200-901 Application Deployment and Security Practice Question
A developer creates a Dockerfile for a Python web application. Which instruction should be used to define the working directory inside the container for subsequent commands?
⚠ Common exam trap
Cisco often tests the distinction between WORKDIR and RUN cd, where candidates mistakenly think RUN cd sets a persistent working directory, but in Docker each RUN command runs in a new shell with the working directory reset unless WORKDIR is used.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
WORKDIR
The WORKDIR instruction in a Dockerfile sets the working directory for any RUN, CMD, ENTRYPOINT, COPY, and ADD instructions that follow it in the Dockerfile. For a Python web application, using WORKDIR /app ensures that subsequent commands like COPY and RUN operate inside the /app directory, keeping the container filesystem organized and avoiding path errors.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
ENV
Why it's wrong here
ENV sets environment variables, not the working directory.
- ✗
RUN
Why it's wrong here
RUN executes commands in the current working directory, but does not set a new working directory.
- ✗
COPY
Why it's wrong here
COPY copies files from the host to the container, but does not set the working directory.
- ✓
WORKDIR
Why this is correct
WORKDIR sets the working directory for all subsequent Dockerfile instructions.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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