Runlevels
Runlevels are a concept in Unix-like operating systems that define different system states or modes, each specifying which services and processes are running. They are used to control the system's operational mode, such as single-user mode for maintenance or multi-user mode with networking. This allows administrators to manage system startup, shutdown, and transitions between different operational states.
Developers should learn about runlevels when working with system administration, server management, or embedded systems on Unix-like platforms like Linux, as they are crucial for controlling system behavior during boot, shutdown, and maintenance. For example, use runlevels to troubleshoot issues in single-user mode, configure services to start automatically in multi-user mode, or ensure critical processes run only in specific states. Understanding runlevels helps in writing scripts, managing daemons, and optimizing system performance.