Most guides tell you to run Minecraft in a screen session and call it done. That works until the server reboots and nobody notices for three hours. Here's how to do it properly: Paper server, systemd, correct Java, memory tuning that actually matters.

Java version — get this right first

Minecraft Java edition has hard requirements:

  • Minecraft 1.21+ → Java 21
  • Minecraft 1.17–1.20 → Java 17
  • Minecraft 1.16 and older → Java 8 or 11

Running the wrong version gives you a cryptic crash at startup. Check what's installed:

java -version

Install Java 21 (Ubuntu/Debian):

sudo apt update
sudo apt install -y openjdk-21-jre-headless

If you need multiple Java versions on one server:

sudo update-alternatives --config java

Why Paper, not vanilla

Vanilla Minecraft server is fine for 2-3 players. For anything more, Paper is what you want. It's a fork that fixes hundreds of performance issues in vanilla, exposes better config options, and supports the whole Bukkit/Spigot plugin ecosystem. Nearly everyone running a public or semi-public server uses Paper.

Download the latest Paper build for your Minecraft version from papermc.io. Or grab it directly on the server:

# Replace 1.21.4 and BUILD with actual values from papermc.io
curl -o paper.jar "https://api.papermc.io/v2/projects/paper/versions/1.21.4/builds/BUILD/downloads/paper-1.21.4-BUILD.jar"

Setup

sudo useradd -r -m -d /opt/minecraft -s /bin/bash minecraft
sudo mkdir -p /opt/minecraft/server
sudo mv paper.jar /opt/minecraft/server/
sudo chown -R minecraft:minecraft /opt/minecraft

First run to generate files and accept the EULA:

sudo -u minecraft java -jar /opt/minecraft/server/paper.jar --nogui

It will exit immediately. Then:

sudo -u minecraft sed -i 's/eula=false/eula=true/' /opt/minecraft/server/eula.txt

You can't skip this. Mojang requires it.

Memory flags

The defaults are bad. Minecraft's garbage collector makes the server stutter every few seconds with default settings. Use Aikar's flags — these are widely tested and make a real difference:

java -Xms4G -Xmx4G   -XX:+UseG1GC   -XX:+ParallelRefProcEnabled   -XX:MaxGCPauseMillis=200   -XX:+UnlockExperimentalVMOptions   -XX:+DisableExplicitGC   -XX:+AlwaysPreTouch   -XX:G1NewSizePercent=30   -XX:G1MaxNewSizePercent=40   -XX:G1HeapRegionSize=8M   -XX:G1ReservePercent=20   -XX:G1HeapWastePercent=5   -XX:G1MixedGCCountTarget=4   -XX:InitiatingHeapOccupancyPercent=15   -XX:G1MixedGCLiveThresholdPercent=90   -XX:G1RSetUpdatingPauseTimePercent=5   -XX:SurvivorRatio=32   -XX:+PerfDisableSharedMem   -XX:MaxTenuringThreshold=1   -jar /opt/minecraft/server/paper.jar --nogui

Adjust -Xms and -Xmx to the same value, set to roughly 60-70% of your available RAM. Don't set them different from each other — it causes extra GC pressure. On a 8GB server, use 5G. On 16GB, use 10G.

systemd service

Create /etc/systemd/system/minecraft.service:

[Unit]
Description=Minecraft Paper Server
After=network.target

[Service]
Type=simple
User=minecraft
WorkingDirectory=/opt/minecraft/server
ExecStart=/usr/bin/java   -Xms4G -Xmx4G   -XX:+UseG1GC   -XX:+ParallelRefProcEnabled   -XX:MaxGCPauseMillis=200   -XX:+UnlockExperimentalVMOptions   -XX:+DisableExplicitGC   -XX:+AlwaysPreTouch   -XX:G1NewSizePercent=30   -XX:G1MaxNewSizePercent=40   -XX:G1HeapRegionSize=8M   -XX:G1ReservePercent=20   -XX:G1HeapWastePercent=5   -XX:G1MixedGCCountTarget=4   -XX:InitiatingHeapOccupancyPercent=15   -XX:G1MixedGCLiveThresholdPercent=90   -XX:G1RSetUpdatingPauseTimePercent=5   -XX:SurvivorRatio=32   -XX:+PerfDisableSharedMem   -XX:MaxTenuringThreshold=1   -jar /opt/minecraft/server/paper.jar --nogui
Restart=on-failure
RestartSec=10s
StartLimitBurst=3
StartLimitIntervalSec=60s

[Install]
WantedBy=multi-user.target
sudo systemctl daemon-reload
sudo systemctl enable minecraft
sudo systemctl start minecraft

Watch it start:

sudo journalctl -u minecraft -f

You'll see world generation and then Done (Xs)! when it's ready.

Firewall

sudo ufw allow 25565/tcp comment "Minecraft Java"

Default port is 25565. If you change it in server.properties, open that port instead.

server.properties worth changing

# /opt/minecraft/server/server.properties

# How many players
max-players=20

# Requires players to have a paid Minecraft account
online-mode=true

# Render distance — lower = less RAM/CPU on weak servers
view-distance=8
simulation-distance=6

# Disable if you don't want players to go to the Nether
allow-nether=true

# Message of the day
motd=§bMy Server§r §l|§r Have fun

Restart after any change: sudo systemctl restart minecraft

Console access

One thing you lose with systemd over screen: you can't type commands into the server console easily. Two options:

Use RCON — remote console built into Minecraft. Set it up in server.properties:

enable-rcon=true
rcon.port=25575
rcon.password=changeme

Then connect with mcrcon:

sudo apt install -y mcrcon
mcrcon -H localhost -P 25575 -p changeme

Or use screen for the ExecStart and attach when needed — but RCON is cleaner.

Updating Paper

sudo systemctl stop minecraft
sudo -u minecraft mv /opt/minecraft/server/paper.jar /opt/minecraft/server/paper.jar.bak
# download new paper.jar
sudo -u minecraft curl -o /opt/minecraft/server/paper.jar "https://api.papermc.io/v2/..."
sudo systemctl start minecraft

Keep the old jar around until you've confirmed the new one starts clean. Paper updates are usually painless but world corruption from a bad startup isn't.

Backup the world

Minecraft worlds live in /opt/minecraft/server/world/, world_nether/, world_the_end/. Back these up with rsync. Stop the server first or use Paper's /save-off + /save-all before rsyncing to get a consistent state.

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