systemd service fails to start when I add mods

[wyattkoch]

My vanilla server (Los Dos Chismosos) works perfectly. My modded server (Cobblemon) doesn't, and I don't see why. I try to get this running, and I have followed other people's examples, but it's just not working for me and I can't seem to find anyone who has the same problem.

I know that the problem is the modpack as when I comment it out, it works fine, and I have tried with several mods/modpacks and have gotten nothing. The closest I have gotten was getting it to run with the fabric API (which is included in the modpack). Any help would be appreciated, and thank you for your time.

Link to modpack:
https://www.curseforge.com/minecraft/modpacks/cobbleverse-cobblemon

Permissions in /svr/minecraft:

[/etc/nixos]$ sudo ls -la /srv/minecraft
total 20
drwxrwx--- 5 minecraft minecraft 4096 Jun  7 08:25 . (/srv/minecraft)
drwxr-xr-x 3 root      root      4096 Jun  6 20:55 .. (/srv)
drwxrwx--- 3 minecraft minecraft 4096 Jun  7 08:25 .cache
drwxrwx--- 8 minecraft minecraft 4096 Jun  9 11:18 Cobblemon-Alpacas
drwxrwx--- 6 minecraft minecraft 4096 Jun  9 11:21 Los-Dos-Chismosos

systemd status:

[~]$ sudo systemctl status minecraft-server-Cobblemon-Alpacas.service
[sudo] password for wjkstra:
× minecraft-server-Cobblemon-Alpacas.service - Minecraft Server Cobblemon-Alpacas
     Loaded: loaded (/etc/systemd/system/minecraft-server-Cobblemon-Alpacas.service; enabled; preset: ignored)
     Active: failed (Result: start-limit-hit) since Mon 2025-06-09 12:13:27 PDT; 19min ago
   Duration: 566ms
 Invocation: 63b907ddb9414226bfe797e56deb93f2
    Process: 65933 ExecStartPre=/nix/store/whda881cwkkxkrgxpms7gn079vsr6819-minecraft-server-Cobblemon-Alpacas-start-pre/bin/minecraft-server-Cobblemon-Alpacas-start-pre (code=exited, status=0/SUCCESS)
    Process: 65948 ExecStart=/nix/store/wi8h4ikk98zcd1anyzh1lqnzhlgq4w96-minecraft-server-Cobblemon-Alpacas-start/bin/minecraft-server-Cobblemon-Alpacas-start (code=exited, status=0/SUCCESS)
    Process: 65963 ExecStartPost=/nix/store/kpsl9yq9mvbskrd6l7r0sp3xj9bi0k4z-minecraft-server-Cobblemon-Alpacas-start-post/bin/minecraft-server-Cobblemon-Alpacas-start-post (code=exited, status=0/SUCCESS)
    Process: 66059 ExecStop=/nix/store/404nanly2cwqfq3cw4wvrb5p3nv7j81i-minecraft-server-Cobblemon-Alpacas-stop/bin/minecraft-server-Cobblemon-Alpacas-stop $MAINPID (code=exited, status=0/SUCCESS)
    Process: 66063 ExecStopPost=/nix/store/akb6zbkvsq9dhs1zhrcky4rjqd5h2wch-minecraft-server-Cobblemon-Alpacas-stop-post/bin/minecraft-server-Cobblemon-Alpacas-stop-post (code=exited, status=0/SUCCESS)
   Main PID: 65956 (code=exited, status=0/SUCCESS)

Jun 09 12:13:27 Hal systemd[1]: minecraft-server-Cobblemon-Alpacas.service: Scheduled restart job, restart counter is at 5.
Jun 09 12:13:27 Hal systemd[1]: minecraft-server-Cobblemon-Alpacas.service: Start request repeated too quickly.
Jun 09 12:13:27 Hal systemd[1]: minecraft-server-Cobblemon-Alpacas.service: Failed with result 'start-limit-hit'.
Jun 09 12:13:27 Hal systemd[1]: Failed to start Minecraft Server Cobblemon-Alpacas.
[~]$

minecraft.nix

 pkgs, lib, inputs, ... }:

{
  imports = [ inputs.nix-minecraft.nixosModules.minecraft-servers ];
  nixpkgs.overlays = [ inputs.nix-minecraft.overlay ];

  services.minecraft-servers = {
    enable = true;
    eula = true;
    openFirewall = true;

    servers = {
      Los-Dos-Chismosos = {
        enable = true;
        package = pkgs.vanillaServers.vanilla-1_21_5;
        autoStart = true;
        jvmOpts = "-Xms1G -Xmx8G";

        serverProperties = {
          gamemode = "survival";
          motd = "Los Dos Chismosos";
          difficulty = "normal";
          server-port = 11315;
        };
      };

      Cobblemon-Alpacas = {
        enable = true;
        package = pkgs.fabricServers.fabric-1_21_1; #.override { loaderVersion = "0.16.14"; };
        autoStart = true;
        jvmOpts = "-Xms1G -Xmx8G";

        serverProperties = ({
          gamemode = "survival";
          server-port = 25118;
          motd = "Alpacas Cobblemon";
          difficulty = "hard";
          resource-pack = "https://modrinth.com/resourcepack/better-leaves";
        });

        #whitelist = {
        #
        #};

        # mods
        symlinks =
        let
          modpack = pkgs.fetchzip {
            url = "https://mediafilez.forgecdn.net/files/6564/693/COBBLEVERSE-1.3-CF.zip";
            hash = "sha256-b2ufer3vnnW/4+ew6XFgl0Ln4RC0CM+q1B27WQAnU8A=";
            stripRoot = false;
          };
        in {
          "mods" = "${modpack}/mods";
        };
      };
     };
  };
}

Edit:
I should also add that this same behavious occurs whether I fetch the zip or download and extract the zip, then correct the "mods" variable to the unzipped modpack's mods directory.

[Infinidoge]

Please check the Minecraft server logs, as the systemd service will fail to start if the Minecraft server itself crashes on start