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Marco Bytes
Marco Bytes

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How Windows Line Endings Broke My Docker Gradle Build (And How to Fix It)

#docker #devops #springboot #build

Working with Java Spring Boot and Docker, I kept hitting this frustrating error during build:

/bin/sh: ./gradlew: not found
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No matter what I tried, Docker just couldn’t run the Gradle wrapper inside the container. Turns out the culprit was something subtle — Windows CRLF line endings on gradlew.

What’s going on?

  • When you build a Docker image with a Java project using Gradle, the gradlew file must be copied into the container and be executable.
  • But if you’re on Windows, gradlew often has CRLF (Carriage Return + Line Feed) endings instead of Unix’s LF endings.
  • Linux-based containers can’t execute scripts with Windows line endings properly, so it throws a “not found” error.
  • This problem is especially sneaky because your file looks fine on Windows and even inside Docker it shows up — but it silently fails when run.

How to confirm the issue?

  • Check line endings in your editor (VSCode, Notepad++ show line endings).
  • Run file gradlew on Linux — if it shows CRLF line endings, that’s the issue.
  • Add RUN ls -la after COPY in Dockerfile to confirm gradlew is copied.
  • Try running chmod +x ./gradlew — no errors but still ./gradlew: not found.

How to fix it?

Option 1: Fix on your host machine (best)

  • Use tools like dos2unix gradlew locally before building.
  • Configure your Git to checkout with LF line endings: 
  git config --global core.autocrlf input
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  • Set your editor to save files with LF endings.

Option 2: Fix inside Dockerfile (if host fix is impossible) 

RUN apk add --no-cache dos2unix \
 && dos2unix ./gradlew \
 && chmod +x ./gradlew
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Final Dockerfile snippet example 

COPY . .

RUN apk add --no-cache dos2unix \
 && dos2unix ./gradlew \
 && chmod +x ./gradlew

RUN ./gradlew bootJar --no-daemon -x test
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Conclusion

This tiny line endings mismatch wasted hours of debugging for me, but now you know the trick to avoid it.

Make sure to:

  • Check your line endings,
  • Convert them properly,
  • And always test inside your container early.

This simple fix will save you headaches and speed up your Docker + Gradle builds!

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