Set up the Crucial 2 modpack server

Crucial 2 is a Forge modpack for Minecraft 1.16.5 by Vazkii. Its CurseForge page calls it a vanilla-styled pack with only high quality mods tuned to play together, and it puts a guide book in your inventory in survival. This guide installs it from the pack's client file, because the server download on CurseForge does not contain the mods.

Checked against Crucial 2 1.5 (the CurseForge file dated 13 October 2023) on Forge 36.2.39 and Minecraft 1.16.5, October 2026.

Why this pack installs from the client file

When a CurseForge pack lists a server pack, the Modpacks tab installs that. Crucial 2 publishes a server download of about 1.1 MB, Crucial2-1.5-server-hotfix.zip. It holds configs and scripts plus a mods.csv list and setup scripts that download the mods when you run them on your own computer. The panel does not run those scripts, so installing Crucial 2 from the CurseForge search would give you a Forge server without the pack's mods.

The client file, Crucial2-1.5.zip, is different. It is a list of the pack's mods plus its configs and scripts. The panel can read that list, download each mod and add the configs, the same way it handles other CurseForge packs that have no server pack.

What the pack needs

• Minecraft 1.16.5 with Forge 36.2.39. The panel reads both from the client file's mod list. The pack's server readme says Java 8 is required and newer Java will not work. The panel picks Java 8 for 1.16.5, as the next section shows.
• Memory. The CurseForge page gives no figure, and the server readme gives no recommended amount (its troubleshooting command uses a 3 GB heap, -Xmx3G). Read how much RAM a Minecraft server needs and check the Minecraft plans before you install.
• A file on your computer. Download Crucial2-1.5.zip, about 13 MB, from the Files tab of the Crucial 2 page on CurseForge. Pick the main file, not the one named server hotfix.
• Disk space. The installer downloads about 240 MB of mods on top of the pack file.
• The same pack version for players. This guide installs 1.5, the newest version on the CurseForge page. Players should run that version.

Switch the server to Forge 1.16.5 first

1. Open your server and choose JAR Manager under More in the left rail.
2. Under Server software, pick Forge. Under Minecraft version, pick 1.16.5.
3. Press Apply change. Leave Take a backup first ticked and hold Confirm & reinstall until it fills. Wait for the install to finish.

For Minecraft 1.16.5 the panel sets the server to Java 8, and the pack install that follows keeps that setting.

Install the pack

1. Open your server and choose Modpacks under Content in the left rail. If there is no Install your own pack card, that option is not switched on for your account yet. Contact support and name this pack.
2. In the Install your own pack card, drop Crucial2-1.5.zip onto the box that says Drop a .mrpack or a server-pack .zip. Nothing installs until you press the install button.
3. Leave Take a backup first ticked. Tick Keep my world, settings and player lists only if you want to keep the world you have now. Otherwise the pack's world replaces it.
4. Press Install and reinstall, then hold the confirm button in the window that opens.
5. Open the Console and watch the install. The pack's list has 156 mods.

When this guide was checked, 140 of them came straight from CurseForge or Modrinth. The panel left out 15 client-only mods, such as Embeddium and Mouse Tweaks, because Modrinth marks them as unsupported on servers. One mod, Mirabilis: Biome Overhaul, only allows downloads from CurseForge's own site, so the panel cannot add it for you. Once the install ends, the Modpacks tab shows a warning under the installed pack that names the mod. It has a Download from CurseForge button and a box to drop the downloaded file onto, and when the last mod is in the panel offers Restart now. Modpack mods to download from CurseForge covers that step.

First start

Press Start on the Console tab. If the EULA has not been accepted yet, the panel asks you to accept it first. The server is up when the console prints a line containing For help, type. Your address is in the left rail under Server address. Connect to your server for the first time covers adding it in Minecraft.

The first start can stop on two client-only mods the panel did not leave out. When this guide was checked, the first Start stopped with Mod embeddiumextension requires embeddium. After that jar was gone, the next one stopped with Panorama has class loading errors. If yours stops the same way, open File Manager, go into the mods folder, delete embeddiumextension-1.16.5-0.0.2.jar and panorama-1.3.0.jar, and press Start again. With both deleted, the server reached the For help, type line.

Leave the world type alone

The server readme says not to change the world type in the server settings, and that the type the pack wants is quark:realistic. The pack's config/forge-common.toml sets defaultWorldType = "quark:realistic", so a new world gets it without any change from you. In the Config Editor, leave World type as it is and do not save over it, because its list offers Normal, Superflat, Large biomes, Amplified and Single biome, not the realistic type.

Common problems

• The server has no mods after the install. It was installed from the small server download instead of the client file. Install again from the Install your own pack card with the main file.
• A player cannot join. Check they run Crucial 2 1.5, then compare their mod list with the server's mods folder.
• The server lags or runs out of memory. Watch the RAM card on the Console tab and the TPS reading in the left rail. Why is my server lagging has more.
• The server stops at its first start. See the first start section: delete embeddiumextension-1.16.5-0.0.2.jar and panorama-1.3.0.jar from mods, then start again.
• The server crashes at boot. Find and read a crash report shows how to name the mod at fault.