How to run an All the Mods (ATM) server

All the Mods is the reference "kitchen-sink" modpack: around 500 mods in version 10, tech through magic, and over 21 million downloads on CurseForge. It's also one of the heaviest packs to host. Here's what it actually demands, and the three things that sink an ATM server.

Which version, and why it matters

ATM ships one generation per Minecraft version (ATM8, ATM9, ATM10…), and they aren't interchangeable. The latest, All the Mods 10, targets Minecraft 1.21.1 on the NeoForge loader.

The loader has changed across generations — the modded Minecraft ecosystem moved from Forge to NeoForge, and each ATM generation follows whichever was current. You don't have to pick it: the pack imposes it, and it's installed for you. Do check which generation you're launching on the pack's page, then make sure your players install exactly the same version, or the connection is refused.

Choose the version by what your group wants to play, not by novelty: an ATM run lasts months, and you don't migrate an ATM world across major versions.

RAM: the real number, and why 8 GB isn't enough

This is what costs everyone their evenings, and it's badly explained everywhere.

When you read "ATM wants 8 GB", that means the JVM heap (-Xmx) — not the machine's memory. The two are never equal: the operating system, Docker and Java's off-heap memory live beside the heap. Here, the heap is the smaller of "RAM − 2 GB" and "75% of RAM":

In other words: take the 16 GB tier. The 8 GB tier yields only a 6 GB heap, and a 500-mod pack survives startup on it then dies the moment someone explores. That's why the creation screen warns you if you go below — it compares heaps, not machine sizes.

Note carefully: CurseForge states no official RAM figure for ATM10. The tier above is what we recommend for this pack, not a recommendation from its authors.

CPU, the other half of the problem

A 500-mod pack doesn't only cost memory: it costs compute per tick. Hundreds of Create machines running, pipes, AE2 automation — all of it has to be simulated twenty times a second.

The symptom is distinct from a memory one: the server doesn't fall over, it drags. Blocks take a second to react, mobs stutter, machines slow down. If the heap is comfortable and it still drags, RAM is no longer the issue: move to the dedicated CPU level, the only change that lifts ticks per second.

The first boot takes twenty minutes

Five hundred mods have to be downloaded, resolved, and written out as hundreds of configuration files — then a world crammed with added structures and biomes has to be generated. Expect 15 to 25 minutes on first boot. A vanilla server is ready in two minutes; don't compare the two.

This is the classic phantom failure: people assume it crashed, kill it, start over — and never finish that first boot. Let it run to the end, once. The later ones are fast.

The three ways an ATM server fails

A different pack version client-side. The most frequent by far. Check the version number, not the name: "All the Mods 10" exists in dozens of builds.

Too small a heap. The server starts, holds at spawn, then dies when a player wanders off. Generating modded chunks is the most memory-hungry thing it does.

An ATM world loaded without ATM. A world from this pack contains thousands of blocks Minecraft has never heard of. Loaded without its mods — or with a different major version of the pack — it loses them permanently. Never switch packs on an existing world: create a second server.

What's kept

The data directory is archived before every shutdown, with a save-all flush immediately before, and restored on the next boot. An automatic backup runs every 30 minutes while you play, of which the last 5 are kept. Storage is free, server off included.

What isn't archived: the server's libraries and binaries, re-downloaded each session. Your archive holds only your world, your configuration and your mods.

Why a big pack by the hour changes the maths

ATM is precisely where by-the-hour billing pays off most, exactly because it demands a big machine.

A monthly subscription for 16 GB costs full price whether you play or not. By the hour, the same machine costs €0.05/h: three evenings of three hours a week, about 36 hours a month, comes to €1.80. And with the server off it's €0 — where a 16 GB machine left running is paid for in full, played or not.

It's the one case where "big modpack" and "small budget" hold together.

Create your Minecraft server and paste in the All the Mods link. Your first session is free.