Modded Minecraft server: Forge, Fabric and a CurseForge server pack

A modded Minecraft server runs the same way a vanilla one does — Java, a port, a systemd service — with one extra layer: a mod loader (Forge or Fabric) that every client and the server must run in matching versions, plus the actual mod files sitting in a mods folder the loader reads at startup. The easiest path for most packs is downloading the pack’s ready-made server pack from CurseForge or Modrinth rather than assembling the mod list by hand.

Forge or Fabric — pick what the pack already uses

You do not choose a loader independently of the modpack; the pack was built for one of them, and that decision is made for you the moment you pick a pack. The two are not interchangeable — a Forge mod will not load under Fabric or the reverse.

The fast path: a CurseForge or Modrinth server pack

Almost every published modpack has a server pack download alongside the regular client one — a zip containing the correct Forge or Fabric installer, every server-compatible mod already placed in mods/, and a ready-made start script. On CurseForge’s site, it is on the pack’s Files tab as a separate “Server Pack” download next to the client download; on Modrinth it is usually linked from the pack’s overview page. This is almost always less error-prone than rebuilding the mod list yourself, because the pack author has already filtered out client-only mods (shaders, HUD tweaks, resource pack loaders) that would crash a dedicated server or simply do nothing there.

1. 1Install Java

   Match the Java version to the Minecraft version the pack targets — current releases want Java 21, older ones (1.16 and earlier) want Java 8 or 17 depending on the exact version. Check the modpack’s own page for the Minecraft version it is built on.

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

2. 2Upload and unpack the server pack

   scp ServerFiles.zip USER@SERVER_IP:/opt/minecraft/

   sudo mkdir -p /opt/minecraft
   cd /opt/minecraft
   unzip ServerFiles.zip

   scp covers the upload in full if the server pack is large enough that a stable connection matters.

3. 3Accept the EULA

   eula=true

   Without this the server starts, prints a line pointing at Mojang’s EULA, and exits immediately — every time, on every modpack, vanilla included.

4. 4Give it enough RAM in the start script

   Most server packs ship a start.sh or a plain run.sh with the memory flags already in it; open it and raise -Xmx before the first run rather than after players complain about lag:

   java -Xms4G -Xmx6G -jar forge-1.20.1-47.2.0-shim.jar nogui

   Modded packs are the memory-hungry case the plain Minecraft server guide warns about — a heavy pack with forty or more mods routinely wants 6–10 GB where a vanilla server of the same player count runs fine on 2–4 GB. Leave headroom below the box’s total RAM for the OS and the JVM’s own off-heap memory.

5. 5Open the port and run it as a systemd service

   sudo ufw allow 25565/tcp

   [Unit]
   Description=Minecraft modded server
   After=network.target
   
   [Service]
   User=minecraft
   WorkingDirectory=/opt/minecraft
   ExecStart=/opt/minecraft/start.sh
   Restart=on-failure
   Restart=always
   
   [Install]
   WantedBy=multi-user.target

   sudo useradd -r -m -d /opt/minecraft minecraft
   sudo chown -R minecraft:minecraft /opt/minecraft
   sudo systemctl daemon-reload
   sudo systemctl enable --now minecraft

   Creating a systemd service and setting up ufw cover each step in more depth if either is new to you.

Performance: forks and settings that actually move the needle

• Server JARs aren’t interchangeable with performance forks here. Paper and Purpur (Bukkit-plugin servers) are a separate ecosystem from Forge/Fabric mods — they cannot load a Forge mod. Some packs ship a “hybrid” loader (Mohist, Arclight) that runs both Forge mods and Bukkit plugins together, at the cost of being less actively maintained than either parent project; check its own page for how current it is before relying on it.
• view-distance and simulation-distance in server.properties cost CPU and RAM per extra chunk; lowering both from the defaults is the single biggest lever on a loaded modded server, well before adding more RAM.
• Per-core speed still matters more than core count — the same ticking bottleneck that applies to vanilla Minecraft applies to every mod running inside the same tick, only with more code running per tick.

Updating mods without breaking the world

Mod versions are tied to the exact Minecraft and loader version the pack was built against. Updating a single mod to a newer release built for a different Minecraft version, without updating the whole pack, is the most common way to corrupt a world or crash the server on startup. Treat a modpack update as a unit: back up the world folder first, apply the pack author’s new server pack as a whole, and only then bring players back on. Check disk usage before a big pack update — Forge keeps old library jars around across updates, and a world with a lot of generated terrain is rarely small.

Sizing the server

These are starting points, not promises — the only reliable number is the one you measure with your own pack and player count, with Can’t keep up! in the console as the warning sign to size up. A Hi-CPU KVM instance, built around fast AMD EPYC cores rather than many slower ones, suits this kind of single-threaded-tick workload better than a plan optimised for parallel load. For the vanilla setup this guide builds on, see hosting a Minecraft server on a VPS, and for other game servers on the same box, the gaming VPS page’s sizing table covers several titles side by side.

Frequently asked