Better MC Server Setup: Installing BMC4 or BMC5 on Your Server

Better MC is Luna Pixel Studios' "vanilla+" modpack: about 350 mods on the server side that expand normal Minecraft rather than replace it. Its community is r/betterminecraft, so a "Better Minecraft server" usually means this pack. There are two live versions, on different Minecraft versions and different loaders, and the first job in setting up a server is picking one.

This guide covers both: which to choose, how to install the official server pack on a GameServerKings server, which files in the pack you can ignore, and what to check when players can't join.

BMC4 or BMC5?

BMC4 has by far the larger player base on CurseForge (about 18 million downloads against about 3 million for BMC5), so it's the easier choice if your friends already have it installed. BMC5 is the one on the newer Minecraft version. Both need a matching client, so settle this with your players before you install anything.

Installing the Server Pack

1. Set the loader in the panel

Back up the server first if it has anything you want to keep (How to create a backup). Then, in the Startup tab:

Then run Reinstall from the Settings tab. The install script downloads the loader and keeps worlds, mods/, config/ and server.properties.

The script chooses the loader build itself, and the Build Number variable doesn't change it for Forge or NeoForge:

• BMC4: the script installs Forge's recommended build for 1.20.1, 47.4.10, which is older than the pack's 47.4.20.
• BMC5: it installs the newest non-beta NeoForge for 1.21.1 (21.1.252 when we checked), one step ahead of the pack's 21.1.250.

We haven't booted either pack on these builds ourselves. If the pack refuses to start, the console names the build it wants. Contact support with that build number and we'll help you get it installed.

2. Download the server pack

Open the pack's CurseForge page (BMC4 or BMC5), go to Files, click the exact version your players have, and download the server pack from that file's Additional Files. The CurseForge app doesn't download server packs, so use the website.

3. Upload and unpack

Both server packs are far over the 100 MB browser-upload limit on most of our nodes. Upload the zip over SFTP on port 2022 (How to upload files via SFTP), then open the zip's menu in the Files tab and choose Unarchive. The pack unpacks straight into the server root. Delete the zip afterwards.

4. Know which files do nothing here

Both packs are built with ServerPackCreator. They ship scripts that download Java and install the loader on a home PC, via NeoForged's ServerStarterJar. The panel does both jobs itself, so these files are never used on our servers:

• start.sh, start.bat, start.ps1, install_java.sh, install_java.ps1
• variables.txt (including its -Xmx4G: memory comes from your plan, see below)
• HOW-TO-RUN.md and manifest.json
• BMC4 only: a partial libraries/ folder, logs/, and a forge-1.20.1-47.4.20-installer.jar.log left over from the pack author's own test run

You can delete them or leave them. Don't delete mods/, config/, defaultconfigs/ or datapacks/. Better MC ships compatibility datapacks in datapacks/, plus (in BMC5) config/paxi/datapacks/ for the Paxi mod the pack includes.

5. Start

Server started life on Paper?

New servers start on Paper. If you keep a world Paper created, the first modded start can fail with Missing data pack paper. Set Extra Flags to --safeMode, start once, stop, and clear Extra Flags. With a pack this size, a fresh world is usually the cleaner start.

Start the server and watch the Console. Players connect with the same Better MC version from the CurseForge app (or Prism).

Memory for Better MC

Both server packs set -Xmx4G: the author runs the server with a 4 GB heap. On our servers the startup command uses -XX:MaxRAMPercentage=95.0, so the heap is 95% of your plan's RAM, and variables.txt has no effect. A plan with a bit more than 4 GB matches the pack's own setting. Add more for larger groups, because every player keeps their own area of the world loaded. Minecraft Server RAM and JVM Flags covers sizing, and OutOfMemoryError: Java heap space covers what running short looks like.

Updating to a New Better MC Release

Better MC updates about monthly. For each update:

1. Back up and stop the server.
2. Delete mods/, then unpack the new server pack over the server. A clean mods/ avoids leftover jars from the old version.
3. If you changed any configs yourself, re-apply them. The new pack's config/ replaces yours.
4. Check the new variables.txt for MODLOADER_VERSION. If the loader changed, reinstall from Settings.
5. Start, then tell players to update. Anyone still on the old version will be refused.

If an update drops a mod, its blocks and items disappear from the world. Missing Mods in World explains why.

Troubleshooting

• Players get a mod-list or channel mismatch. The client and server are on different Better MC versions, or one side is BMC4 and the other BMC5. See Mismatched mod channel list.
• The server stops at once with a Java error. The Docker image doesn't match: Java 17 for BMC4, Java 21 for BMC5. Change it and restart. No reinstall is needed.
• The server boots but the world looks vanilla. Framework is still PAPER, or mods/ didn't unpack. Check both.
• Can't keep up! while players explore. Generating new terrain is often the cause. See Can't keep up! and pre-generate with the tools in World Management.
• Something else in the log. Work through Reading Minecraft Server Logs and Crash Reports.

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