Minecraft Server on Docker ⛏ 🐳

Introduction

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Minecraft is a great game and better with friends. A dedicated server allows you to do that¹.

A Minecraft server does not require a ton of resources to run, but from my experience the more resources you can throw at it the better when you start to introduce mods and more players.

I run our server on my main PC. This allows me to leverage the system resources in my PC 🦾 leaving the Pi Cluster system resources to handle the rest of the stuff in my lab.

Prerequisites

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• Docker
• Docker Compose

Requirements²

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Minimum (1-5 Players)

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• Intel Pentium 4 or AMD Athlon based CPU
• 512 MB RAM
• 2 GB Storage space

Recommended (10-15 Players)

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• Intel Core or AMD K8 based CPU
• 3 GB RAM
• 16 GB Storage Space

Optimal (20+ Players)

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• Intel i5/i7 or AMD Ryzen 5/7 Based CPU
• 6 GB RAM
• 35 GB Storage Space

Building the Container

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1. Create a directory in which you will keep the Minecraft server files

# Make the folder
mkdir minecraft-server
# Ender the folder
cd minecraft-server

2. Create an environment file to be used by the Docker Container
   • The .env file allows us to specify variables used in the build process.

# Create a .env file
touch .env
# Open in a text editor
vim .env
# Enter the following variables
CONTAINER_NAME=minecraft-server
SERVER_MEM=4096 #change this to your desired value (in MB)
SERVER_JAR=minecraft_server.<version>.jar # change the version

3. Create the docker-compose.yml file
   • The docker-compose.yml file specifies the container that we want to build ³

# Create the file
touch docker-compose.yml`
# Open in a text editor
vim docker-compose.yml

version: "3"

services:
  minecraft-server:
    build:
      context: .
      args:
        SERVER_MEM: ${SERVER_MEM}
        SERVER_JAR: ${SERVER_JAR}
    volumes:
      - .server-data:/server
    ports:
      - 25565:25565
      - 25575:25575
    container_name: ${CONTAINER_NAME}
    restart: unless-stopped

volumes:
  server-data:

4. Create the Dockerfile file

   • The Dockerfile builds the container image.

# Create the file
touch Dockerfile`
# Open the file in a text editor
vim Dockerfile

FROM eclipse-temurin:17-jre

ARG SERVER_MEM
ARG SERVER_JAR

ENV SERVER_MEM=${SERVER_MEM}
ENV SERVER_JAR=${SERVER_JAR}

WORKDIR /server

CMD echo "Minecraft Server is starting\n" && java -Xms128M -Xmx${SERVER_MEM}M -jar ${SERVER_JAR} nogui

Setup the Server files

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We’re almost there, just a few steps left !!

The curious among you may have realised when trying to start the container that it fails with the error below:

Minecraft Server is starting

Error: Unable to access jarfile server.jar

This is because we have not downloaded the server jar file yet, that is our next step.

1. Navigate to one of the following sites:⁴
   • Vanilla Minecraft Server - instructions found here⁵
   • Fabric Mod loader server - instructions found here ⁶
2. Create a folder in the Minecraft-server folder called .server-data

mkdir .server-data
cd .server-data

3. Download the jar file - This will depend on the option above so read the instructions
4. Go back to the root minecraft-server folder

cd ..

5. Run the container This will create our eula.txt as well as other files needed.

docker compose up # use CTRL+C to exit

minecraft-server  | Starting net.minecraft.server.Main
minecraft-server  | [18:05:50] [ServerMain/INFO]: You need to agree to the EULA in order to run the server. Go to eula.txt for more info.
minecraft-server exited with code 0

6. Accept the EULA

# enter the .server-data folder
cd .server-data
# edit eula.txt in a text editor
vim eula.txt
# change `eula=false` to `eula=true`
eula=true

7. While in the .server-data folder make any changes you want

   • Notable files:
     • server.properties - properties like server name, game mode, world type etc…
     • ops.json - list of server operators (easier to set ingame)
     • whitelist.json - list of players allowed to join the server everyone else rejected access.

8. Run the container

# -d flag allows the container to run in detached mode i.e in the background
docker compose up -d

# monitor the logs as the server starts. CTRL+C to exit
docker logs minecraft-server --follow
# If you see the bottom line then your server is up and running
     [18:17:01] [Server thread/INFO]: Time elapsed: 25529 ms
     [18:17:01] [Server thread/INFO]: Done (34.571s)! For help, type "help"

Conclusion

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Well done you have setup a Minecraft server, now go play !!

There is a lot of cool stuff you can do from this point, for example installing mods or creating scripts to manage the server.