Install GregTech: New Horizons Manually

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Install GregTech: New Horizons Manually

This guide covers how to manually install GregTech: New Horizons (GTNH) on your UltraServers-hosted Minecraft server. This is the officially recommended installation method using the Java 17-25 server pack.

Warning: This process requires deleting all existing server files. Back up your world and any important data before continuing.

Prerequisites

Before starting, make sure you have:

A server instance on UltraServers with access to the panel.
Access to the Files and Startup tabs in your server panel.
The server is STOPPED.

Download the Server Pack URL

Go to the official GTNH downloads page: gtnewhorizons.com/downloads
Scroll to the Server ZIPs section.
Right-click 1 "Latest for Java 17-25" and select 2 Copy link address.

Clear Server Files

In your UltraServers panel, go to the 1 Files tab.
Select 2 all existing files and 3 delete them and 4 move to trash. The directory must be completely empty before proceeding.

Warning: Deleting files is permanent. Ensure you have backed up your world data before this step.

Download the Pack via URL

In the Files tab, click the 1 Download from URL button.
2 Paste the GTNH server ZIP URL you copied earlier into the input field.
3 Confirm the download. The file will be fetched directly into your server's file system.

Note: The download may take a few minutes. The pack is approximately 350 MB.

Unarchive the ZIP File

Once the download completes, you will see a .zip file in your files list.
1 Right-click the .zip file and select 2 Unarchive.
Wait for the extraction to complete. All server files will be placed in the root directory.

After extraction, your files will include folders like mods/ and config/, as well as several .jar files — including the important one ending in -forgePatches.jar.

Set the Server JAR File

By default, the panel points to server.jar. GTNH requires a different JAR to start correctly.

In the Files tab, find the file whose name ends with 1 forgePatches.jar (e.g. forge-1.7.10-10.13.4.1614-1.7.10-forgePatches.jar).

Copy its full filename.
Navigate to the 2 Startup tab.
Find the Server JAR File field, clear the current value (server.jar), and 3 paste the full name of the forgePatches.jar file.
Saves automatically.

Set the Docker Image to Java 25

Still in the Startup tab, find the Docker Image selector.
Change it to 1 Java 25.
Saves automatically.

Add the Required Startup Flag

GTNH requires a custom JVM class loader flag to boot correctly. Without it, the server will crash on startup.

In the Startup tab, locate the Startup Command or JVM Flags field.
1 Add a space at the end of the existing flags, then append the following:

-Djava.system.class.loader=com.gtnewhorizons.retrofuturabootstrap.RfbSystemClassLoader

Save the startup command.

Warning: Make sure there is a single space between the last existing flag and the new one. A missing space will break the startup command.

Start the Server

Navigate to the Console tab.
Click Start.
The first boot will take several minutes as Forge patches libraries — this is is expected suring the boot process.
Once you see Done! For help, type "help" in the console, your server is online.

Note: The first startup can take 5–10 minutes. Do not restart the server during this time.

If you require further assistance, you can open a support ticket here.

Feedback and suggestions can be submitted here or further discussed on our Discord server.

Install GregTech: New Horizons Manually
Prerequisites
Download the Server Pack URL
Clear Server Files
Download the Pack via URL
Unarchive the ZIP File
Set the Server JAR File
Set the Docker Image to Java 25
Add the Required Startup Flag
Start the Server