What is the process ID number of the init process on a System V init based system?

The process ID (PID) of the init process on a System V init based system is always 1. The init process is the first process that gets started during the booting of the operating system and is responsible for starting other processes. It acts as the parent of all other processes in the system, which is why it has the PID of 1. This consistent assignment ensures functionalities like managing system run levels and handling process termination, making it a fundamental component of System V init systems.

The other options do not accurately represent the PID of the init process. A PID of -1 does not exist in standard UNIX-like systems, as PIDs are non-negative integers; 0 is typically reserved for the scheduler or the idle process, not init; and while the PID might vary for other processes across reboots, the init process maintains a PID of 1 consistently.