In which mode does the system operate when set to runlevel 3?

When a system is set to runlevel 3, it operates in multi-user mode. This mode allows multiple users to access the system concurrently, supporting various non-graphical network services and applications. In this state, all necessary services for normal system operation are running, such as networking and remote login capabilities, which makes it suitable for servers and environments where a graphical interface is not required.

Runlevel 3 does not include a graphical user interface, which distinguishes it from graphical mode, typically associated with runlevel 5 in many Linux distributions. It also is different from single-user mode, which restricts access to a single user for maintenance purposes and runs a minimal set of services. Additionally, maintenance mode, often another term for single-user mode, does not provide the multi-user capabilities that runlevel 3 does. As a result, runlevel 3 is essential for enabling multi-user interactions without the overhead of a graphical environment.