Set up a Fabric Minecraft server at VeryCloud

Introduction

Fabric emerged as a leaner alternative to Forge. On Minecraft 1.16+, Fabric is often the better choice for performance and stability over compatibility with aging heavy modpacks.

Prerequisites

• A VeryCloud Minecraft server (any starting image, we replace)
• Access to Wisp Files and Startup
• Target Minecraft version (1.20.4, 1.21.x, etc.)

Step 1: Backup first

1. Panel → Backups → Create Backup
2. Name: pre-fabric-switch-2026-05
3. Wait for Complete

Step 2: Download Fabric server installer

Go to https://fabricmc.net/use/server/

Select Game version, Loader version (latest stable), Installer version (latest), then Download Server JAR.

You get fabric-server-mc.X.Y.Z-loader.A.B.C-installer.D.E.F.jar.

Step 3: Upload

In Wisp → Files:

1. Rename to fabric-server-launch.jar
2. Upload at the container root
3. If a server.jar exists, rename to server.jar.old

Step 4: Configure startup

In Startup:

1. Set SERVER_JARFILE → fabric-server-launch.jar
2. Check VERSION matches the installer
3. JAVA_VERSION: MC 1.20+ needs Java 17+, MC 1.21 needs Java 21
4. Save

Step 5: First boot

Restart. First boot Fabric:

• Downloads the matching Vanilla server.jar if needed
• Generates fabric-server-launcher.properties
• Creates the world

If eula.txt is false, set it to true and restart.

Step 6: Install Fabric mods

Mods go in /mods/. Sources:

• Modrinth — modern repo
• CurseForge — filter Fabric

Recommended performance mods:

⚠️ Match exact Minecraft + Fabric Loader version. A 1.20.1 mod won't work on 1.20.4.

Step 7: Fabric API (required for 95% of mods)

Download fabric-api-X.Y.Z+1.21.jar from https://modrinth.com/mod/fabric-api, upload to /mods/, restart.

Without Fabric API, most mods crash at boot.

Step 8: Configure mods

Configs land in /config/ per mod. Lithium and Starlight are zero-config. Edit as needed for others.

Step 9: Test performance

Install spark (https://spark.lucko.me/) for profiling:

/spark profiler start
# 60 seconds of gameplay
/spark profiler stop

You should see stable 20.0 TPS even with 30+ players, ~25-30% RAM reduction, 10x faster light propagation.

Troubleshooting

Crash with version mismatch — all mods must match MC + Fabric Loader version. Remove mods one by one. Mixin error — two mods patching the same class. Crash report indicates which. Performance not better — verify mods are active with /spark health. Profile to find the real bottleneck. Slow worldgen — install C2ME, combine with pregen (Chunky / Chunk-Pregenerator).

Useful commands

/spark profiler start
/spark profiler stop
/spark tps
/forceload add <x> <z>

Conclusion

Fabric is the modern choice for an optimized Minecraft server: lighter than Forge, quality performance mods, fast updates after Vanilla releases. 15 minutes for install at VeryCloud with a clean performance mod setup.

Going further: modpack via Quilt, Modrinth API for auto-updates, spark + Grafana profiling.

Resources

• Fabric — Official
• Modrinth Fabric mods
• spark
• Lithium GitHub