without knowing what guide you are referring to its hard to tell what needs to be changed.
Also, it depends on what pack you want to play (or to be more precise, which version of minecraft said modpack uses)
Assuming for minecraft 1.12 you need to have java 8. Java 9 apparently doesn't work.
To check which version of java you have you can run the command
For me that prints out
Code:
openjdk version "1.8.0_151"
OpenJDK Runtime Environment (build 1.8.0_151-8u151-b12-1~deb9u1-b12)
OpenJDK 64-Bit Server VM (build 25.151-b12, mixed mode)
It shouldn't matter if you use the openjdk version or oracles version. But openJDK is probably easier to install as it can be done using apt-get.
The server also should have openssh-server and screen installed.
openssh-server is so you can connect to the server using ssh. If you don't plan on remote controlling the server, you can get away with not installing it.
screen is used so you can keep processes running after disconnecting from the server. Useful as else you would need to keep your ssh session running or the minecraft server would shutdown.
Install both using
Code:
sudo apt-get install screen openssh-server
after this is done, you can create a screen. I recommend to look through the manual for that command as it can do quite a bit of stuff.
Code:
man screen #shows the manual
screen -S "minecraftServer" #creates a new screen session called "minecraftServer". If you don't know what that means, run the above command and read :)
Now, its just as easy as getting the modpack on the server and running the correct .sh files (assuming they are provided with the modpack).
NOTE: Though I am successfully running a minecraft server on debian right now, the commands I posted come straight of my own memory and thus may be wrong(that is why I didn't go into detail on how to install java). Additionally, blindly running commands a stranger posted is a bad idea and can/will cause damage. Make sure you understand them before doing anything.
NOTE 2: the gui that comes with the minecraft server can/will cause performance issues. If your server has a gui you can disable the minecraft-server's gui using the flag "nogui"