[Solved] Given this Dockerfile snippet:FROM python:3.12-slim RUN pip install flask COPY app.py /app/ RUN python /app/app.pyWhich layer will be rebuilt if only app.py changes during CI build? | Docker

Docker - in CI/CD

Given this Dockerfile snippet:

FROM python:3.12-slim
RUN pip install flask
COPY app.py /app/
RUN python /app/app.py

Which layer will be rebuilt if only app.py changes during CI build?

AThe FROM python:3.12-slim base image layer

BThe RUN pip install flask layer

CAll layers will be rebuilt

DThe last RUN layer running the app.py script

Step-by-Step Solution

Solution:

Step 1: Understand layer caching and COPY instruction
Changing app.py affects the COPY instruction and any layers after it.
Step 2: Identify which RUN layer depends on app.py
The last RUN runs app.py, so it must be rebuilt; earlier layers remain cached.
Final Answer:
The last RUN layer running the app.py script -> Option D
Quick Check:
Changed file affects subsequent layers only [OK]

Quick Trick: Only layers after changed files rebuild in Docker cache [OK]

Common Mistakes:

Master "in CI/CD" in Docker

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