engineering:computer_science:docker:dockerfile_good_practices [Carlos Sousa Wiki]

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====== Dockerfile Good Practices ======

**Tags:** #docker #dockerfile #goodpractice #dockerbuild

**Last Reviewed:** 29/08/2024

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**Incremental Build Time:**

  * **Tip #1: Order matters for caching**
      * Organize Dockerfile instructions from least to most frequently changing steps to optimize caching.
  * **Tip #2: Specific COPY commands**
      * Avoid using ''COPY .''  and instead specify only the necessary files to prevent unnecessary cache busts.
  * **Tip #3: Cacheable units for installations**
      * Combine related commands like ''apt-get update''  and package installations in one ''RUN''  instruction to ensure they are treated as a single cacheable unit.

**Image Size:**

  * **Tip #4: Remove unnecessary dependencies**
      * Avoid installing unnecessary packages or debugging tools to reduce the image size.
  * **Tip #5: Remove package manager cache**
      * Clear the package manager cache in the same ''RUN''  instruction that installs packages to prevent it from increasing the image size.

**Maintainability:**

  * **Tip #6: Use official images when possible**
      * Official images are well-maintained and help reduce maintenance effort across multiple projects.
  * **Tip #7: Use more specific tags**
      * Avoid using the ''latest''  tag; instead, use more specific tags to prevent breaking changes.
  * **Tip #8: Look for minimal flavors**
      * Use smaller variants of images (e.g., ''slim''  or ''alpine'') to further reduce the image size while being cautious of compatibility issues.

**Reproducibility:**

  * **Tip #9: Build from source in a consistent environment**
      * Build your application directly within the Docker environment to avoid inconsistencies across different machines.
  * **Tip #10: Fetch dependencies in a separate step**
      * Isolate dependency fetching in its own cacheable step to prevent unnecessary re-downloading when only the source code changes.

**Multi-Stage Builds:**

  * **Tip #11: Use multi-stage builds to remove build dependencies**
      * Use multiple ''FROM''  statements to separate the build environment from the final runtime environment. This technique allows you to include only the necessary runtime dependencies in the final image, resulting in a smaller, more efficient image.