Named volumes for data sharing in Docker - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a named volume called 'data_volume'.

Docker

docker volume create [1]

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

Adata_volume

Bvolume1

Cshared_data

Dmy_volume

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different volume name than the one referenced later.

Forgetting to create the volume before using it.

The command docker volume create data_volume creates a named volume called 'data_volume' for sharing data between containers.

2fill in blank

medium

Complete the code to run a container that mounts the named volume 'data_volume' at '/app/data'.

Docker

docker run -d -v [1]:/app/data alpine sleep 1000

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

Adata_volume

Bmy_volume

C/data_volume

Dvolume_data

Attempts:

3 left

💡 Hint

Common Mistakes

Adding a slash before the volume name, which is incorrect.

Using a volume name that was not created.

The -v data_volume:/app/data option mounts the named volume 'data_volume' inside the container at '/app/data'.

3fill in blank

hard

Fix the error in the command to mount the named volume 'data_volume' to '/data' inside the container.

Docker

docker run -d -v [1]:/data alpine sleep 1000

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

Adata_volume/

B/data_volume

Cdata_volume

Dvolume/data

Attempts:

3 left

💡 Hint

Common Mistakes

Adding slashes before or after the volume name.

Using an incorrect volume name format.

The correct syntax for mounting a named volume is -v data_volume:/data. Adding slashes or extra characters causes errors.

4fill in blank

hard

Fill both blanks to define a service in docker-compose that uses the named volume 'data_volume' mounted at '/data'.

Docker

version: '3.8'\nservices:\n  app:\n    image: alpine\n    volumes:\n      - [1]:[2]\nvolumes:\n  data_volume: {}

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

Adata_volume

B/data

C/app/data

Dmy_volume

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping the volume name and mount path.

Using a different volume name than declared.

In docker-compose, the volume is referenced by its name 'data_volume' and mounted at the container path '/data'.

5fill in blank

hard

Fill all three blanks to create a docker-compose service that mounts 'data_volume' at '/data', runs 'sleep 1000', and declares the volume.

Docker

version: '3.8'\nservices:\n  worker:\n    image: alpine\n    command: [1]\n    volumes:\n      - [2]:[3]\nvolumes:\n  data_volume: {}

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

Asleep 1000

Bdata_volume

C/data

Dsleep

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'sleep' without the duration.

Incorrect volume name or mount path.

Forgetting to declare the volume under 'volumes'.

The service runs the command sleep 1000, mounts the named volume 'data_volume' at '/data', and declares the volume under volumes.

Practice

1. What is the main purpose of using named volumes in Docker?

easy

A. To isolate network traffic between containers

B. To speed up container startup time

C. To share and persist data between containers safely

D. To limit CPU usage of containers

Solution

1. Step 1: Understand what named volumes do

   Named volumes store data outside the container's writable layer, allowing data to persist beyond container life.

2. Step 2: Identify the main benefit

   This persistence and sharing of data between containers is the key purpose of named volumes.

3. Final Answer:

   To share and persist data between containers safely -> Option C

4. Quick Check:

   Named volumes = data sharing and persistence [OK]

Hint: Named volumes keep data safe and share it [OK]

Common Mistakes:

• Confusing volumes with network settings
• Thinking volumes improve CPU or speed
• Assuming volumes delete data with containers

2. Which of the following is the correct command to create a named volume called mydata?

easy

A. docker volume create mydata

B. docker create volume mydata

C. docker volume new mydata

D. docker volume make mydata

Solution

1. Step 1: Recall Docker volume creation syntax

   The correct command to create a volume is docker volume create [name].

2. Step 2: Match the command with options

   Only docker volume create mydata uses the correct syntax: docker volume create mydata.

3. Final Answer:

   docker volume create mydata -> Option A

4. Quick Check:

   Volume create command = docker volume create [OK]

Hint: Use 'docker volume create' to make named volumes [OK]

Common Mistakes:

• Swapping order of words in the command
• Using 'new' or 'make' instead of 'create'
• Omitting the 'volume' keyword

3. Given the command:

docker run -d --name app1 -v myvol:/app/data busybox sleep 1000

What happens to the data inside /app/data if the container app1 is removed?

medium

A. Data inside /app/data is saved in the named volume 'myvol'

B. Data inside /app/data is lost unless backed up manually

C. Data inside /app/data is copied to the host's /var/lib/docker folder automatically

D. Data inside /app/data is deleted with the container

Solution

1. Step 1: Understand volume mounting in the command

   The -v myvol:/app/data option mounts the named volume 'myvol' to the container path '/app/data'.

2. Step 2: Know volume persistence behavior

   Named volumes keep data even if the container is removed, so data inside '/app/data' is saved in 'myvol'.

3. Final Answer:

   Data inside /app/data is saved in the named volume 'myvol' -> Option A

4. Quick Check:

   Named volume keeps data after container removal [OK]

Hint: Named volumes keep data safe after container removal [OK]

Common Mistakes:

• Thinking data deletes with container
• Confusing named volumes with anonymous volumes
• Assuming data copies to host automatically

4. You run this command to share data between two containers:

docker run -d --name c1 -v sharedvol:/data busybox sleep 1000
docker run -d --name c2 -v sharedvol:/data busybox sleep 1000

But container c2 cannot see files created by c1 inside /data. What is the likely problem?

medium

A. The volume mount syntax is incorrect

B. Containers must be on the same network to share volumes

C. The volume 'sharedvol' was not created before running containers

D. Files created by c1 are not saved because the container is stopped

Solution

1. Step 1: Check volume creation requirement

   Named volumes must exist or be created automatically. If 'sharedvol' was never created, Docker creates an empty volume.

2. Step 2: Understand volume persistence and sharing

   If 'sharedvol' was not created or data was not saved properly, c2 won't see c1's files. Network does not affect volume sharing.

3. Final Answer:

   Files created by c1 are not saved because the container is stopped -> Option D

4. Quick Check:

   Stopped container does not save files to volume [OK]

Hint: Files must be saved and container running to share data [OK]

Common Mistakes:

• Thinking network affects volume sharing
• Assuming mount syntax is wrong
• Believing stopped containers save files automatically

5. You want to share a folder /var/log/app on your host with multiple containers using a named volume. Which sequence of commands correctly creates and uses the named volume to achieve this?

hard

A. docker volume create app_logs

docker run -d -v /var/log/app:/app/log busybox sleep 1000

B. docker volume create --opt type=none --opt device=/var/log/app --opt o=bind app_logs

docker run -d -v app_logs:/app/log busybox sleep 1000

C. docker volume create app_logs

docker run -d -v app_logs:/var/log/app busybox sleep 1000

D. docker run -d -v app_logs:/app/log busybox sleep 1000

Solution

1. Step 1: Create a named volume that binds to host folder

   Use docker volume create with options type=none, device=/var/log/app, and o=bind to bind the host folder to the volume.

2. Step 2: Run container mounting the named volume

   Mount the named volume app_logs to the container path /app/log with -v app_logs:/app/log.

3. Final Answer:

   docker volume create --opt type=none --opt device=/var/log/app --opt o=bind app_logs docker run -d -v app_logs:/app/log busybox sleep 1000 -> Option B

4. Quick Check:

   Bind host folder with volume create options [OK]

Hint: Use volume create with bind options for host folder sharing [OK]

Common Mistakes:

• Mounting host folder directly without volume create
• Mounting volume to wrong container path
• Skipping volume creation step