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Apt & Docker CE — DCA Practice Question

A representative Docker Certified Associate (DCA) exam question on Apt & Docker CE. 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. docker.io, because the distribution package conflicts with the docker-ce packages from Docker.

The correct answer is C. The official Ubuntu instructions list docker.io, docker-compose, docker-compose-v2, docker-doc, docker-buildx, podman-docker, and any earlier containerd or runc as unofficial packages to remove before installing from Docker's repository. A is wrong because ca-certificates is a prerequisite that the instructions install with apt, not a package to remove. B is wrong because docker-buildx-plugin is one of the packages the instructions install from Docker's repository; only the older docker-buildx package from the distribution conflicts. D is wrong because containerd.io is itself part of the install command; only a previously installed distribution containerd or runc must be removed.

The Question

A Ubuntu server has the distribution package that provides the Docker command installed. An administrator now wants to install Docker Engine from Docker's own apt repository. Which package do the official instructions tell the administrator to remove first?

Aca-certificates, because Docker's repository uses its own certificate authority bundle instead
Bdocker-buildx-plugin, because the repository ships a newer builder that cannot coexist with it
Cdocker.io, because the distribution package conflicts with the docker-ce packages from DockerCorrect
Dcontainerd.io, because Docker's repository installs a different container runtime named runc

Why C is correct

The correct answer is C. The official Ubuntu instructions list docker.io, docker-compose, docker-compose-v2, docker-doc, docker-buildx, podman-docker, and any earlier containerd or runc as unofficial packages to remove before installing from Docker's repository. A is wrong because ca-certificates is a prerequisite that the instructions install with apt, not a package to remove. B is wrong because docker-buildx-plugin is one of the packages the instructions install from Docker's repository; only the older docker-buildx package from the distribution conflicts. D is wrong because containerd.io is itself part of the install command; only a previously installed distribution containerd or runc must be removed.

Why the other options are wrong

Option A: ca-certificates, because Docker's repository uses its own certificate authority bundle instead

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: docker-buildx-plugin, because the repository ships a newer builder that cannot coexist with it

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: containerd.io, because Docker's repository installs a different container runtime named runc

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: Apt & Docker CE

The correct answer is C. The official Ubuntu instructions list docker.io, docker-compose, docker-compose-v2, docker-doc, docker-buildx, podman-docker, and any earlier containerd or runc as unofficial packages to remove before installing from Docker's repository. A is wrong because ca-certificates is a prerequisite that the instructions install with apt, not a package to remove. B is wrong because docker-buildx-plugin is one of the packages the instructions install from Docker's repository; only the older docker-buildx package from the distribution conflicts. D is wrong because containerd.io is itself part of the install command; only a previously installed distribution containerd or runc must be removed. On the DCA exam, questions in the "Installation and Configuration" 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.

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Official sources used

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docs.docker.comInstall: Ubuntu