The present document describes systems and methods that authorize client resources such as computers, servers, computing appliances, and virtual machines to access online services provided by an online service provider. To authorize a client resource, a client submits a registration request on behalf of the client resource to an authorization service provided by the service provider. The authorization service returns an activation code to the client. The activation code may expire after an amount of time, or upon first use. The client provides the activation code to an agent running on the client resource. The agent establishes communication with the authorization service, and upon providing the activation code to the authorization service, receives an authorization token that can be used by the client resource to access online services in accordance with security roles or permissions specified with the registration request.