Setting Up A Modded Java Minecraft Server

[ThePotatoKing]

Preamble

Minecraft is a bit notorious for being difficult to mod, given there’s oodles of different modloaders and versions to work with, there’s edge cases galore.
If you’re new to the Minecraft modding scene and you’d like to know more about each modding platform and how they differ, check out this post here.

0. Create a new Minecraft Java Instance in AMP

Easy as that, press the Create Instance button, then select Minecraft Java Edition from the drop-down. Feel free to use an existing instance as well if you already sorta know what you’re doing (sometimes things are easier with a blank slate).

1. CurseForge

Just as a general note, do not try and upload the client manifest zip or the “server pack” from the CurseForge launcher, as that is seemingly busted.

1.1. Finding and Importing the Server Pack Zip into AMP

Thank @Greelan for this bit, I forgot you could do it this way.

Step 1: Go to the CurseForge page of your choice. For the purposes of this guide, we’ll be looking at ATM10 since it covers a few weird edge cases.

Step 2: Browse to the Files tab and click on the version of the pack you want to run

Step 3: Scroll down a little and click on the Additional Files section below the version info

Step 4: Click the ... next to the file and press Download File

Step 5: Cancel the download, then right-click and copy the try again link

Step 6: Manage the Minecraft instance and click on the File Manager tab on the left

Step 7: Right click an empty space in the File Manager and press Download file here

Step 8: Enter the URL into the field and press Ok

Step 9: Right click the file named download and rename it to server.zip

1.2. Extracting the Zip

Sounds easy doesn’t it? Sometimes it is, and other times things are extra complicated for seemingly no reason. so much fun

Step 1: Right click the server.zip and press Extract Here

Step 2: Assess the situation

Normally in the / directory you should now have a pile of new files named mods, config, libraries etc. And if you click on the mods folder you should see a bunch of .jar files (those are your mods).
If you see those files you can skip to 1.4. Cleanup.

If you only see one new folder (like in this example), continue on to Step 3

Step 3: Right click the new folder and press Create Archive

Counter intuitive, I know, but bear with me.

Step 4: Right click your new zip and press Extract Here

Things are in the right place now! You should see all of the folder’s files barfed into the / directory.

1.3. Double Check

Check that you now have some new config and mods, and some other folders in the server’s directory.

If not, review the steps for extracting the zip to make sure the files aren’t in a nested folder, otherwise the pack might have one of those stupid start scripts that downloads the mods.
Commonly those are labled as a startserver.sh/.bat or installserver.sh/.bat.

If that is the case:

1. Download the modded files to a folder on your PC
2. Run the installer in that folder (double click the .bat (BATCH) file if you’re on Windows)
3. Select all the files inside the folder
4. Zip the files
5. Upload the zip to AMP and run through the previous section again

1.4. Cleanup

You can now delete any .zip you used while setting up the server, and delete the extra ServerFiles folder if you have one of those as well.

Now you’re ready to move onto 3. Configuring the Server to finish setting up the server.

2. Feed The Beast

2.1. Installation

Currently there’s a slight bug in AMP, requiring you to delete all of the instance’s files before running the modpack installer.

When following 3. Configuring the Server you will need to change the Server Type setting to the required modloader. The server won’t start properly otherwise.

2.1.1. x86 Systems

Step 1: Delete the server.properties file and the plugins folder, then right click the Trash folder and empty it.

Step 2: Set the Server Type setting to Feed The Beast (New Source)

Found under Configuration -> Minecraft -> Server and Startup

Step 3: Select the modpack you want using the FTB Modpack setting

Step 4: Press Download/Update

Step 5: Continue onto 3. Configuring the Server to finish setting up the server

2.1.2. ARM Systems

If you’re running Linux and you’re familiar with the terminal, upload the ARM installer to AMP using AMP’s File Manager and run it as the amp Linux user.
First run sudo su -l amp, then you’ll find the file under /home/amp/.ampdata/instances/{TheInstnaceName}/Minecraft

Step 1: Download the server installer from the FTB site

Step 2: Run the installer on your PC in a new folder

Step 3: Select the files inside the folder and zip them

Step 4: Extract the .zip using AMP’s File Manager

*For a more in-depth rundown on working with the zip, see 1.2. Extracting the Zip

Step 5: Continue onto 3. Configuring the Server to finish setting up the server

3. Configuring the Server

In this section we’ll be going over how you can find important modloader and Java information across different files and enter that info into AMP’s web interface.

3.1. AMP’s Settings

The following settings are all in Configuration -> Minecraft
Here we go with some definitions:

• Arg -Xmx:
  → Goes under Java and Memory -> Memory Limit (MB) in terms of megabytes (1 GB → 1024 MB)
  Note: Allocating more than 16GB of RAM can have a negative performance impact on the CPU due to larger Garbage Collection (GC) spikes.

• Arg -Xms:
  → Goes under Java and Memory -> Memory pre-allocation (MB) in terms of megabytes (1 GB → 1024 MB)
  Note: You can leave this as 256 MB unless directed otherwise by the modpack creator or the author of the startup arguments you’re using.

• Any argument prefixed with -D or -XX::
  Java and Memory -> Additional java options separated by spaces
  Note: Do not add these under Server and Startup -> Additional server arguments

• Arg -jar jarname.jar:
  → Select the Jar under Server and Startup -> Server Jar
  Note: Forge 1.17.1-1.20.2 and NeoForge 1.20.1-present do not have conventional startup Jars. In such cases, select the Server Type (modloader) and version the modpack needs and leave the Server Jar as Autoselect.

3.2. Understanding Start Scripts

Some common filenames for server start scrips are run.sh, start.sh, and startserver.sh. You’ll also see these files with the .bat file extension (you may have all, some, or none of these files, but the core ideas still apply).

3.2.1. Breaking Down run.sh

Open the run.sh file in AMP’s file manager.

1. This file contains a list of Additional java options that you can copy into AMP’s settings
2. Here you’ll see the Forge/NeoForge version the modpack is using

Here’s another example using a different startup command

1. Java and Memory -> Memory Limit (MB) → 4096
2. Java and Memory -> Memory pre-allocation (MB) → 2048
3. Java and Memory -> Additional java options → -Dfile.encoding=UTF8 -Dfml.readTimeout=180
4. Server and Startup -> Server Jar → forge-1.20.4-49.2.0-shim.jar
5. 49.2.0 would be the Forge version the modpack is using

3.2.2. Breaking Down startserver.sh

Please note, some of these alternate startup scripts may differ, so this is a general rundown using the one from the CurseForge example.
Open the startserver.sh file in AMP’s file manager.

At the top of the script you’ll see a line with:
NEOFORGE_VERSION=21.1.143, FORGE_VERSION=xxxx or FABRIC_VERSION=xxxx
This will be the Forge/NeoForge version the modpack is using

1. This file contains a list of Additional java options that you can copy into AMP’s settings

3.2.3. GTNH

I don’t have a screenshot handy at the moment, but GTNH differs slightly from the other examples.

Enter the following into your settings:

1. Server and Startup -> Server Type → Forge
2. Server and Startup -> Forge Version → The Forge version the pack currently uses
3. Server and Startup -> Server Jar → lwjg13ify-forgePatches.jar
4. Java and Memory -> Java version → Java 17 (or Java 21 if specified)
5. Java and Memory -> Additional java options → -Dfml.readTimeout=180 @java9args.txt

3.3. Modloader Information

You should see the modpack’s modloader and version in your launcher, or after loading up the modpack you’ll see the version info in the bottom left of the Minecraft main menu.

All of these settings are under: Configuration -> Minecraft -> Server and Startup

• For Server Type you’ll want to select Fabric, Forge, or NeoForge depending on the information shown.

• Now you’ll want to select the correct version of the modloader in AMP’s settings.

• Press Download/Update

• If you’re using Forge/NeoForge set the Server Jar to Autoselect

3.4. Java Settings

All of these settings are under: Configuration -> Minecraft -> Java and Memory

Most often the modpack’s authors will have a recommended amount of RAM to use for the server. If not, anywhere from 6-12GB should do.
This setting is called Memory Limit (MB)

Some modpacks also have suggested Java arguments for you to use while running the server.
You can add these under Additional java options
Make sure to exclude Xmx, Xms, jar, and nogui since AMP’s settings already handle these.

Some versions of Minecraft require different Java runtimes in order to start up and run correctly, so here’s a quick rundown (see a more in depth explanation below).
This setting is called Java Version

• Minecraft 1.7.10-1.15.2 use Java 8
• Minecraft 1.16.5 use either Java 8 or Java 11 depending on the mods you’re running
• Minecraft 1.17.1-1.20.4 use Java 17
• Minecraft 1.20.5-1.21.5 use Java 21

4. Additional Java Information

Minecraft Version	Server Type	Java Version	Class file version	Extra Notes
<= 1.4.7	any	Java 7	Class file version 51	Later versions work, mileage may vary
1.6.4	any	Java 7, 8	Class file version 52	Later versions work, mileage may vary
1.7 - 1.15.2	any	Java 8	Class file version 52	Later versions work, mileage may vary
1.16 - 1.16.5	any	Java 8, 11	Class file version 52 or 55	Later versions work, mileage may vary
1.16.x	Forge	Java 8, 11	Class file version 52 or 55	Depends on the mods you’re running
1.16.5	Paper	Java 16	Class file version 60	Can be disabled via a startup arg
1.17 - 1.17.1	any	Java 16, 17	Class file version 60 or 61	Later versions work, mileage may vary
1.18 - 1.20.4	any	Java 17	Class file version 61	Later versions work, mileage may vary
1.20.5 - 1.21.11	any	Java 21	Class file version 65	Later versions work, mileage may vary
26.1	any	Java 25	Class file version 69	Later versions work, mileage may vary

A table comparing Java runtime versions to class versions: Java version history - Wikipedia

See this post here regarding installing more Java runtimes: AMP Dependencies - Java
Please Note:
a. You’ll need to stop/start the MC instance via the main panel for the Java versions to refresh.
b. You may need to reboot if stopping/starting the instance doesn’t work

On Linux:
Run getamp installJava as root to download Java 8, 11, 17, 21, and 25

On Windows make sure:
a. You select the default install location
b. You add Java to the PATH variable

[Phillip_Souza]

Awesome tutorial man! We needed a Knowledge Base for setting up modded mc servers. Thank you so much for your time! Great Job!

[AlsBur_Soup]

If I have a mod pack that isn’t a original curseforge modpack but my mod pack thart i have what do i do?

[ThePotatoKing]

It’s pretty much the same idea, you just upload a zip of your mod files instead of grabbing a server pack zip.

[Dark_Rays_Of_Sunshin]

I’ve tried doing this with my own custom pack and it doesn’t work.

[FELIX_BRUNELLE]

ngl this is what the community needed, you basically covered what i was previously struggling with which is goated.

[ThePotatoKing]

Doesn’t work with custom packs, you’d need to upload the mods the usual way

[prope8]

Thank you for the walkthrough.

[Donavyn_Olson]

Everytime I try I just get a overrides folder and nothing exports.

[lancalot_007]

Did you ever find the solution?

[lancalot_007]

I found the solution. I was trying to run the new direwolf 20 on minecraft 1.21.1. You need to install the mods with a bat file that is in one of the files.