// modpack server guide

One Block ModPack server hosting & setup guide

A One Block ModPack server needs Java 21 and about 2–3.5 GB of RAM for up to 15 players.

A lightweight OneBlock-based modpack that lets you start on a single regenerating block and build your world from nothing. Includes extra performance mods for smoother gameplay and better stability.

Summary from One Block ModPack on Modrinth.

By DSN Servers · Updated October 2026 · Fabric · Minecraft 1.21.10 · Java Edition

One Block ModPack is a Fabric modpack for Minecraft 1.21.10 with 12 mods. We'd pick our Standard plan (4 GB) for it.

Quick facts

Loader	Fabric
Minecraft versions	1.21.10
Java needed	Java 21 for Minecraft 1.21.10 Java version chart.
Mods	12 modsCounted from the pack's file list on Modrinth. None are marked client-only.
RAM	About 2 GB for 1–3 playersBy player count.
Downloads	119,525 on Modrinth
Last updated	November 30, 2025 (version 1.0.0)
First published	November 30, 2025 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, lightweight

One Block ModPack server files

No. One Block ModPack has no separate server pack on Modrinth, so the server is built from the .mrpack: the Fabric server for Minecraft 1.21.10, 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 One Block ModPack server need?

Players online	RAM	DSN plan
1–3 players	About 2 GB	Standard (4 GB)
4–8 players	About 2–2.5 GB	Standard (4 GB)
9–15 players	About 2–3.5 GB	Standard (4 GB)

Estimated from 12 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. Fabric 1.21.10 takes it in the java command (-Xmx), usually in the start script. RAM guide.

One Block ModPack server requirements

Java	Java 21
Loader	Fabric for Minecraft 1.21.10
CPU	Fast single-core speed (one main thread).
RAM	About 2–3.5 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 One Block ModPack

Standard

4 GB RAM · planned launch price $16/month

At about 12 Fabric 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.

Join the launch list Compare all plans

More than 15 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 One Block ModPack server on your own PC

What's specific to One Block ModPack, step by step. The full walkthrough for any pack: how to make a modded Minecraft server.

Install Java 21.
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 -jar on the Fabric 1.21.10 server launcher, then set eula=true in eula.txt if 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 One Block ModPack on DSN

Once we relaunch (join the launch list), on DSN you'd install One Block ModPack from the panel's Modrinth modpack installer (version 1.0.0), pick Java 21 on the Startup tab and accept the EULA in the console. No port forwarding.

How to play One Block ModPack with friends

Each player installs One Block ModPack version 1.0.0 with the Modrinth App or Prism Launcher, the same version as the server, and adds the server's address under Multiplayer.

Different versions of One Block ModPack 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 One Block ModPack

Can't keep up! Is the server overloaded? means ticks take longer than 50 ms; more RAM won't fix that once One Block ModPack has enough (tick lag guide). For One Block ModPack:

Measure first: spark's /spark tps and profiler work on 1.21.10 and name the mod or machine using the tick time.
Distances: view-distance=8 and a lower simulation-distance in server.properties.
Pre-generate: Chunky for 1.21.10, /chunky radius 3000 then /chunky start, before people explore.

Common One Block ModPack crashes

What a Fabric 1.21.10 server running One Block ModPack hits most. For any other error, paste the log into the free crash log analyzer.

Wrong Java version. One Block ModPack on Minecraft 1.21.10 needs Java 21. Started on Java 17, it stops with UnsupportedClassVersionError: ... class file version 65.0, this version of the Java Runtime only recognizes class file versions up to 61.0. Java version fix.
Out of memory. One Block ModPack (12 mods on the server) needs about 2 GB for 1–3 players; java.lang.OutOfMemoryError means it ran out. Out-of-memory fix.
Client-only mod on the server. The One Block ModPack 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 One Block ModPack by hand usually crash it with a missing dependency or a mixin conflict.
Ticking entity or block entity. The crash report names it and gives its coordinates. Ticking entity fix.

Updates and support

Before moving One Block ModPack past version 1.0.0, back up the world: see updating a modpack server without losing your world.

Bugs in One Block ModPack itself go to its authors through its Modrinth page. Server problems on DSN: hello@dsnservers.com or Discord.

More: all modpack guides and how to make a modded server.

Run One Block ModPack on DSN when we relaunch.

Our pick, Standard: 4 GB, planned at $16/month.

Join the launch list

DSN Servers isn't affiliated with One Block ModPack or Modrinth. The pack's name, icon, summary and stats come from Modrinth's public API (checked October 4, 2026).