Image tags and versioning in Docker - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the command to pull the latest version of the nginx image.

Docker

docker pull nginx:[1]

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

Alatest

Bstable

Cold

Dnewest

Attempts:

3 left

💡 Hint

Common Mistakes

Using tags like 'old' or 'newest' which do not exist.

Forgetting to specify a tag and expecting a specific version.

The latest tag is used to pull the most recent version of an image by default.

2fill in blank

medium

Complete the command to tag a local image with version 1.2 before pushing.

Docker

docker tag myapp:dev myrepo/myapp:[1]

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

A1.2

Blatest

Cstable

Ddev

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'dev' as a version tag when pushing to a repository.

Using 'latest' when a specific version is required.

Version tags like 1.2 specify the image version explicitly.

3fill in blank

hard

Fix the error in the command to push version 2.0 of the image to the repository.

Docker

docker push myrepo/myapp:[1]

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

Av2.0

B2.0

Cversion2

D2

Attempts:

3 left

💡 Hint

Common Mistakes

Using incomplete or mismatched tags causing push failures.

Adding prefixes not matching the tag format.

Tags should match the exact version format used when tagging the image, usually numeric like 2.0.

4fill in blank

hard

Fill both blanks to build an image named 'webapp' with version 3.5 from the current directory.

Docker

docker build -t [1]:[2] .

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

Awebapp

B3.5

Clatest

Dapp

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'latest' as version when a specific version is requested.

Using wrong image names.

The -t option tags the image with name and version. Here, 'webapp' is the name and '3.5' is the version.

5fill in blank

hard

Fill all three blanks to create a dictionary comprehension that maps image names to their version tags if the version is greater than 1.0.

Docker

versions = {name: [1] for name, [2] in images.items() if [3] > 1.0}

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

Atag

Dversion

Attempts:

3 left

💡 Hint

Common Mistakes

Using inconsistent variable names causing errors.

Using the wrong variable in the condition.

The dictionary comprehension extracts the version tag for each image. The variable tag is used to compare if it's greater than 1.0.

Practice

1. What is the default tag used by Docker if no tag is specified when pulling an image?

easy

A. stable

B. 1.0

C. latest

D. default

Solution

1. Step 1: Understand Docker image tagging

   Docker images can have tags to specify versions or variants.

2. Step 2: Identify the default tag behavior

   If no tag is specified, Docker uses the tag named "latest" by default.

3. Final Answer:

   latest -> Option C

4. Quick Check:

   Default tag = latest [OK]

Hint: No tag means Docker uses 'latest' automatically [OK]

Common Mistakes:

• Assuming 'stable' is default tag
• Thinking '1.0' is default version
• Believing 'default' is a valid tag

2. Which of the following is the correct syntax to pull a Docker image with a specific tag?

easy

A. docker pull ubuntu:20.04

B. docker pull ubuntu-20.04

C. docker pull ubuntu/20.04

D. docker pull ubuntu#20.04

Solution

1. Step 1: Recall Docker image tag syntax

   The correct syntax to specify a tag is image_name:tag.

2. Step 2: Match syntax with options

   Only docker pull ubuntu:20.04 uses a colon to separate image name and tag correctly.

3. Final Answer:

   docker pull ubuntu:20.04 -> Option A

4. Quick Check:

   Use colon ':' to specify tag [OK]

Hint: Use ':' between image name and tag [OK]

Common Mistakes:

• Using dash '-' instead of colon ':'
• Using slash '/' instead of colon
• Using hash '#' instead of colon

3. Given the command docker pull nginx:1.21, what will be the result?

medium

A. Docker throws an error due to invalid tag

B. Docker pulls the latest nginx image ignoring 1.21

C. Docker pulls all nginx images

D. Docker pulls the nginx image tagged 1.21

Solution

1. Step 1: Analyze the pull command with tag

   The command specifies the image name 'nginx' and tag '1.21'.

2. Step 2: Understand Docker pull behavior

   Docker pulls the exact image version matching the tag '1.21'.

3. Final Answer:

   Docker pulls the nginx image tagged 1.21 -> Option D

4. Quick Check:

   Tag specifies exact image version [OK]

Hint: Tag pulls specific image version, not latest [OK]

Common Mistakes:

• Assuming tag is ignored and latest is pulled
• Expecting error for valid tag
• Thinking all images are pulled

4. You run docker pull alpine and get an error that the image is not found. What is the most likely cause?

medium

A. You forgot to specify the tag, and 'latest' tag is missing

B. The image 'alpine' does not exist on Docker Hub

C. Docker requires a tag to pull any image

D. Your internet connection is down

Solution

1. Step 1: Understand default tag behavior

   When no tag is specified, Docker tries to pull the 'latest' tag.

2. Step 2: Identify cause of error

   If the 'latest' tag does not exist for 'alpine', Docker cannot find the image.

3. Final Answer:

   You forgot to specify the tag, and 'latest' tag is missing -> Option A

4. Quick Check:

   Missing 'latest' tag causes pull failure [OK]

Hint: Always specify tag if 'latest' is missing [OK]

Common Mistakes:

• Assuming image does not exist at all
• Thinking tag is always required
• Blaming internet without checking tags

5. You want to deploy a Docker image but ensure you always use version 2.5.3, never the latest. Which command correctly pulls this specific version and avoids accidental updates?

hard

A. docker pull myapp:stable

B. docker pull myapp:2.5.3

C. docker pull myapp:latest

D. docker pull myapp

Solution

1. Step 1: Understand version control with tags

   Using a specific tag like '2.5.3' ensures you get that exact version.

2. Step 2: Compare options for safety

   docker pull myapp:2.5.3 pulls the exact version. Options B and C pull 'latest' which can change. docker pull myapp:stable depends on tag existence.

3. Final Answer:

   docker pull myapp:2.5.3 -> Option B

4. Quick Check:

   Explicit version tag prevents accidental updates [OK]

Hint: Always specify exact version tag to avoid surprises [OK]

Common Mistakes:

• Using 'latest' tag and getting unexpected updates
• Assuming 'stable' tag always exists
• Not specifying any tag and risking version changes