UNIX Computing Security/System processes

System processes of UNIX consist of those processes that are not user services or user processes. One of the most known is init.

Init
The parent of all processes. init will take ownership of orphaned processes. Process ID is almost always 1.

Viewing processes
For example, a user may list the status of his or her processes using the  command, thus:

$ ps -f UID        PID  PPID  C     STIME TTY      TIME CMD john_doe 15265 15254  0  11:18:13 pts/5   00:00 -sh john_doe 11407 15265  1  13:52:09 pts/5   00:00 ps -f

The user with the account name  is the owner of the two processes with process identifiers 15265 and 11407. That user can send signals to those two processes using the  command. However the system can prevent that user from using the  command on processes he does not own.