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Using clanServices

Clan’s clanServices system is a composable way to define and deploy services across machines.

This guide shows how to instantiate a clanService, explains how service definitions are structured in your inventory, and how to pick or create services from modules exposed by flakes.

The term Multi-host-modules was introduced previously in the nixus repository and represents a similar concept.

Overview

Services are used in inventory.instances, and then they attach to roles and machines — meaning you decide which machines run which part of the service.

For example:

inventory.instances = {
  borgbackup = {
    roles.client.machines."laptop" = {};
    roles.client.machines."server1" = {};

    roles.server.machines."backup-box" = {};
  };
}

This says: “Run borgbackup as a client on my laptop and server1, and as a server on backup-box.”

Module source specification

Each instance includes a reference to a module specification — this is how Clan knows which service module to use and where it came from. Usually one would just use imports but we needd to make the module source configurable via Python API. By default it is not required to specify the module, in which case it defaults to the preprovided services of clan-core.

Override Example

Example of instantiating a borgbackup service using clan-core:

inventory.instances = {
    # Instance Name: Different name for this 'borgbackup' instance
    borgbackup = {
        # Since this is instances."borgbackup" the whole `module = { ... }` below is equivalent and optional.
        module =  {
            name = "borgbackup";  # <-- Name of the module (optional)
            input = "clan-core"; # <-- The flake input where the service is defined (optional)
        };
        # Participation of the machines is defined via roles
        # Right side needs to be an attribute set. Its purpose will become clear later
        roles.client.machines."machine-a" = {};
        roles.server.machines."backup-host" = {};
    };
}

If you used clan-core as an input attribute for your flake:

      # ↓ module.input = "clan-core"
inputs.clan-core.url = "git+https://git.clan.lol/clan/clan-core"

Simplified Example

If only one instance is needed for a service and the service is a clan core service, the module definition can be omitted.

# Simplified way of specifying a single instance
inventory.instances = {
    # instance name is `borgbackup` -> clan core module `borgbackup` will be loaded.
    borgbackup = {
        # Participation of the machines is defined via roles
        # Right side needs to be an attribute set. Its purpose will become clear later
        roles.client.machines."machine-a" = {};
        roles.server.machines."backup-host" = {};
    };
}

Configuration Example

Each role might expose configurable options

See clan's clanServices reference for available options

inventory.instances = {
    borgbackup-example = {
        module =  {
            name = "borgbackup";
            input = "clan-core";
        };
        roles.client.machines."machine-a" = {
            # 'client' -Settings of 'machine-a'
            settings = {
                backupFolders = [
                    /home
                    /var
                ];
            };
            # ---------------------------
        };
        roles.server.machines."backup-host" = {};
    };
}

Tags

Multiple members can be defined using tags as follows

inventory.instances = {
    borgbackup-example = {
        module =  {
            name = "borgbackup";
            input = "clan-core";
        };
        #
        # The 'all' -tag targets all machines
        roles.client.tags."all" = {};
        # ---------------------------
        roles.server.machines."backup-host" = {};
    };
}

Picking a clanService

You can use services exposed by Clan’s core module library, clan-core.

🔗 See: List of Available Services in clan-core

Defining Your Own Service

You can also author your own clanService modules.

🔗 Learn how to write your own service: Authoring a service

You might expose your service module from your flake — this makes it easy for other people to also use your module in their clan.

💡 Tips for Working with clanServices

  • You can add multiple inputs to your flake (clan-core, your-org-modules, etc.) to mix and match services.
  • Each service instance is isolated by its key in inventory.instances, allowing you to deploy multiple versions or roles of the same service type.
  • Roles can target different machines or be scoped dynamically.

What’s Next?