Docker Info & Backing Filesystem — DCA Practice Question
A representative Docker Certified Associate (DCA) exam question on Docker Info & Backing Filesystem. 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 B. The filesystem on which the directory /var/lib/docker/ is located, which the storage driver builds on.
B is correct: the select-a-storage-driver page defines the backing filesystem as the filesystem where /var/lib/docker/ is located, and docker info reports it next to the storage driver. A is wrong because a registry has no role in this line; it describes the local host. C is wrong because the container root filesystem is built by the storage driver (overlay2) from image layers, not by the backing filesystem line. D is wrong because volumes and bind mounts are separate from the driver's backing filesystem.
The Question
An administrator runs docker info on a Linux host and sees the lines "Storage Driver: overlay2" and "Backing Filesystem: xfs". What does the Backing Filesystem line report?
Why B is correct
B is correct: the select-a-storage-driver page defines the backing filesystem as the filesystem where /var/lib/docker/ is located, and docker info reports it next to the storage driver. A is wrong because a registry has no role in this line; it describes the local host. C is wrong because the container root filesystem is built by the storage driver (overlay2) from image layers, not by the backing filesystem line. D is wrong because volumes and bind mounts are separate from the driver's backing filesystem.
Why the other options are wrong
Option A does not satisfy the requirement in the scenario. Review the explanation above: the correct choice (B) is the only one that fully meets every constraint stated in the question.
Option C does not satisfy the requirement in the scenario. Review the explanation above: the correct choice (B) is the only one that fully meets every constraint stated in the question.
Option D does not satisfy the requirement in the scenario. Review the explanation above: the correct choice (B) is the only one that fully meets every constraint stated in the question.
Key idea: Docker Info & Backing Filesystem
B is correct: the select-a-storage-driver page defines the backing filesystem as the filesystem where /var/lib/docker/ is located, and docker info reports it next to the storage driver. A is wrong because a registry has no role in this line; it describes the local host. C is wrong because the container root filesystem is built by the storage driver (overlay2) from image layers, not by the backing filesystem line. D is wrong because volumes and bind mounts are separate from the driver's backing filesystem. On the DCA exam, questions in the "Storage and Volumes" 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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