FTB Modpack always uses provided java Version from FTB

[Sijo54]

Describe the problem

When starting a Server with FTB Mod pack, it will download the FTB installer and install the mod pack. After installation, it will run the mod pack using the provided run.sh.
With the current arguments to the FTB installer ${ftbInstaller} -pack "${FTB_MODPACK_ID}" -version "${FTB_MODPACK_VERSION_ID}" -auto -force (see line 96 in scripts/start-deployFTBA) the installer will automatically install a java file alongside the mod pack files, this java file is referenced in the run.sh file. This results in starting the Minecraft server with this provided Java version and not the Version configured with the server tag.

I would expect the server to always use the minecraft version provided from the container.

A Solution could be, to change the options of the installer. Adding the option -no-java would result in not installing a java alongside the mod pack and using the java configured in the container.
As an alternative, one could add an Environment Variable to configure this behavior.

Container definition

services:
mc-stoneblock-4:
image: ghcr.io/itzg/minecraft-server:java25
container_name: mc-stoneblock-4
tty: true
stdin_open: true
environment:
TZ: "Europe/Berlin"
EULA: "TRUE"
INIT_MEMORY: "16G"
MAX_MEMORY: "16G"
TYPE: "FTBA"
FTB_MODPACK_ID: "130"
FTB_MODPACK_VERSION_ID: "100171"
MODS: |
https://mediafilez.forgecdn.net/files/5657/655/Prometheus-Exporter-1.21.1-neoforge-1.2.1.jar
https://mediafilez.forgecdn.net/files/7361/105/player_trading-1.21.1-0.3.0.jar
https://mediafilez.forgecdn.net/files/6784/443/createstockbridge-1.21.1-0.1.6.jar
ports:
- "25565:25565"
volumes:
- ./data/minecraft/stoneblock-4:/data
restart: unless-stopped
stop_grace_period: 2m

Container logs

Paste logs here

[itzg]

Thanks for reporting this. I absolutely don't want FTB to be installing their own JVM.

Thanks for identifying -no-java since that is definitely what seems to be needed there.

It would be great if you could submit a PR for that.

[itzg]

Somebody else just ran into this. Thanks to your initial research I was able to quickly address it in #3867