mc-lan-party/HOSTING.md

How to run this at the LAN party

1. Prep the modpack instance once, yourself, beforehand

1. Install Fjord Launcher Unlocked normally on your own machine.
2. Create a new instance: Minecraft 1.20.1, Forge. Name it exactly LANParty (or change INSTANCE_NAME/$InstanceName in both scripts to match).
3. Add the mods from modpack.md (use the launcher's built-in Modrinth/CurseForge browser, or drop jars straight into the instance's mods/ folder).
4. Set up the server and pregenerate first — do the "Set up the dedicated venue box" and "Pre-generate chunks before the party starts (Chunky)" steps below before continuing here. Distant Horizons can only cache real terrain that already exists; it can't backfill detail after the fact.
5. Launch the client, go to Multiplayer → Add Server, enter the venue box's LAN IP, and join for real. Set your preferred video settings (these land in options.txt). Then fly/walk around the pregenerated build area with a decent render distance and Distant Horizons enabled — this is what actually populates Distant_Horizons_server_data/ in the instance with real LOD data for that area. Quit when you've covered the zone you pregenerated.
6. Quit the launcher, then export the instance via right-click the instance → Export Instance (don't blindly zip the raw folder — the exporter lets you pick what's included). Check: mods/, config/, options.txt, servers.dat, Distant_Horizons_server_data/. Uncheck: logs/, crash-reports/, screenshots/, and any asset/library caches — those regenerate automatically on first launch and just bloat the zip. Name the result modpack.zip, with the instance's folder (LANParty/...) as the zip's top-level entry.

Caveats for this to actually pay off for participants:

• Don't rename the server list entry or change Distant Horizons' "Server Folder Name Mode" setting afterward — both are part of the cache key ("<server name> <ip>:<port>" by default). Change either and participants' clients won't find the cache you built.
• Don't regenerate/reset the server world after this point. If the actual party world differs from the one you explored, the cached LOD will show stale terrain that doesn't match reality.
• This cache is for scenery beyond render distance only — it doesn't substitute for the server having online-mode=false or for Chunky's pregen; all three pieces (pregen, DH cache, offline accounts) are independent and all need to land in the final zip/setup.

2. Set up the dedicated venue box (one machine, does both jobs)

Run server/setup-server.sh on the Linux box you're bringing to the party. It:

• Installs the Forge 1.20.1 server and wraps it in lazymc, which sleeps the real server after 5 idle minutes and transparently wakes it the instant someone connects — no manual start/stop for the whole 3 days.
• Serves server/dist/ over HTTP via a systemd unit (survives logout, auto-restarts if it dies).
• Opens the relevant ports in ufw if it's active.

cd server
./setup-server.sh
# then copy your client modpack's mod jars into mcserver/mods/, and:
sudo systemctl restart mc-lazymc

Put install.sh, install.ps1, and modpack.zip into server/dist/ (that's what gets served on port 8000).

Find the box's LAN IP (ip a) and edit the top of both install.sh and install.ps1:

• HOST_URL / $HostUrl → http://<venue-box-lan-ip>:8000
• SERVER_ADDR / $ServerAddr → <venue-box-lan-ip>:25565 (lazymc's public port)

Useful commands during the party:

• sudo systemctl status mc-lazymc — check if the MC server is asleep/awake
• sudo journalctl -u mc-lazymc -f — watch it wake/sleep live
• sudo systemctl restart mc-lazymc — pick up new mods or a config change

Resource sizing for the venue box (5–15 players)

Create is the dominant cost here — it's heavier on the server tick thread (CPU) than on RAM, because kinetic networks and contraptions get simulated every tick regardless of how many players are nearby. Farmer's Delight/its addons are cheap by comparison. Numbers below assume this modpack (~10 mods) and are total host box numbers, not just the JVM heap:

Concurrent players	JVM heap (-Xmx, set in setup-server.sh)	Host RAM (total, incl. OS + file server)	CPU	Free disk	Network
5–8	6G	10–12 GB	4 cores, 3.5 GHz+ single-core perf matters more than core count	~10 GB (world + mods + Forge libs + logs)	Gigabit LAN recommended, Wi-Fi workable
9–12	8G	12–16 GB	4–6 cores, 3.5 GHz+	~15 GB	Gigabit LAN recommended
13–15	10–12G	16 GB+	6+ cores, 3.5 GHz+	~20 GB	Gigabit LAN, wire the host box if possible

Practical knobs to turn if the box is lighter than the table:

• Lower server.properties view-distance to 6–8 — this is the single biggest CPU/RAM lever on a modded server, and the Distant Horizons client mod (see modpack.md) makes a short server view-distance look fine anyway.
• Set simulation-distance a notch below view-distance if things chug — it controls how far Create's kinetic networks/entities get ticked, independent of render range.
• MIN_RAM/MAX_RAM in setup-server.sh default to 2G/4G — bump MAX_RAM to match the table above for your headcount before running the script (or edit lazymc.toml's command line afterward and sudo systemctl restart mc-lazymc).
• An SSD matters more than raw disk size here — Create's block-entity-heavy contraptions do a lot of small, frequent chunk saves; a spinning HDD will show up as tick-time spikes.

Pre-generate chunks before the party starts (Chunky)

Chunky (server-side mod, already listed in modpack.md) fills in a radius of real terrain ahead of time so nobody hits on-the-fly generation lag while exploring. Do this once, before participants arrive:

1. Make sure mcserver/mods/ has the Chunky jar, then sudo systemctl restart mc-lazymc and let the server boot (connect once from a client, or sudo journalctl -u mc-lazymc -f and wait for "Done").

2. Run the commands below either from the server console (attach via sudo systemctl stop mc-lazymc && cd mcserver && bash run.sh nogui, temporarily bypassing lazymc so you get an interactive console) or via RCON (mcrcon -H 127.0.0.1 -P 25575 -p <password from server.properties> "<command>"):

   /chunky center 0 0        # or your build area's coordinates
   /chunky radius 800        # 800 blocks ≈ 50 chunks (1 chunk = 16 blocks)
   /chunky start
   /chunky confirm           # if it warns about area size
   

3. Watch progress with /chunky status. For ~50 chunks radius this finishes in seconds to a couple minutes depending on the box.

4. If you stopped lazymc to get console access in step 2, restart it afterward: sudo systemctl start mc-lazymc.

Repeat with /chunky world the_nether / /chunky world the_end first if you want the Nether/End build areas pregenerated too (useful since the roadmap sends people there for Nether's/End's Delight dishes).

3. Give participants the one-liner

• Windows: irm http://<your-lan-ip>:8000/install.ps1 | iex
• Linux / macOS: curl -fsSL http://<your-lan-ip>:8000/install.sh | bash

Each script asks for a nickname, derives a stable offline-mode UUID from it (so the same name = same player data across the whole 3-day party, even if they re-run the script), seeds that into a fresh accounts.json, downloads Fjord Launcher Unlocked + the modpack, and launches straight into the instance already connected to your server.

Make sure your Minecraft server itself is running with online-mode=false in server.properties — offline accounts only work against offline-mode servers.

Notes / things that can break

• The scripts pull Fjord Launcher Unlocked's latest GitHub release dynamically, so they stay correct even after version bumps — but if hero-persson/FjordLauncherUnlocked ever disappears, swap the repo slug at the top of the scripts for a current fork.
• install.sh needs curl, unzip/find (standard on any Linux/macOS box) and relies on FUSE for running the AppImage directly; if a participant's distro lacks FUSE, the AppImage will fail to launch — tell them to run ./FjordLauncher.AppImage --appimage-extract once and point LAUNCHER_BIN at the extracted AppRun.
• Re-running either script is safe/idempotent: it skips re-downloading the modpack if the instance folder already exists, and just overwrites accounts.json with the (same, deterministic) account if the nickname is unchanged.
• lazymc's first wake after a sleep takes as long as the Forge server normally does to boot (expect 20–60s depending on the box) — the client will show a "starting" MOTD/kick message during that window; just reconnect after a few seconds.
• setup-server.sh pins a Forge build (47.4.28 for 1.20.1) — check files.minecraftforge.net if it's gone stale by the time you run this.
• Double-check the server's mod list is byte-for-byte the same mods as the client instance (same versions) — Forge is strict about mod-list mismatches between client and server and will refuse to connect otherwise.