runlevelin

Runlevelin is a theoretical descriptor used to characterize the instantaneous configuration of a complex automated or cyber-physical system. It captures which software modules are active, how they are interconnected, and the resource allocations at a given moment. The concept is distinct from the Unix term runlevel and is used mainly in modeling, simulation, and formal analysis of dynamic systems.

A Runlevelin is usually represented as a compact data object that includes an identifier, a timestamp, and a status map for components and services. Common components in the status map include modules, services, and resources, with binary indicators or categorical status values such as active, idle, or failed. A simple example might specify that the kernel and authentication services are active, the web service is active, the database is idle, and CPU and memory usage are given.

Transitions between runlevels are governed by control policies or external events. The Runlevelin framework emphasizes state invariants—certain critical components may remain fixed while others reconfigure—and transition rules that ensure safe changes. This makes runlevel transitions suitable for formal verification and model checking.

Applications include modeling and testing of deployment pipelines, disaster recovery simulations, and performance analysis in distributed systems. It provides a neutral abstraction to compare configurations and reason about system behavior under stress or during maintenance windows. Limitations include abstraction gaps and potential overspecification of real-time constraints.

Origin and usage: The term Runlevelin appears in theoretical discussions and niche literature dealing with state descriptors for complex systems. It is not part of standard terminology in mainstream operating-system literature, and references typically treat it as an illustrative construct rather than an established concept.