Startup Issue with Minecraft - AMP not choosing correct start options

System Information

Field Value
Operating System Linux - Debian GNU/Linux 12 on x86_64
Product AMP ‘Decadeus’ v2.4.6.6 (Mainline)
Virtualization VMware
Application Minecraft
Module MinecraftModule
Running in Container No
Current State Installing

Problem Description


I’m trying to start a modded forge server with version 40.2.9. I can download and install the server but when I try to start it, AMP uses the forge installer jar instead of the new startup arguments used by the newer forge versions. After deleting the installer, AMP just re-downloads the installer or tries to start a non-existing minecraft_server.jar.

Reproduction Steps

  • Create new instance and select Forge → Stable → v40.2.9
  • Update the server and install correct forge version
  • Try to start the server with Forge v40.2.9 still selected in server options
  • AMP tries to use remaining installer.jar from forge instead of picking correct startup args
  • After deleting the installer.jar, AMP either tries to re-download forge oder output an error about a missing minecraft_server.jar

Make sure that the startup Jar in AMP is set to “Autoselect”.

It is set to [Autoselect] in the instance UI and not set at all in the corresponding MinecraftModule.kvp.

And just to clarify - the server type is set to “Forge” and the forge version is selected?

Yes, they are set in AMP; restarting the instance keeps the settings in place although it does not change the described behaviour.

I have started Forge-servers in the past with the exact same configuration for instance and server but it just doesn’t want to work here.

After hitting Start, what does AMP show in the support tab?

Last Executable /usr/lib/jvm/temurin-18-jdk-amd64/bin/java
Last Arguments -Xmx6144M -jar forge-1.18.2-40.2.9-installer.jar nogui
Last Process ID 273

weird - remove the jar file and see what it picks afterwards?

Last Executable /usr/lib/jvm/temurin-18-jdk-amd64/bin/java
Last Arguments -Xmx6144M -jar minecraft_server.jar nogui
Last Process ID 314

It tries to pick a minecraft_server.jar which does not exist in the instance dir. The server-config is still set to Forge v40.2.9.

Can you jiggle the handle on all those settings? Swapping the server type and version all back and forth.

Swip-swapping the Java version setting has helped this issue in the past, but that could’ve been random tbh.

Already tried to swap the forge version or select vanilla just to swap back to forge with the specified version. I tried to reproduce the error but it immediately worked on a new instance. After adjusting some settings however, the error occurred again; I will try to pinpoint the settings now.

Edit: The problem seems to be with the option Lock to official Server. The server was successfully installed and ran without any problems. After turning this setting on however and restarting the server, AMP wants to use the installer.jar again.

Last Executable /usr/lib/jvm/temurin-18-jdk-amd64/bin/java
Last Arguments -Xmx1024M -jar forge-1.18.2-40.2.9-installer.jar nogui

Steps to reproduce:

  1. Create new instance, download any forge server and install it
  2. Accept EULA and start the server and shut it down after a successful boot
  3. Turn on Lock to official Server
  4. Server fails to boot
  5. Turn off Lock to official Server
  6. Server boots successfully with correct start args
Last Executable /usr/lib/jvm/temurin-18-jdk-amd64/bin/java
Last Arguments -Xmx1024M @libraries/net/minecraftforge/forge/1.18.2-40.2.9/unix_args.txt

Well that is the expected behaviour under the circumstances xD

Ohhhh, well I should try and read the settings description properly next time :sweat_smile:
I thought it was to prevent unlicensed clients to join the server.

Thanks for your time anyway!

It literally says “Prevents modified servers from being used” xD

Yeah I only looked at the setting name rather than its description and thats my bad. Anyway, is there a use-case for this setting if it isn’t toggling online-mode in the

It’s for hosts that want to lock servers down and not let other server types be used. Although it’s mostly a hangover from MCMA2 and could actually be removed at this point.

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