SciCraft/docs/server.md

Server — Properties, JVM, Operations

Three server tiers are provided as drop-in presets in presets/<tier>/server/ (see presets/README.md). The Medium tier is the recommended default.

Tier	Host RAM	view-distance	simulation-distance	max-players
Low	8-16 GB	5	4	8
Medium	16-32 GB	8	6	8
High	32 GB+	12	10	16

Apply a tier (after packwiz install):

cp presets/medium/server/server.properties server_pack/server.properties
# then use the matching jvm-flags.txt when launching

server_pack/eula.txt → eula=true (after review).

Recommended JVM Flags (server, Medium)

java -Xms4G -Xmx8G \
  -XX:+UseG1GC \
  -XX:+ParallelRefProcEnabled \
  -XX:MaxGCPauseMillis=200 \
  -XX:+UnlockExperimentalVMOptions \
  -XX:+DisableExplicitGC \
  -XX:+AlwaysPreTouch \
  -XX:G1NewSizePercent=30 \
  -XX:G1MaxNewSizePercent=40 \
  -XX:G1HeapRegionSize=8M \
  -XX:G1ReservePercent=20 \
  -XX:G1HeapWastePercent=5 \
  -XX:G1MixedGCCountTarget=4 \
  -XX:InitiatingHeapOccupancyPercent=15 \
  -XX:G1MixedGCLiveThresholdPercent=90 \
  -XX:G1RSetUpdatingPauseTimePercent=5 \
  -Dlog4j2.formatMsgNoLookups=true \
  -jar neoforge-21.1.248-server.jar nogui

Notes:

• G1 tuning keeps large-tech-server TPS stable under chunk gen (Krypton Reno + BadOptimizations help server-side).
• -Xms4G avoids early GC churn. Cap at 8G for Medium; this pack is RAM-hungry from AE2/Mekanism tick load but Medium does not need 16G.
• See presets/low/server/jvm-flags.txt (2-4G) and presets/high/server/jvm-flags.txt (8-16G) for the other tiers.

Server start order

1. packwiz install --dir server_pack (first time / after changes)
2. Accept EULA.
3. Launch with the JVM flags above.

Common failures

Symptom	Fix
"Mismatched mods" on client join	Run packwiz refresh both packs, redeploy.
Sinytra connector errors	Update Sinytra Connector + Forgified Fabric API together.
Iris black screen	Disable flywheel compat first, then test without shaders.
Crash on world gen (Deeper and Darker)	Ensure CF 659011 + its lithostitched data load; update both.
TPS lag from many AE2 cells	Check FTB chunk claims; lower simulation-distance.
Immersive Portals won't load	Must be the Fabric jar added via url add --force (Modrinth blocks loader mismatch).
Server boots with OLD mod set after a pack update	packwiz-installer -g only disables the GUI — it does NOT refresh metadata. Freshness comes from which pack.toml it reads: if the panel cloned the repo, git pull (or wipe + re-clone) before restart; the start script prefers a local server_pack/pack.toml over the remote URL. Verify with python3 tools/validate_pack.py server_pack remote.
EntityLMixin / worldportal crash on boot	The pack ships a patched World Portal (tools/patches/); make sure mods/worldportal-neoforge-0.0.10+1.21-patched.jar is what actually landed (see stale-metadata row above).
KubeJS Wrapper for class ...ProcessingOutput already exists!	Pack ships a patched Create Ore Excavation (tools/patches/build_patched_coe.sh) that removes its duplicate rhino wrapper; upstream race between COE and kubejs-create mod-construction order. Verify the -patched.jar landed (see stale-metadata row above).

Patched jars in this pack

Two mods ship as locally patched jars under tools/patches/; both are referenced by mods/*.pw.toml via raw git URLs, so the jars must be pushed for any fresh install to work:

Jar	Patch	Reproduce with
worldportal-neoforge-0.0.10+1.21-patched.jar	Removes EntityLMixin (conflicts with Sable mixins)	hand-patched; see commit a88a0c2
createoreexcavation-1.21-1.6.8-patched.jar	Strips COE's guarded ProcessingOutput wrapper registration (race vs kubejs-create)	bash tools/patches/build_patched_coe.sh

After changing either: update the hash in both packs' mods/<name>.pw.toml, run packwiz refresh, then python3 tools/validate_pack.py <pack> remote.

Backups

• World: copy server_pack/world/ (or use FTB Chunks backups).
• Configs: server_pack/config/ mirrors client defaults; keep both in sync when changing KubeJS scripts or FTB settings.