Which run level allows the system to operate without any network services?

The run level that allows the system to operate without any network services is run level 1. This level, often referred to as "single-user mode," is primarily used for administrative tasks. In run level 1, the system boots into a single-user mode where only the root user is allowed to log in and no network services are started. This mode is beneficial for tasks requiring maintenance, recovery, or troubleshooting without the interference of network services.

Run level 0 is used to halt the system, effectively shutting it down, while run levels 2 and 3 are multi-user modes that allow for various networking services. Run level 2 is often designed to allow multi-user access without networking services active (this can vary by distribution), but it is not a definitive "without network services" level like run level 1. Run level 3 is multi-user mode with network services enabled, making it unsuitable for scenarios where no network should be active.

Therefore, the characteristics of run level 1 make it the appropriate choice when discussing a mode of operation that excludes network services entirely.