Processes & Signals

This page is about how Linux manages running programs — how they’re created, monitored, and controlled.
It’s a core topic that connects directly to scripting, scheduling, service management, and system recovery.

What is a Process?

A process is a running instance of a program.
Each process has a unique PID (Process ID) and runs in its own memory space.
Processes can spawn other processes, communicate with each other, and respond to signals.

Basic Commands

• ps aux
  Lists all running processes with details like PID, CPU usage, and command.

• top / htop
  Live monitoring of system resources and active processes.

• kill <PID>
  Sends a signal to a process — usually to terminate it.

• pmap <PID>
  Shows memory usage of a specific process.

Common Signals

Signal	Description
SIGTERM	Graceful termination request
SIGKILL	Forceful kill, cannot be caught
SIGINT	Interrupt from keyboard (Ctrl+C)
SIGSTOP	Pause the process
SIGCONT	Resume a stopped process

What’s Next

This page will grow to include:

• Process states and lifecycle
• Foreground vs background jobs
• Daemons and service management
• Signal handling in scripts
• Scheduling with cron and at

This is one of the leaves under my Linux branch.
It’s where I collect the tools and concepts that help me understand what’s running — and how to control it. |