Pushing images to registry in Docker - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the command to push a Docker image named myapp to the default registry.

Docker

docker push [1]

Drag options to blanks, or click blank then click option'

Aimage myapp

Bmyapp

Cdocker myapp

Dpush myapp

Attempts:

3 left

💡 Hint

Common Mistakes

Including extra words like 'push' or 'image' after the command.

Using 'docker myapp' which is not a valid command.

The docker push command requires the image name to push it to the registry. Here, myapp is the image name.

2fill in blank

medium

Complete the command to tag a local image myapp with the registry URL registry.example.com/myapp.

Docker

docker tag myapp [1]

Drag options to blanks, or click blank then click option'

Aregistry.example.com/myapp

Bmyapp:latest

Cregistry/myapp

Dexample.com/myapp

Attempts:

3 left

💡 Hint

Common Mistakes

Using only the image name without the registry URL.

Using incomplete or incorrect registry URLs.

To push an image to a remote registry, you must tag it with the full registry URL. Here, registry.example.com/myapp is the correct tag.

3fill in blank

hard

Fix the error in the command to push the image registry.example.com/myapp to the registry.

Docker

docker [1] registry.example.com/myapp

Drag options to blanks, or click blank then click option'

Abuild

Btag

Cpull

Dpush

Attempts:

3 left

💡 Hint

Common Mistakes

Using pull instead of push.

Using tag which only renames images locally.

The docker push command uploads the image to the registry. Using pull or tag here is incorrect.

4fill in blank

hard

Complete the command to push the myapp image to registry.example.com/user/myapp:latest.

Docker

docker push registry.example.com[1]myapp[2]

Drag options to blanks, or click blank then click option'

A/user/

B:latest

C/admin/

D@sha256:abc123

Attempts:

3 left

💡 Hint

Common Mistakes

Omitting the namespace path.

Forgetting to specify the image tag.

The full image reference is registry.example.com/user/myapp:latest. Insert the namespace /user/ and tag :latest.

5fill in blank

hard

Fill all three blanks to build and push the Docker image with the 'latest' tag to the registry.

Docker

docker build -t registry.example.com/myapp[1] . && docker [2] registry.example.com/myapp[3]

Drag options to blanks, or click blank then click option'

A:latest

Bpush

Crun

D:v1.0

Attempts:

3 left

💡 Hint

Common Mistakes

Using run or build instead of push.

Using a different tag like :v1.0 instead of :latest.

Omitting the tag in one of the commands.

Specify :latest as the tag in the build command's -t flag and again in push. Use push to upload to the registry.

Practice

1.

What is the main purpose of the docker push command?

easy

A. Remove a Docker image from local storage

B. Download an image from a remote registry

C. Run a container from an image

D. Upload a local Docker image to a remote registry

Solution

1. Step 1: Understand the command purpose

   The docker push command is used to send a local image to a remote registry so others can access it.

2. Step 2: Compare options with command function

   Downloading images uses docker pull, running containers uses docker run, and removing images uses docker rmi. Only uploading matches docker push.

3. Final Answer:

   Upload a local Docker image to a remote registry -> Option D

4. Quick Check:

   Push means upload image [OK]

Hint: Push means upload your image to share it [OK]

Common Mistakes:

• Confusing push with pull (download)
• Thinking push runs containers
• Assuming push deletes images

2.

Which of the following is the correct syntax to push a Docker image named myapp with tag v1 to Docker Hub?

docker push ________

easy

A. myapp:v1

B. myapp

C. myapp:v1 latest

D. push myapp:v1

Solution

1. Step 1: Recall push command syntax

   The correct syntax is docker push [repository]:[tag]. The tag is required if not using default 'latest'.

2. Step 2: Analyze options

   myapp:v1 uses myapp:v1 which is correct. myapp misses the tag. myapp:v1 latest has extra word 'latest' which is invalid. push myapp:v1 repeats 'push' which is wrong.

3. Final Answer:

   myapp:v1 -> Option A

4. Quick Check:

   Push needs image name and tag [OK]

Hint: Use image name with tag like repo:tag [OK]

Common Mistakes:

• Omitting the tag when required
• Adding extra words after image name
• Repeating the push command inside

3.

Given the commands below, what will be the output of the docker push command?

docker tag myapp:latest myrepo/myapp:v2
docker push myrepo/myapp:v2

medium

A. Image pushed successfully to myrepo/myapp:v2

B. Error: image not found locally

C. Authentication required before push

D. Image pushed but with tag 'latest'

Solution

1. Step 1: Understand tagging and pushing

   The image myapp:latest is tagged as myrepo/myapp:v2, preparing it for push to myrepo registry.

2. Step 2: Predict push output

   Since the image is tagged correctly and assuming user is logged in, the push will succeed with a success message.

3. Final Answer:

   Image pushed successfully to myrepo/myapp:v2 -> Option A

4. Quick Check:

   Tag then push means success [OK]

Hint: Tag image with repo before push [OK]

Common Mistakes:

• Forgetting to tag image before push
• Not logging in to registry
• Assuming default tag is always 'latest'

4.

What is wrong with the following commands if the push fails?

docker push myapp:v1

Assuming myapp:v1 is a local image and the user wants to push to Docker Hub.

medium

A. The push command syntax is incorrect

B. Image is not tagged with the Docker Hub repository name

C. Docker daemon is not running

D. The image tag 'v1' is invalid

Solution

1. Step 1: Check image tagging for remote push

   To push to Docker Hub, the image must be tagged with the repository name like username/myapp:v1.

2. Step 2: Identify the cause of failure

   Since the image is only myapp:v1 without repo prefix, Docker Hub rejects the push.

3. Final Answer:

   Image is not tagged with the Docker Hub repository name -> Option B

4. Quick Check:

   Push needs repo prefix [OK]

Hint: Tag image with repo name before pushing [OK]

Common Mistakes:

• Trying to push without repo prefix
• Assuming push syntax is wrong
• Ignoring Docker daemon status

5.

You want to push a local image webapp:latest to a private registry at registry.example.com. Which sequence of commands is correct?

hard

A. docker login registry.example.comdocker push webapp:latest

B. docker push webapp:latestdocker login registry.example.com

C. docker login registry.example.comdocker tag webapp:latest registry.example.com/webapp:latestdocker push registry.example.com/webapp:latest

D. docker tag webapp:latest registry.example.com/webappdocker push webapp:latest

Solution

1. Step 1: Login to the private registry

   You must log in first to authenticate with registry.example.com.

2. Step 2: Tag the image with the registry URL

   Tag webapp:latest as registry.example.com/webapp:latest so Docker knows where to push.

3. Step 3: Push the tagged image to the registry

   Push the correctly tagged image to upload it to the private registry.

4. Final Answer:

   docker login registry.example.com docker tag webapp:latest registry.example.com/webapp:latest docker push registry.example.com/webapp:latest -> Option C

5. Quick Check:

   Login, tag with registry, then push [OK]

Hint: Login, tag with registry URL, then push [OK]

Common Mistakes:

• Pushing before login
• Not tagging with registry URL
• Pushing wrong image name