Templates

Templates let you create game servers without needing to configure all the technical details by yourself. Instead of manually configuring the Docker image, ports, environment variables, and commands, you select a template and COSY fills in everything for you.

How Templates Work

COSY fetches templates from the cosy-templates repository via an external Template Service. Templates are defined as YAML files, validated against a JSON schema, and synced periodically.

Each template specifies:

• Docker image name and tag
• Port mappings (TCP/UDP)
• Environment variables (with support for user-configurable variables)
• File mounts for persistent storage
• Resource limits (CPU and memory)
• Execution command (optional)

Available Templates

Templates are organized by game in the templates/ directory. The list below is fetched live from the template service:

Loading templates...

The collection is community-maintained — new games and variations are added through pull requests.

Using a Template

Templates are selected during the server creation process. For a detailed walkthrough, see Your First Game Server.

In short: create a new server, pick a game, select a template, fill in any template variables (e.g., memory allocation, player limits), and create the server. You can modify any template-provided setting after creation through the server's configuration page.

Template Variables

Templates can define variables — user-configurable inputs that get substituted into environment variables using {{placeholder}} syntax.

For example, the Minecraft Fabric template defines a version variable. When you fill in 1.21.2, the environment variable VERSION is set to 1.21.2 inside the container.

Variable types:

Each variable can also specify:

• regex — A regular expression to validate user input (string type only). For example, \d\.\d+\.\d+ ensures a valid version number like 1.1.6.
• default — A default value that is pre-filled when creating the server.
• example — An example value shown as a hint in the input field.
• options — A list of allowed values (required for the select type).

Contributing Templates

If you'd like to request a template for a game that isn't supported yet, you can open a template request issue. If you want to contribute one yourself, submit a pull request to the cosy-templates repository.

Templates must be placed at templates/{game-name}/{template-description}.yaml using lowercase letters and dashes.

Template Format

# yaml-language-server: $schema=../../schema/template.schema.json
name: Minecraft Fabric
description: Minecraft Fabric Server with default fabric installation
game_id: 38365
docker_image_name: itzg/minecraft-server
docker_image_tag: latest

variables:
  - name: Minecraft Version
    type: string
    regex: \d\.\d+\.\d+
    placeholder: version
    example: "1.21.2"
  - name: Memory Allocation (in Gigabyte)
    type: string
    placeholder: memory
    example: "4"
    default: "6"

environment_variables:
  VERSION: "{{version}}"
  EULA: "true"
  TYPE: "FABRIC"
  MODRINTH_PROJECTS: "fabric-api"
  MEMORY: "{{memory}}G"

port_mapping:
  "25565/tcp": 25565

file_mounts:
  - /data

resource_limit:
  memory: 6GiB
  cpu: 3

Required Fields

Optional Fields

All templates are validated against a JSON schema in CI before they can be merged.