Bind mounts expose a host path inside a container. They suit development but couple behavior to host files, ownership and path layout.
Before you start
You should understand the difference between an image, a running container and the host. Record where a file, process or network endpoint actually lives before diagnosing a problem. Commands illustrate local experiments; adapt image names and paths to a disposable development environment.
The practical goal is to reason through this situation: Mount local source into a development container for rapid editing. Read the walkthrough first, then try the interview exercise before opening its answer. The important part is explaining the decision and its consequences, rather than remembering a definition alone.
Step-by-step walkthrough
Step 1: Identify host coupling
A bind mount exposes a particular host path and its permissions.
Step 2: Inspect destination masking
Mounted content hides image files already at the destination.
Step 3: Compare host and image
Check both independently before blaming the build.
Worked scenario
Mount local source into a development container for rapid editing.
An image contains /app/build, but mounting an empty host /app directory hides it. The missing files were packaged correctly; the runtime mount changed visibility. Development mounts also inherit host ownership differences, so a configuration working on one machine may fail elsewhere.
Common mistake
A mount can hide files already present at the container path.
Verify the behavior
Run once without the mount, inspect host contents, then verify the intended mounted path and permissions.
Interview exercise
Diagnose missing application files.
Answer and reasoning
Inspect mount destinations and host contents before assuming the built image omitted the files.
Continue learning
Compare the scenario with the Docker interview questions and test your understanding with the Docker MCQs. For terminology and implementation details, consult the reference material.