[Solved] You wrote this Dockerfile line:RUN --mount=type=cache,target=/root/.cache npm installBut the cache is not speeding up builds. What is the likely mistake? | Docker

Docker - Image Optimization

You wrote this Dockerfile line:

RUN --mount=type=cache,target=/root/.cache npm install

But the cache is not speeding up builds. What is the likely mistake?

AThe cache mount target directory is incorrect or not used by npm

BYou forgot to add <code>--cache</code> flag instead of <code>--mount</code>

CCache mounts only work with Python, not npm

DYou must run <code>docker build</code> with <code>--no-cache</code> option

Step-by-Step Solution

Solution:

Step 1: Check cache mount target relevance
Cache mount must target the directory where npm stores cache files, usually /root/.npm, not /root/.cache.
Step 2: Understand npm cache usage
If the target directory is wrong, npm won't use the cache, so builds stay slow.
Final Answer:
The cache mount target directory is incorrect or not used by npm -> Option A
Quick Check:
Correct cache target directory needed = C [OK]

Quick Trick: Match cache target to tool's actual cache folder [OK]

Common Mistakes:

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