Pushing and pulling images in GCP - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does 'pushing an image' mean in cloud container registries?

Pushing an image means sending your local container image to a cloud container registry so it can be stored and shared.

beginner

What is the purpose of 'pulling an image' from a container registry?

Pulling an image means downloading a container image from a cloud registry to your local machine or server to run it.

beginner

Which GCP service is commonly used to store container images?

Google Container Registry (GCR) or Artifact Registry are used to store container images in GCP.

intermediate

What command is used to push a Docker image to Google Container Registry?

The command is: docker push gcr.io/[PROJECT-ID]/[IMAGE]:[TAG] where you replace placeholders with your project and image details.

intermediate

Why do you need to authenticate before pushing or pulling images in GCP?

Authentication ensures you have permission to access the container registry and protects your images from unauthorized use.

What is the first step before pushing an image to Google Container Registry?

A Authenticate with GCP using gcloud

B Run the image locally

C Delete old images

D Create a Kubernetes cluster

You must authenticate with GCP using the gcloud tool to have permission to push images.

Which command pulls an image from Google Container Registry?

A kubectl pull image

B docker push gcr.io/project/image:tag

C gcloud pull image

D docker pull gcr.io/project/image:tag

The 'docker pull' command downloads an image from the registry.

Where are container images stored in GCP?

A Google Cloud Storage buckets

B Google Compute Engine

C Google Container Registry

D Google BigQuery

Google Container Registry is designed to store container images.

What does the tag in an image name specify?

A The image size

B The image version or variant

C The registry location

D The container runtime

Tags identify different versions or variants of the same image.

Why is it important to use tags when pushing images?

A To avoid overwriting images unintentionally

B To speed up the push process

C To encrypt the image

D To reduce image size

Tags help manage versions and prevent overwriting images accidentally.

Explain the process of pushing a container image to Google Container Registry.

Think about the steps from local image to cloud storage.

Describe why authentication is necessary when pulling or pushing images in GCP.

Consider security and access control.

Practice

1. What does the docker push command do in Google Cloud Platform?

easy

A. Downloads a container image from Google Container Registry

B. Uploads your container image to Google Container Registry

C. Deletes a container image from your local machine

D. Builds a new container image from a Dockerfile

Solution

1. Step 1: Understand the purpose of docker push

   The docker push command uploads your local container image to a remote registry like Google Container Registry.

2. Step 2: Differentiate from other commands

   docker pull downloads images, docker build creates images, and deleting is a separate action.

3. Final Answer:

   Uploads your container image to Google Container Registry -> Option B

4. Quick Check:

   Push = Upload image to registry [OK]

Hint: Push means upload image to cloud registry [OK]

Common Mistakes:

• Confusing push with pull
• Thinking push builds the image
• Assuming push deletes images

2. Which of the following is the correct syntax to tag a local Docker image named myapp with the Google Container Registry path gcr.io/my-project/myapp:v1?

easy

A. docker tag myapp gcr.io/my-project/myapp:v1

B. docker push myapp gcr.io/my-project/myapp:v1

C. docker pull myapp gcr.io/my-project/myapp:v1

D. docker build myapp gcr.io/my-project/myapp:v1

Solution

1. Step 1: Identify the tagging command

   The docker tag command assigns a new name (including registry path) to an existing local image.

2. Step 2: Confirm correct syntax

   The syntax is docker tag SOURCE_IMAGE TARGET_IMAGE, so docker tag myapp gcr.io/my-project/myapp:v1 is correct.

3. Final Answer:

   docker tag myapp gcr.io/my-project/myapp:v1 -> Option A

4. Quick Check:

   Tag syntax = docker tag SOURCE TARGET [OK]

Hint: Tag uses 'docker tag source target' syntax [OK]

Common Mistakes:

• Using push or pull instead of tag
• Reversing source and target images
• Confusing build with tag

3. Given the commands below, what will be the result of running docker images?

docker tag myapp gcr.io/my-project/myapp:v2
docker push gcr.io/my-project/myapp:v2

medium

A. The local image list will only show myapp without the tag

B. The local image list will be empty

C. The local image list will include gcr.io/my-project/myapp:v2

D. The local image list will show myapp:v2 but not the full registry path

Solution

1. Step 1: Understand tagging effect on local images

   Tagging creates a new name for the same local image, so gcr.io/my-project/myapp:v2 appears locally.

2. Step 2: Recognize push does not remove local images

   Pushing uploads the image but does not delete local copies, so the tagged image remains listed.

3. Final Answer:

   The local image list will include gcr.io/my-project/myapp:v2 -> Option C

4. Quick Check:

   Tag adds local name; push uploads but keeps local image [OK]

Hint: Tag adds local name; push uploads but keeps local image [OK]

Common Mistakes:

• Thinking push deletes local images
• Assuming tag does not create new local name
• Confusing image names without registry path

4. You tried to push an image with the command docker push myapp:v1 but got an error saying the repository was not found. What is the most likely cause?

medium

A. You forgot to tag the image with the full registry path before pushing

B. You need to run docker pull before pushing

C. The image name myapp:v1 is invalid syntax

D. You must delete the local image before pushing

Solution

1. Step 1: Understand push requires full registry path

   To push to Google Container Registry, the image must be tagged with the full path like gcr.io/project-id/image:tag.

2. Step 2: Identify missing tag as cause of error

   Using only myapp:v1 lacks registry info, so the push command cannot find the remote repository.

3. Final Answer:

   You forgot to tag the image with the full registry path before pushing -> Option A

4. Quick Check:

   Push needs full registry tag [OK]

Hint: Push needs full registry path tag [OK]

Common Mistakes:

• Trying to pull before push
• Assuming image name syntax is wrong
• Deleting local image before push

5. You want to update your app image in Google Container Registry with a new version. Which sequence of commands correctly tags, pushes, and then pulls the updated image for deployment?

hard

A. docker build myapp:v2 && docker pull gcr.io/my-project/myapp:v2 && docker push gcr.io/my-project/myapp:v2

B. docker pull gcr.io/my-project/myapp:v2 && docker tag myapp:v2 && docker push myapp:v2

C. docker push myapp:v2 && docker tag myapp gcr.io/my-project/myapp:v2 && docker pull myapp:v2

D. docker tag myapp gcr.io/my-project/myapp:v2 && docker push gcr.io/my-project/myapp:v2 && docker pull gcr.io/my-project/myapp:v2

Solution

1. Step 1: Tag the local image with the full registry path

   Use docker tag myapp gcr.io/my-project/myapp:v2 to prepare the image for pushing.

2. Step 2: Push the tagged image to Google Container Registry

   Run docker push gcr.io/my-project/myapp:v2 to upload the image.

3. Step 3: Pull the updated image to confirm availability for deployment

   Use docker pull gcr.io/my-project/myapp:v2 to download the image where needed.

4. Final Answer:

   docker tag myapp gcr.io/my-project/myapp:v2 && docker push gcr.io/my-project/myapp:v2 && docker pull gcr.io/my-project/myapp:v2 -> Option D

5. Quick Check:

   Tag, push, then pull sequence [OK]

Hint: Tag with full path, push, then pull updated image [OK]

Common Mistakes:

• Pushing before tagging with full path
• Pulling before pushing updated image
• Incorrect command order