How to Fix an MC Eternal 2 Server That Keeps Crashing
MC Eternal 2 is the 1.20.1 sequel to the original MC Eternal — same kitchen-sink breadth of tech, magic, exploration, RPG combat, Create, and Ars Nouveau, but rebuilt on the modern mod ecosystem with an even bigger modlist. That breadth is exactly what makes it crash-prone on undersized or misconfigured hosting: more mods registering more world-gen, more block entities ticking, and a much higher real RAM floor than a casual guess would suggest. Here's how to work through the actual causes in order, starting with the one that kills a boot outright.
See the MC Eternal 2 pack page for the full RAM and setup breakdown before you chase anything else.
1. Wrong Java version — the most common instant-boot-failure cause
Forge on Minecraft 1.20.1 requires Java 17. It will not run on Java 8 or Java 11, and it won't downgrade gracefully — it just fails to launch. This bites people specifically when a server box was previously running an older pack like the original MC Eternal (which may have been on an earlier Minecraft version with different Java requirements) and the Java install was never updated. If your server fails before the world even starts loading, or you see Forge throw an error referencing class file versions, confirm the active Java version is 17 before you look at anything else.
- Check the Java version the server process is actually launching with, not just what's installed system-wide
- If multiple Java versions exist on the host, make sure the start script points at the Java 17 binary specifically
2. Create contraptions causing gradual tick lag, not an instant crash
If your server boots fine and runs smoothly for a while before TPS starts sliding, Create is the first mod worth looking at in a pack this size. Factory-scale contraptions — large rotational power networks, long conveyor belt lines, big mixer or press setups — are a well-documented source of tick lag in any modern kitchen-sink pack that includes Create, and MC Eternal 2 is squarely that kind of pack. The lag tends to scale with how much players have actually built, which is why it often shows up days or weeks into a server's life rather than on day one.
Use a profiler like spark to confirm whether Create's tick functions are actually dominating the tick time before assuming it's something else.
3. First-chunk-load lag spikes when exploring new terrain
A modlist as broad as MC Eternal 2's registers a large number of world-generation features — biomes, structures, ore distributions, and dimension-specific generation from the tech, magic, and exploration mods all layering on top of each other. The first time any player walks into a chunk that hasn't been generated yet, the server has to run all of that generation at once, which can produce a sharp, short lag spike or even a tick timeout on a server that's already running close to its resource limit. This is usually mistaken for a random crash, but it's really a predictable cost of exploring unexplored terrain in a pack this dense.
4. Mod conflicts and config corruption after a mid-save update
Updating individual mods or changing config files on an existing MC Eternal 2 world carries real risk in a pack this size — the mod count alone means a higher chance that two mods' config changes interact badly, or that a config file gets partially written if the server was stopped mid-save during an update. If crashes started appearing right after a modpack update or a manual config edit rather than during normal play, that's a strong signal the problem is a specific config or mod-version mismatch rather than a resource issue, and it's worth reverting to a backup taken before the change to confirm.
5. RAM under the pack's realistic floor
10 GB is the real floor for MC Eternal 2, and that's higher than what the pack's breadth alone might suggest if you're comparing it to a smaller kitchen-sink pack. Running below that floor rarely produces a clean, instant out-of-memory crash — what you'll actually see is cascading lag first: garbage collection pauses get longer and more frequent as the heap fills up, TPS drifts down in a sawtooth pattern, and eventually the server hits a tick timeout and the watchdog kills the process, which can look identical to a Create tick-lag crash or a world-gen spike if you're not watching memory at the same time. If crashes correlate with uptime (worse the longer the server has been running) rather than with a specific action, check actual heap usage before assuming it's a mod conflict.
FAQ
Why does my MC Eternal 2 server crash immediately on boot, before any players even join?+
An instant boot failure almost always points to the Java version, not the modpack config. MC Eternal 2 runs Forge on Minecraft 1.20.1, which requires Java 17 — if the host (or a leftover install from an older pack) is still running Java 8 or Java 11, Forge will fail to initialize before the world even loads. Check the server's Java version first before touching any mod files.
The server runs fine for a while, then TPS tanks and it eventually crashes. What's causing that?+
This is the classic signature of accumulated tick lag rather than a hard crash from a single mod. In a kitchen-sink pack this broad, the most common contributor is Create: large factory-scale contraptions with a lot of rotational power or conveyor belts add real per-tick cost, and that cost compounds as players build more of them. If TPS degrades gradually rather than dropping instantly, look at what's been built with Create before assuming a different mod is at fault.
How much RAM does MC Eternal 2 actually need to run reliably?+
10 GB is the real floor for MC Eternal 2 on a live server, not the 6-8 GB a generic kitchen-sink guess might suggest. This pack has a notably bigger modlist than the original MC Eternal, spanning tech, magic, exploration, RPG combat, Create, and Ars Nouveau at once, and all of that adds up in loaded class data and world state well beyond what a smaller pack of the same era needs.
Host MC Eternal 2 on hardware sized for its real floor
MC Eternal 2's real RAM floor is 10 GB, not a generic kitchen-sink guess, and before any risky config change or mod update it's worth taking a backup so a bad edit is a quick rollback instead of a lost world.
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