# Agent > See first: [User docs | Agent](https://documentation.ubuntu.com/juju/3.6/reference/agent.md#agent) In Juju, an **agent** is any process that runs a dependency engine ([`dependency.NewEngine`](https://documentation.ubuntu.com/juju/3.6/contributor/reference/dependency-package.md#newengine)) to start and manage [workers](https://documentation.ubuntu.com/juju/3.6/contributor/reference/worker.md#worker-cont) for a particular domain entity in a particular deployment environment. ## List of agents While Juju agents can be counted based on the number of files in the codebase that invoke `dependency.NewEngine`, the type of process that they represent depends on the specific [`jujud`](https://github.com/juju/juju/blob/3.6/cmd/jujud/doc.go) / [`containeragent`](https://github.com/juju/juju/blob/3.6/cmd/containeragent)) agent-creating command that they invoke, and the workers that they bring up depend on the specific manifold declaration (files conventionally called `*manifolds.go` that invoke [`dependency.Manifolds`](https://documentation.ubuntu.com/juju/3.6/contributor/reference/dependency-package.md#manifolds)) that is used to configure the dependency engine. Thus, starting from the list of files that invoke a dependency engine, and factoring in these variations, one can distinguish the following agents: #### NOTE You can think of the list of agents based on invocations of `dependency.NewEngine` files as the ‘actual agents’ and of the list of agents arising from the various splits defined in those files as the ‘logical agents’. - [`cmd/jujud/agent/machine.go`](https://github.com/juju/juju/blob/3.6/cmd/jujud/agent/machine.go)
Uses [`jujud/main.go` > `NewMachineAgentCmd`](https://github.com/juju/juju/blob/3.6/cmd/jujud/main.go) with [cmd/jujud/agent/machine/manifolds.go](https://github.com/juju/juju/blob/3.6/cmd/jujud/agent/machine/manifolds.go) and [cmd/jujud/agent/model/manifolds.go](https://github.com/juju/juju/blob/3.6/cmd/jujud/agent/model/manifolds.go) to define an agent with multiple modes that will run different sets of workers depending on whether the target is - a machine (in a machine deployment; with subdistinctions based on whether it is a regular machine or rather a container running on top of a machine; whether the machine carries a controller, model, unit) or - a container (specifically, the controller container in a Kubernetes deployment, with subdistinctions for whether it has a model on it as well or not). - [`internal/worker/deployer/unit_agent.go`](https://github.com/juju/juju/blob/3.6/internal/worker/deployer/unit_agent.go)
Uses [`jujud/main.go` > `NewMachineAgentCmd`](https://github.com/juju/juju/blob/3.6/cmd/jujud/main.go) ( indirectly, through the `deployer` worker from the [`cmd/jujud/agent/machine.go`](https://github.com/juju/juju/blob/3.6/cmd/jujud/agent/machine.go) agent) and [`internal/worker/deployer/unit_manifolds.go`](https://github.com/juju/juju/blob/3.6/internal/worker/deployer/unit_manifolds.go) to define an agent that will run workers for units in a machine deployment. - [`cmd/jujud/agent/model.go`](https://github.com/juju/juju/blob/3.6/cmd/jujud/agent/model.go)
Uses [`jujud/main.go` > `NewModelCommand`](https://github.com/juju/juju/blob/3.6/cmd/jujud/main.go) and [`cmd/jujud/agent/modeloperator/manifolds.go`](https://github.com/juju/juju/blob/3.6/cmd/jujud/agent/modeloperator/manifolds.go) to define an agent that will run the modeloperator pod in a Kubernetes deployment. - [`cmd/containeragent/unit/agent.go`](https://github.com/juju/juju/blob/3.6/cmd/containeragent/unit/agent.go)
Uses [`containeragent/main_nix.go` > `containerAgentCommand`](https://github.com/juju/juju/blob/3.6/cmd/containeragent/main_nix.go) and [cmd/containeragent/unit/manifolds.go](https://github.com/juju/juju/blob/3.6/cmd/containeragent/unit/manifolds.go) to define an agent that will run workers for units in a Kubernetes deployment. - [`cmd/jujud/agent/caasoperator.go`](https://github.com/juju/juju/blob/3.6/cmd/jujud/agent/caasoperator.go) ( deprecated)
Uses [`jujud/main.go` > `NewCaasOperatorAgent`](https://github.com/juju/juju/blob/3.6/cmd/jujud/main.go) and [`cmd/jujud/agent/caasoperator/manifolds.go`](https://github.com/juju/juju/blob/3.6/cmd/jujud/agent/caasoperator/manifolds.go) to define an agent that will run workers for podspec charms (deprecated).