Linux Java Runtime Environment 🎁

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COPY --chown=appuser:appuser myapp.jar /app/ linux java runtime environment

# Check JAR's required version javap -verbose MyClass.class | grep "major version" # 52 = Java 8, 55 = Java 11, 61 = Java 17, 65 = Java 21 Minimal Dockerfile using Alpine + OpenJDK JRE : : COPY --chown=appuser:appuser myapp

# Run with java explicitly java -jar myapp.jar chmod +x myapp.jar 10.5 "UnsupportedClassVersionError" Cause : JAR compiled with newer Java than your JRE. 55 = Java 11

# Reduce heap size java -Xmx256m -jar app.jar free -h 10.3 "No X11 DISPLAY variable" (headless GUI error) Fix : Run in headless mode:

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COPY --chown=appuser:appuser myapp.jar /app/

# Check JAR's required version javap -verbose MyClass.class | grep "major version" # 52 = Java 8, 55 = Java 11, 61 = Java 17, 65 = Java 21 Minimal Dockerfile using Alpine + OpenJDK JRE :

# Run with java explicitly java -jar myapp.jar chmod +x myapp.jar 10.5 "UnsupportedClassVersionError" Cause : JAR compiled with newer Java than your JRE.

# Reduce heap size java -Xmx256m -jar app.jar free -h 10.3 "No X11 DISPLAY variable" (headless GUI error) Fix : Run in headless mode: