Explanation
The process ID number of the init process on a SysV init based system is 1. The init process is the first process that runs on the system, and it is responsible for initializing the user-space environment and spawning all other processes. The init process is always the first process that runs on the system, and it has the process ID (PID) of 1. The PID is a unique identifier for each process on the system, and it is assigned by the kernel.
The PID of the init process is always 1, regardless of the reboot or the run level. You can verify the PID of the init process by using the ps command, which shows information about the processes on the system. For example, to show the PID, the user, the command, and the arguments of the init process, use the following command:
ps -p 1 -o pid,user,cmd
The output of the command will show something like:
PID USER CMD 1 root /sbin/init
This shows that the init process has the PID of 1, the user of root, and the command of /sbin/init.
References:
* [SysVinit - ArchWiki]
* [Process Management in Linux - GeeksforGeeks]
* [ps(1) - Linux manual page]