Process Management

Introduction

In Linux, a process is a running instance of a program. Understanding how to view and manage processes is essential for system administration and troubleshooting.

Viewing Processes

ps - Process Status

$ ps                 # Show processes in current terminal
$ ps aux             # Show all processes (BSD style)
$ ps -ef             # Show all processes (System V style)
$ ps aux | grep nginx  # Filter for specific process

Common columns:

• PID - Process ID (unique identifier)
• USER - Process owner
• %CPU - CPU usage percentage
• %MEM - Memory usage percentage
• STAT - Process state
• COMMAND - Command that started the process

top / htop - Interactive Process Viewer

$ top                # Real-time process viewer
$ htop               # Enhanced version (if installed)

Press q to exit, k to kill a process, h for help.

pgrep - Find Process by Name

$ pgrep nginx        # Get PID of nginx process
$ pgrep -l nginx     # Include process name

Process States

State	Code	Description
Running	R	Currently executing or ready to run
Sleeping	S	Waiting for an event
Stopped	T	Stopped (e.g., Ctrl+Z)
Zombie	Z	Terminated but not cleaned up

Signals

Signals are used to communicate with processes:

$ kill PID           # Send SIGTERM (graceful shutdown)
$ kill -9 PID        # Send SIGKILL (force kill)
$ kill -STOP PID     # Pause process
$ kill -CONT PID     # Resume process
$ killall nginx      # Kill all processes by name

Background & Foreground

Running in Background

$ sleep 100 &        # Start in background
$ jobs               # List background jobs
$ fg %1              # Bring job 1 to foreground
$ bg %1              # Resume job 1 in background

Ctrl+Z and Ctrl+C

• Ctrl+C - Terminate foreground process (SIGINT)
• Ctrl+Z - Suspend foreground process (SIGTSTP)

Your Task

1. Start a long-running process in the background
2. Verify it’s running with ps
3. Check its job number with jobs

Run this command to start the background process:

sleep 300 &

Then verify it’s running.

Launch Your Sandbox

Copy the command below to start this exercise: