CoursesFree Quizzes
DockerImage Creation, Management, and Registry

Add & Url — DCA Practice Question

A representative Docker Certified Associate (DCA) exam question on Add & Url. Work through it below, then read why each option is right or wrong.

This question is part of the free Docker Certified Associate practice test.

Short answer

The correct answer is C. The file is saved as /usr/local/pkg.tar, named from the URL path, and it is not extracted.

The correct answer is C. The file is saved as /usr/local/pkg.tar, named from the URL path, and it is not extracted. A is wrong because remote tar archives are not extracted by default. B is wrong because URL sources are supported, and the trailing slash makes ADD infer the filename. D is wrong because the trailing slash makes ADD infer the filename from the URL path, so the file does get a name.

The Question

A Dockerfile uses ADD https://example.com/tools/pkg.tar /usr/local/ with a trailing slash on the destination. The remote file is a tar archive. What is the result?

AThe archive is downloaded and unpacked into /usr/local/, because ADD extracts every tar archive it fetches
BThe build fails, because ADD cannot download from a URL when the destination ends with a trailing slash
CThe file is saved as /usr/local/pkg.tar, named from the URL path, and it is not extractedCorrect
DThe file is saved as /usr/local/ with no name, and the build step then fails on the missing filename

Why C is correct

The correct answer is C. The file is saved as /usr/local/pkg.tar, named from the URL path, and it is not extracted. A is wrong because remote tar archives are not extracted by default. B is wrong because URL sources are supported, and the trailing slash makes ADD infer the filename. D is wrong because the trailing slash makes ADD infer the filename from the URL path, so the file does get a name.

Why the other options are wrong

Option A: The archive is downloaded and unpacked into /usr/local/, because ADD extracts every tar archive it fetches

Option A does not satisfy the requirement in the scenario. Review the explanation above: the correct choice (C) is the only one that fully meets every constraint stated in the question.

Option B: The build fails, because ADD cannot download from a URL when the destination ends with a trailing slash

Option B does not satisfy the requirement in the scenario. Review the explanation above: the correct choice (C) is the only one that fully meets every constraint stated in the question.

Option D: The file is saved as /usr/local/ with no name, and the build step then fails on the missing filename

Option D does not satisfy the requirement in the scenario. Review the explanation above: the correct choice (C) is the only one that fully meets every constraint stated in the question.

Key idea: Add & Url

The correct answer is C. The file is saved as /usr/local/pkg.tar, named from the URL path, and it is not extracted. A is wrong because remote tar archives are not extracted by default. B is wrong because URL sources are supported, and the trailing slash makes ADD infer the filename. D is wrong because the trailing slash makes ADD infer the filename from the URL path, so the file does get a name. On the DCA exam, questions in the "Image Creation, Management, and Registry" domain test whether you can map a scenario's constraints to the right choice. Read the requirement carefully, eliminate options that violate any single constraint, and pick the one that satisfies all of them with the least operational overhead.

Ready to see how you'd score?

Take the free practice quiz and find out which Docker Certified Associate domains you need to focus on. No signup required.

Take the free quizSee all 327+ practice questions

Practice 5 similar questions

Same cert, same or adjacent domain. Use these after reviewing the explanation.

1Swarm Init & Listen Addr — DCA Practice QuestionOrchestration2Add & Copy — DCA Practice QuestionImage Creation, Management, and Registry3Apt & Docker CE — DCA Practice QuestionInstallation and Configuration4Default Networks & Docker Network ls — DCA Practice QuestionNetworking5Capabilities & Default Security — DCA Practice QuestionSecurity

Related Docker Certified Associate Practice Questions

Swarm Init & Listen Addr — DCA Practice Question→Add & Copy — DCA Practice Question→Apt & Docker CE — DCA Practice Question→

Official sources used

Verify program and exam details at the source before scheduling.

docs.docker.comReference: Dockerfile