are three names for the same image.
2. Your deployment uses image app:latest. Last week it worked and today it runs a different version. What is the most likely reason?
The version number inside the app changed on its own. Docker updates latest by itself every night. latest is only a name, and someone tagged a different image as latest in the meantime. Deploy an exact version tag instead. latest always means the oldest image.
3. You run docker push app:1.0.0 and get push access denied, insufficient_scope. You are not logged in anywhere. What is the most likely cause?
The image is too big to push. The name has no registry address, so Docker tried Docker Hub's library namespace, which you do not own. Tag the image with the right registry and namespace first. Your Dockerfile is invalid. You must build the image again before pushing.
4. Why is pulling by digest, name@sha256:..., safer than pulling by tag for a release you tested?
A digest makes the download faster. Digests are only used for private registries. A tag can be moved to a different image later, while a digest always identifies exactly the same image. A digest is shorter to type.
5. You build an image on an ordinary PC and pull it on a Raspberry Pi with an ARM processor. The container does not start and the error mentions the platform. What is the cause?
Docker on a Raspberry Pi cannot pull from registries. The registry blocks small computers. The image was built for amd64 only, and the Pi needs an arm64 image, or a multi-platform image. The tag is missing the word arm.

About

Five scenario questions on tags, latest, push errors, digests and platforms. If you miss more than one, reread the lessons in this section.

Duration
5 min
Last update
08/07/2026
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