ARG and ENV instructions in Docker - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the Dockerfile line to declare a build-time variable named VERSION.

Docker

ARG [1]

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AVERSION

BENV

CRUN

DCOPY

Attempts:

3 left

💡 Hint

Common Mistakes

Using ENV instead of ARG for build-time variables

Using RUN or COPY which are unrelated here

The ARG instruction declares a build-time variable. Here, VERSION is the variable name.

2fill in blank

medium

Complete the Dockerfile line to set an environment variable named PATH inside the container.

Docker

ENV [1]=/usr/local/bin

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AHOME

BPATH

CVERSION

DUSER

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing ARG and ENV variables

Using unrelated variable names like HOME or USER

The ENV instruction sets environment variables inside the container. Here, PATH is set to /usr/local/bin.

3fill in blank

hard

Fix the error in this Dockerfile line that tries to use a build argument inside ENV.

Docker

ENV APP_VERSION=[1]

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A$APP_VERSION

BAPP_VERSION

C${APP_VERSION}

DARG_APP_VERSION

Attempts:

3 left

💡 Hint

Common Mistakes

Using $APP_VERSION without braces

Using the literal variable name without expansion

To use a build argument inside an ENV instruction, you reference it with ${APP_VERSION}. This syntax expands the argument value.

4fill in blank

hard

Fill both blanks to declare a build argument and set it as an environment variable with a default value.

Docker

ARG [1]=1.0
ENV [2]=$[1]

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AAPP_VERSION

BVERSION

Attempts:

3 left

💡 Hint

Common Mistakes

Using different names for ARG and ENV

Forgetting the default value in ARG

The build argument is declared as VERSION with a default value. Then ENV sets the environment variable VERSION using the argument's value.

5fill in blank

hard

Fill all three blanks to create a Dockerfile snippet that declares a build argument, sets an environment variable, and uses it in a RUN command.

Docker

ARG [1]=latest
ENV [2]=$[1]
RUN echo "Version is [3]"

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AAPP_TAG

C$APP_TAG

Attempts:

3 left

💡 Hint

Common Mistakes

Using different names for ARG and ENV

Not using $ to reference variables in RUN

The build argument APP_TAG is declared with a default. The environment variable APP_TAG is set from it. The RUN command uses $APP_TAG to print the version.