docker-minecraft-server/docs/misc/troubleshooting.md

To troubleshoot the container initialization, such as when server files are pre-downloaded, set the environment variable DEBUG to true. The container logs will include much more output, and it is highly recommended including that output when reporting any issues.

To troubleshoot just the command-line used to start the Minecraft server, set the environment variable DEBUG_EXEC to true.

To troubleshoot any issues with memory allocation reported by the JVM, set the environment variable DEBUG_MEMORY to true.