Oedipal Questions - Parents And Families Every process has a parent process. If the parent process exits, the child process automatically becomes the child of process 1 ('init'). A process and all its descendants form a 'process group'. One may send signals to a full process group using the 'kill' command with a negative PID. for example, 'kill -HUP -1212' will send the 'HUP' signal to all processes that belong to process group '1212'. The process group number is identical to the PID of the process that started the group. In order to belong to a new process group, a process issues the 'setsid' system call, which turns it into a leader of a new process group, or by using the 'setpgid' system call, which makes it join a given process group.