How to Fix an ATM9 To the Sky Server That Keeps Crashing
All the Mods 9 - To the Sky runs the full ATM9 mod list on a custom skyblock start — same tech tree, same tick pressure, just no ground under it. The pack's own community support flow treats most crashes as a RAM problem first; here's that check plus the three things worth ruling out next.
See the ATM9 To the Sky pack page for sizing before you chase anything else.
1. RAM — the pack's own first troubleshooting step
The All the Mods Discord's own FAQ sends crash reports straight to the #bot-spam channel's ?allocate command before anyone looks at a log. That's not a brush-off — ATM9SKY shares ATM9's full mod list, and the same Refined Storage / tech-tree RAM pressure applies the moment a base is running, skyblock start or not.
If you haven't already, allocate well above whatever a vanilla or lightly-modded server would need. ATM-family packs this size want double-digit gigabytes once a real base exists, not the 4-6 GB that gets a fresh island through its first few minutes.
2. A too-low default JVM range in Docker
Several published ATM9SKY container images default to a JVM heap as low as -Xms2048m -Xmx4096m. That's enough to boot an empty skyblock platform and crash a few minutes later once chests, machines and the Refined Storage network start filling in.
Check your actual running -Xmx value directly — a host with plenty of free RAM doesn't help if the container's own JVM flags cap it artificially low.
3. Startup instability from the custom skyblock dimension
The skyblock start chunk is a custom structure, not vanilla world-gen — a corrupted or partially-generated start platform can throw errors on the very first boot that look like a mod conflict but are actually a world-gen problem specific to the sky variant.
If the crash happens on the first-ever boot before any player has even spawned, regenerating the world from a clean copy of the pack's server files (rather than troubleshooting mods) is usually faster.
4. The same tech-tree causes as base ATM9
Once the island has a running base, ATM9SKY inherits every crash class the ground version has — Refined Storage networks that overflow on load, ticks that run long from autocrafting loops, and GC pauses that look like lag before a real crash. Treat it as ATM9 with a different starting screen, not a separate pack to diagnose from scratch.
FAQ
Is All the Mods 9 - To the Sky the same mod list as base ATM9?+
Yes — ATM9SKY runs the same NeoForge mod set as All the Mods 9, just with a custom skyblock start dimension instead of a normal world. That means the same tech-tree crashes and the same RAM pressure as base ATM9 apply here too, not a lighter load just because it starts on an island.
What does the official ATM9 support channel say to do first?+
The pack's own FAQ and Discord bot direct players to the #bot-spam channel's ?allocate command as the first troubleshooting step, before touching logs or configs — RAM is the single most common cause they see.
Why does a Docker-hosted ATM9SKY server crash when a self-hosted one doesn't?+
Several published ATM9SKY Docker images ship a default JVM range as low as -Xms2048m -Xmx4096m — enough to boot an empty skyblock island but not enough once a tech-tree base is running. Check your container's actual -Xmx value, not just the RAM the host machine has.
Host ATM9 To the Sky with the RAM it actually needs
CoalHost sizes ATM-family servers well above the Docker-default minimum from the first boot, with backups in place before any world-gen retry.
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