// modpack server guide
Mustard Virus server hosting & setup guide
A Mustard Virus server needs Java 8 and about 2.5–4 GB of RAM for up to 8 players.
The Mustard Virus has gone global and wiped out humanity. You're all that remains, well - you and the endless waves of infected. How long can you last? Will your base be strong enough to stop the horde?
Summary from Mustard Virus on Modrinth.
Mustard Virus is a Forge modpack for Minecraft 1.12.2 with 47 mods. We'd pick our Standard plan (4 GB) for it.
Quick facts
| Loader | Forge |
|---|---|
| Minecraft versions | 1.12.2 |
| Java needed | Java 8 for Minecraft 1.12.2 Java version chart. |
| Mods | 47 modsCounted from the pack's file list on Modrinth. None are marked client-only. |
| RAM | About 2.5–3 GB for 1–3 playersBy player count. |
| Downloads | 149,613 on Modrinth |
| Last updated | February 22, 2024 (version 2.2.0) |
| First published | February 18, 2024 on Modrinth |
| Server support | Required: the pack has mods that must run on the server. |
| Server pack | Not published separatelyHow to build the server. |
| Modrinth tags | adventure, challenging, combat |
Mustard Virus server files
No. Mustard Virus has no separate server pack on Modrinth, so the server is built from the .mrpack: the Forge server for Minecraft 1.12.2, plus the pack's overrides folder and the server-side mods its modrinth.index.json lists. A modpack installer does this for you; our guide shows how to make a server for a modpack with no server pack.
How much RAM does a Mustard Virus server need?
| Players online | RAM | DSN plan |
|---|---|---|
| 1–3 players | About 2.5–3 GB | Standard (4 GB) |
| 4–8 players | About 2.5–4 GB | Standard (4 GB) |
| 9–15 players | About 3.5–5 GB | Premium (8 GB)Standard (4 GB) can do if players stay close. |
Estimated from 47 mods on the server with our RAM calculator, not measured: low end if players stay together, high end if they spread out.
Set Java's heap (-Xmx) 10–15% under the RAM you have, about -Xmx3500M on 4 GB. Forge 1.12.2 takes it in the java command (-Xmx), usually in the start script. RAM guide.
Mustard Virus server requirements
| Java | Java 8 |
|---|---|
| Loader | Forge for Minecraft 1.12.2 |
| CPU | Fast single-core speed (one main thread). |
| RAM | About 2.5–5 GB for 1–15 players (table above) |
| Disk | The server files, a growing world and backups |
| Network | TCP port 25565 open to players |
Recommended plan
Our pick for Mustard Virus
Standard
4 GB RAM · planned launch price $16/month
At about 47 Forge mods this is a light pack, so 4 GB of RAM covers it for a small group.
Ordering is closed until we relaunch. We aren't taking orders or payments while we move to new hardware. Join the launch list and we'll email you when Standard servers open.
More than 8 players, or lots exploring at once? Go up to Premium (8 GB). Not sure? Email hello@dsnservers.com.
Planned launch price in USD, billed monthly once ordering opens, with a 7-day refund window.
How to make a Mustard Virus server on your own PC
What's specific to Mustard Virus, step by step. The full walkthrough for any pack: how to make a modded Minecraft server.
- Install Java 8.
Check with
java -version. Java version chart. - Get the server files.
Build them from the .mrpack, as in server files above.
- Start it and accept the EULA.
Run the start script in the server files, or
java -jaron the Forge jar the installer made, then seteula=trueineula.txtif you accept Mojang's EULA (EULA step). - Set the RAM with
-Xmx, sized from the table above. - Let friends connect: forward TCP 25565, or use a tunnel or host behind CGNAT (can't connect?).
Or run Mustard Virus on DSN
Once we relaunch (join the launch list), on DSN you'd install Mustard Virus from the panel's Modrinth modpack installer (version 2.2.0), pick Java 8 on the Startup tab and accept the EULA in the console. No port forwarding.
How to play Mustard Virus with friends
Each player installs Mustard Virus version 2.2.0 with the Modrinth App or Prism Launcher, the same version as the server, and adds the server's address under Multiplayer.
Different versions of Mustard Virus on the server and a client show up as Mismatched mod channel list or mod rejections. Why friends can't join, timeouts included.
Lag and performance on Mustard Virus
Can't keep up! Is the server overloaded? means ticks take longer than 50 ms; more RAM won't fix that once Mustard Virus has enough (tick lag guide). For Mustard Virus:
- Distances:
view-distance=8inserver.properties. - Pre-generate: with a pregeneration mod built for 1.12.2, before people explore.
Common Mustard Virus crashes
What a Forge 1.12.2 server running Mustard Virus hits most. For any other error, paste the log into the free crash log analyzer.
- Wrong Java version. Forge for 1.12.2 won't start on anything newer than Java 8, and stops with
ClassCastException: class jdk.internal.loader.ClassLoaders$AppClassLoader cannot be cast to class java.net.URLClassLoader. Java version fix. - Out of memory. Mustard Virus (47 mods on the server) needs about 2.5–3 GB for 1–3 players;
java.lang.OutOfMemoryErrormeans it ran out. Out-of-memory fix. - Client-only mod on the server. The Mustard Virus pack file marks none of its mods client-only, so this usually means one was copied over from a player's mods folder. Check a mods list with the client-or-server-side checker. Client-only mod fix.
- After adding or updating a mod. Mods you add to Mustard Virus by hand usually crash it with a missing dependency:
net.minecraftforge.fml.common.MissingModsExceptionnames the mod. - Ticking entity or block entity. The crash report names it and gives its coordinates. Ticking entity fix.
Updates and support
Before moving Mustard Virus past version 2.2.0, back up the world: see updating a modpack server without losing your world.
Bugs in Mustard Virus itself go to its authors: Discord. Server problems on DSN: hello@dsnservers.com or Discord.
Packs like Mustard Virus
More: all modpack guides and how to make a modded server.
Run Mustard Virus on DSN when we relaunch.
Our pick, Standard: 4 GB, planned at $16/month.
DSN Servers isn't affiliated with Mustard Virus or Modrinth. The pack's name, icon, summary and stats come from Modrinth's public API (checked October 4, 2026).