Need to create systemd file and failing

Question

I'm trying to get a local Minecraft server going, and while there's a million and 2 tutorials out there, I'm trying to take it a step further than the scope of said tutorials and learn at the same time.

I found one tutorial that places a systemd .service file to start it on boot. Cool. Then, I found another that uses screen, which will help me immensely as I now have console access to it. And that's where I'm having trouble.

I created the forge-server.service file in the parent directory of the Forge server (allows mods, in case you didn't know), then I used "ln" to drop a link into /etc/systemd/system. And, it fails to load.

I get code=exited status=1 and a fail to start. I don't know what is going on. Half way down, I get no screen session found. Then, it just fails.

[Unit]
Description=Forge Server %i

[Service]
WorkingDirectory=/home/<USER>/minecraft/forge-server/%i
User=<USER>
Group=<USER>
Restart=always

ExecStart=/usr/bin/screen -DmS mc-%i /usr/bin/java -Xmx1536M -jar forge*.jar nogui

ExecStop=/usr/bin/screen -p 0 -S mc-%i -X eval 'stuff "say SERVER SHUTTING DOWN. Saving map..."15'
ExecStop=/usr/bin/screen -p 0 -S mc-%i -X eval 'stuff "save-all"15'
ExecStop=/usr/bin/screen -p 0 -S mc-%i -X eval 'stuff "stop"15'
ExecStop=/bin/sleep 2

[Install]
WantedBy=multi-user.target

If I don't specify the working directory as such, I get CHDIR200.

If I execute the Forge*.jar in my SSH/screen session, it works just fine. Can you please advise me where I went wrong and how to possibly fix this script?

EDIT: I figured it out. This is my new .service file;

#!/bin/sh -

[Unit]
Description=Forge Server

[Service]
WorkingDirectory=/home/<USER>/minecraft/forge-server/
User=<USER>
Group=<USER>
Restart=on-failure

ExecStart=/usr/bin/screen -DmS forge /usr/bin/java -Xmx1536M -jar forge-1.10.2-12.18.2.2099-universal.jar nogui

ExecStop=/usr/bin/screen -p 0 -S forge -X eval 'stuff "say SERVER SHUTTING DOWN. Saving map..."15'
ExecStop=/usr/bin/screen -p 0 -S forge -X eval 'stuff "save-all"15'
ExecStop=/usr/bin/screen -p 0 -S forge -X eval 'stuff "stop"15'
ExecStop=/bin/sleep 2

[Install]
WantedBy=multi-user.target

Answer 1

I figured it out. This is my new .service file;

#!/bin/sh -

[Unit]
Description=Forge Server

[Service]
WorkingDirectory=/home/<USER>/minecraft/forge-server/
User=<USER>
Group=<USER>
Restart=on-failure

ExecStart=/usr/bin/screen -DmS forge /usr/bin/java -Xmx1536M -jar forge-1.10.2-12.18.2.2099-universal.jar nogui

ExecStop=/usr/bin/screen -p 0 -S forge -X eval 'stuff "say SERVER SHUTTING DOWN. Saving map..."15'
ExecStop=/usr/bin/screen -p 0 -S forge -X eval 'stuff "save-all"15'
ExecStop=/usr/bin/screen -p 0 -S forge -X eval 'stuff "stop"15'
ExecStop=/bin/sleep 2

[Install]
WantedBy=multi-user.target

I had set the forge jar file as executable (chmod +x) and removed all the variables (%i from the initial script I copied). It now works and launches in a screen instance at boot.