Troubleshooting Minecraft Server.jar Issues on Raspberry Pi: A Beginner's Guide

Setting up a Minecraft server on a Raspberry Pi can be a rewarding project, allowing you to create your own private Minecraft world. However, like any server setup, you might encounter some hiccups along the way. One common issue arises when dealing with the minecraft server.jar file, especially if you’re new to server administration or Linux environments. Let’s break down a typical problem and explore how to resolve it.

Many users, particularly those using PaperMC for optimized performance, might face errors when initially running their server. You might have downloaded Java 17, obtained the server.jar file, and tried executing the command:

java -Xmx2048M -Xms2048M -jar server.jar nogui

Only to be greeted with an error message like “Failed to download original jar” or, after attempting to use a renamed original Minecraft server.jar file, an AccessDeniedException. This error, as seen below, can be perplexing:

Unpacking 1.18.2/server-1.18.2.jar (versions:1.18.2) to versions/1.18.2/server-1.18.2.jar java.nio.file.AccessDeniedException: /home/pi/myssd/papermcservergoede/versions at java.base/sun.nio.fs.UnixException.translateToIOException(UnixException.java:90) at java.base/sun.nio.fs.UnixException.rethrowAsIOException(UnixException.java:106) at java.base/sun.nio.fs.UnixException.rethrowAsIOException(UnixException.java:111) at java.base/sun.nio.fs.UnixFileSystemProvider.createDirectory(UnixFileSystemProvider.java:398) at java.base/java.nio.file.Files.createDirectory(Files.java:700) at java.base/java.nio.file.Files.createAndCheckIsDirectory(Files.java:807) at java.base/java.nio.file.Files.createDirectories(Files.java:793) at net.minecraft.bundler.Main.extractJar(Main.java:105) at net.minecraft.bundler.Main.checkAndExtractJar(Main.java:100) at net.minecraft.bundler.Main.readAndExtractDir(Main.java:92) at net.minecraft.bundler.Main.run(Main.java:38) at net.minecraft.bundler.Main.main(Main.java:25) Failed to extract server libraries, exiting

This AccessDeniedException essentially means that the Java process doesn’t have the necessary permissions to create directories or write files in the location you are trying to set up your Minecraft server. Let’s troubleshoot this step-by-step.

Understanding and Fixing the Access Denied Error

The “AccessDeniedException” when launching minecraft server.jar usually points to a permissions problem within your Raspberry Pi’s file system. Here’s how to diagnose and fix it:

Check File Permissions: The most common cause is incorrect permissions on the directory where you are trying to run the minecraft server.jar. Linux systems have a permission system that controls who can read, write, and execute files and directories.
- Command to Check Permissions: Open your Raspberry Pi terminal and navigate to the directory containing your server.jar file. Use the command ls -l to list files and their permissions.
```
ls -l
```
- Understanding the Output: Look at the permissions for your server directory (e.g., papermcservergoede in the original example). You need to ensure that the user running the Java command (likely the pi user) has write permissions in this directory. Permissions are displayed like drwxr-xr-x. The first character ‘d’ indicates a directory. The next three rwx are permissions for the owner, the next three for the group, and the last three for others. r means read, w means write, and x means execute.
- Fixing Permissions: If you find that the permissions are too restrictive, you can use the chmod command to change them. To give the owner (likely user pi) full read, write, and execute permissions, use:
```
chmod u+rwx .
```
  Run this command from within your server directory. This command adds (+) read, write, and execute permissions (rwx) for the user (u) to the current directory (.).
Verify Java Installation: While less likely to cause an AccessDeniedException directly, an improperly installed or incorrect version of Java can lead to unexpected errors. Ensure you have Java 17 installed correctly and that it is the version being used.
- Check Java Version: Run java -version in your terminal. It should output information confirming Java 17 is installed.
```
java -version
```
Correct Command Syntax: Double-check the command you are using to launch the server. While java -Xmx2048M -Xms2048M -jar server.jar nogui is generally correct, ensure there are no typos. Also, verify that server.jar is indeed the correct filename and is in the directory you are running the command from.
Disk Space: In rare cases, insufficient disk space can manifest as permission-like errors. Ensure your Raspberry Pi’s SD card or SSD has enough free space. Use the df -h command to check disk space usage.
```
df -h
```
Directory Issues: As the original poster noted, special characters in directory names can sometimes cause issues, although this is less common with modern systems. While “papermcservergoede” doesn’t contain special characters, ensure there are no hidden or unusual characters in your directory path. It’s best practice to stick to standard alphanumeric characters for directory and file names.

Alt text: A Raspberry Pi 4 Model B is shown connected to a monitor displaying a Minecraft server interface, keyboard, and mouse, illustrating a typical setup for running a Minecraft server on a Raspberry Pi, emphasizing the accessibility and compact nature of a Raspberry Pi Minecraft server.

Best Practices for Running Minecraft Server.jar on Raspberry Pi

Use PaperMC: PaperMC is a highly optimized fork of Spigot, designed to improve Minecraft server performance significantly. It’s especially beneficial on resource-constrained devices like Raspberry Pi. Always download your server.jar from the official PaperMC website.
Allocate Appropriate RAM: The -Xmx2048M and -Xms2048M flags in the startup command allocate 2GB of RAM to the server. For a Raspberry Pi 4B 4GB, this might be acceptable for a small server. Adjust these values based on the number of players and your Pi’s RAM. Don’t allocate more RAM than your system has available.
Keep Your System Updated: Regularly update your Raspberry Pi OS to ensure you have the latest security patches and software updates, which can contribute to system stability and performance. Use sudo apt update && sudo apt upgrade.

By systematically checking permissions, Java installation, command syntax, and disk space, you should be able to resolve the AccessDeniedException and get your minecraft server.jar running smoothly on your Raspberry Pi, paving the way for your Minecraft adventures. Remember to always refer to official documentation and community forums for further assistance if needed.