FTB Server starts and immediatle stops again with WebUI

I installed the mineos FreeNas plugin the other day and managed to have a running vanilla Server fairly quickly, but know we wanted to upgrade to modded Minecraft.
That’s why I created a new Server downloaded the profile for FTB Builders Paradise, copied the profile to live server files and ran the FTBInstall.sh.

First of all I’m not really sure wich jar to select in the java settings since there is the FTBServer and the minecraft_server jar.
No matter which one I choose, after clicking the start button, the UI says “UP” for a moment and then down again. It stays UP for longer when choosing the FTBServer jar and the memory footprint goes to around 2,5G.

The log in the UI has nothing new in it after pressing the button.
The mineos.log only has those lines in it:

{"level":"info","message":"[BuildersP] issued command : \"modify_sc\"","timestamp":"2019-09-11T20:20:02.978Z"}
{"level":"info","message":"[BuildersP] received request \"modify_sc\"","timestamp":"2019-09-11T20:20:02.978Z"}

Since I have no idea of java, minecraft servers in general, linux, mineos or anything related basically I have no idea what’s the cause but I already researched a bit on my own and I managed to start the Server via the Shell in FreeNas by running

sh ./ServerStart.sh

The problem with that method is that the server is down again as soon as I close the Shell.

The Eula is accepted although I needed to change the eula.txt via command line aswell and didn’t manage to do it via the WebUI.
Java is on version 8 as far as I can tell.
And I created a new User for MineOs since it wasn’t working with the mcserver User as well and I wasn’t sure if that is the root User in my case which I souldn’t be using as I managed to find out while researching.

If there is anything else you need I can probably tell you what you need! Thanks for helping.

Okay managed to figure it out. Or at least have a running server.

What I did is create a new server with forge. In this case I needed 12.2 latest. recommended didn’t work. Opened the jar and let it create the universal jar. Move those into your server folder and set it as the runnable jar. The server is now able to start.
Stopped again, I basically just copied over the important folders from my other server and started again. Still had some problems to fix: I had no rights for the worlds folder so the server created a new world with the old seed. Also I discovered that the recommended forge version didn’t work with Builders Paradise but I already mentioned it.

Anyway now it’s working as intended!