Fabric Server on Zulu OpenJDK

A lightweight, high-performance Docker image for running a Fabric Minecraft server. It is built on top of Azul Zulu OpenJDK (Alpine Linux) to ensure minimal footprint and maximum performance.

❓ What is this?

This project provides a production-ready Docker image for hosting a Fabric Minecraft Server. It handles the installation of the specific Fabric Loader and Installer versions defined in the repository, ensuring reproducibility.

🛠 How it works

Unlike other images that download the latest version on every startup, this image uses a Pinned Version Strategy:

1. An automated workflow checks daily for new Fabric updates.
2. If an update is found, it validates it and creates a Pull Request to this repository.
3. Upon merging, a new Docker image is built with those exact versions baked in.
4. Your server downloads this immutable image, ensuring that latest assumes a tested and specific version, preventing random breaks on restart.

💡 Why was this made?

• Performance: Usign Alpine Linux + Zulu OpenJDK provides a very slim and fast Java environment.
• Stability: By pinning versions in the image build process (instead of a startup script), we guarantee that the server environment is identical across restarts until you explicitly decide to update the image.
• Simplicity: No complex startup flags to configure versions; just pull and run.

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🚀 Quick Start

Option 1: Docker Compose (Recommended)

This is the easiest way to manage your server.

1. Create a docker-compose.yml file:

   services:
     minecraft:
       image: ghcr.io/alvarosdev/zulu-fabricmc:latest
       container_name: fabricserver
       restart: unless-stopped
       ports:
         - "25565:25565"
       volumes:
         - ./minecraft_data:/data
       environment:
         - MEMORYSIZE=4G
         - TZ=America/Santiago

2. Start the server:

   docker-compose up -d

Option 2: Docker CLI

If you prefer running a single command:

docker run -d \
  --name fabricserver \
  -p 25565:25565 \
  -v $(pwd)/minecraft_data:/data \
  -e MEMORYSIZE=4G \
  ghcr.io/alvarosdev/zulu-fabricmc:latest

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📦 Managing Mods & Data

All your server data (world, mods, configs) is stored in the mounted volume (e.g., ./minecraft_data).

To install mods:

1. Download the .jar files for your mods (matching the Minecraft version).
2. Place them in the minecraft_data/mods folder.
3. Restart the server.

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🤖 Using the Makefile

This project includes a Makefile to simplify common operations. You can use it if you have make installed (Linux/macOS/WSL).

Command	Description
make up	Starts the server in background (docker-compose up -d).
make stop	Stops the server gracefully (docker-compose stop).
make down	Stops and removes containers and networks (keeps volumes).
make restart	Restarts the container (useful after adding mods).
make logs	Follows the last 50 lines of logs.
make attach	Attaches to the server console. Use Ctrl+P, Ctrl+Q to detach! Ctrl+C will kill the server.
make update	Pulls the latest image and restarts the server (replaces make update-container).
make build	Rebuilds the image locally using the Dockerfile with zero cache.
make clean	WARNING: Stops server and deletes ALL data (including world/mods).

Example:

make logs