Container filesystem is ephemeral in Docker - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the command to start a container that prints a message.

Docker

docker run --rm alpine echo [1]

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

AHello, World!

B"Hello, World!"

C'Hello, World!'

DHello World

Attempts:

3 left

💡 Hint

Common Mistakes

Using quotes that cause the shell to treat the message as a single argument with quotes included.

Forgetting to include the message after echo.

The command docker run --rm alpine echo Hello, World! runs a container that prints the message. Quotes are not needed here.

2fill in blank

medium

Complete the command to create a file inside a container.

Docker

docker run --rm alpine sh -c "echo 'data' > [1]"

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

A/data/file.txt

B/tmp/file.txt

C/var/file.txt

D/file.txt

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing a directory that might not exist or be writable inside the container.

Using root directory which is not recommended for temporary files.

The /tmp directory is commonly used for temporary files inside containers. This file will be created there.

3fill in blank

hard

Fix the error in the command to keep a file after the container stops.

Docker

docker run --rm -v [1]:/data alpine sh -c "echo 'save me' > /data/file.txt"

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

A/var/lib/docker

B/data

C/tmp

D/host/path

Attempts:

3 left

💡 Hint

Common Mistakes

Using a container path on the left side of the volume mount.

Using a system folder that is not intended for mounting.

Mounting a host directory (like /host/path) to /data inside the container saves files outside the ephemeral container filesystem.

4fill in blank

hard

Fill both blanks to create a volume and mount it to persist data.

Docker

docker volume [1] mydata && docker run -v mydata:[2] alpine sh -c "echo 'persist' > /data/file.txt"

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

Acreate

Bdata

C/data

Dremove

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'remove' instead of 'create' for the volume command.

Mounting the volume to a wrong or non-existent container path.

First, create a volume with docker volume create mydata. Then mount it inside the container at /data to persist files.

5fill in blank

hard

Fill all three blanks to explain ephemeral filesystem behavior.

Docker

When a container stops, all files in [1] are lost unless [2] or [3] are used.

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

Athe container's writable layer

Ba volume

Ca bind mount

Dthe image

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing the image with the writable layer.

Not knowing the difference between volumes and bind mounts.

The container's writable layer is ephemeral. To keep data, use volumes or bind mounts which store data outside the container.