Process State

Process Tree

init (1) Process (Root Process)

• The first system process, ancestor of all others, responsible for initializing and managing system processes.
• Directly spawns system services processes:
  • syslogd (2781): Manages system logs.
  • cupsd (3043): Handles printing services.
  • smbd (2978): Provides Samba service for file sharing.
  • sshd (20484): Manages SSH connections, spawning sshd (678) for active sessions. SSH connections create child sshd processes, leading to shell sessions.

bash (1835) Process

• Started by sshd (678), indicating a user login via SSH.
• Spawns multiple subprocesses as user activities (editing, browsing, monitoring) generate child processes under bash:
  • vi (1892): User opened the vi editor.
  • firefox (1903): User launched the Firefox browser.
  • pstree (2001): User inspected the process tree.

Process Termination

Voluntary Termination

• The process completes its task and exits normally: exit(0);

Forced Termination

• By another process using a signal:

  kill(pid, SIGKILL); // Forcefully terminate process

• By the OS due to illegal operations (e.g., segmentation fault).

• By itself using abort() (forces the calling process, parent or child, to terminate abnormally):

  abort(); // Immediately terminates the process that calls it

Zombie Process Handling

• A zombie process is a terminated child that hasn’t been reaped by wait().

• To clean up zombies, the parent should call:

  wait(NULL); // Collects child's exit status