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DL3009: Delete the apt-get lists after installing

Info Efficiency

Why This Matters

After apt-get update && apt-get install, the package lists in /var/lib/apt/lists/ remain in the image layer, adding 20-40 MB of unnecessary data. This bloats your image and slows down container pulls across your cluster. Always remove apt lists in the same RUN instruction to keep the layer lean.

How to Fix

Add rm -rf /var/lib/apt/lists/* in the same RUN instruction

Before (incorrect)

RUN apt-get update && apt-get install -y curl

After (correct)

RUN apt-get update && apt-get install -y curl \
    && rm -rf /var/lib/apt/lists/*

Rule Details

Rule Code
DL3009
Severity
Info
Category
Efficiency

Related Rules

DL3014 Warning

Use the -y switch for apt-get install
DL3003 Warning

Use WORKDIR to switch directories
DL4006 Warning

Set the SHELL option -o pipefail before RUN with a pipe in
DL3042 Warning

Avoid use of cache directory with pip
DL3059 Info

Multiple consecutive RUN instructions