PROCESSES (Linux)

🧠 PROCESSES (Linux) – MINI STUDY GUIDE

🔹 1. What is a Process?

Think of a process as a program that is currently running.

👉 Example:

  • Opening Chrome = isang process

  • Playing music = another process

đź’ˇ Key Characteristics

  • Can be started from:

    • GUI (click-click lang)

    • Command line (terminal)

  • Can create another process (parang parent-child relationship)

  • Important: A process can ONLY be created by another process

🧠 In short:

“Processes are like living programs—they can create, run, and manage other programs.”

🔹 2. Commands for Viewing & Controlling Processes

These are your main tools sa terminal:

Command

Purpose

ps

Shows snapshot of processes

top

Real-time process viewer

jobs

Lists active jobs

bg

Sends job to background

fg

Brings job to foreground

đź’ˇ Example:

  • ps = parang screenshot

  • top = parang livestream

🔹 3. Viewing Processes (ps Command)

🧾 What ps Shows

It gives you a list of running processes with details like:

  • User

  • CPU usage

  • Memory usage

âš™ Process States

State

Meaning

R

Running

S

Sleeping (waiting)

D

Waiting for I/O (e.g., disk)

T

Stopped

Z

Zombie (terminated but not cleaned)

đź“Ś According to page 1 table: Zombie processes are already dead but not yet removed by parent process

đź’ˇ Real-life analogy:

  • R = working student

  • S = naka-idle, waiting

  • Z = ghost đź‘» (exists but useless)

🔤 Extra Process Flags

Symbol

Meaning

<

High priority

N

Low priority

L

Locked in memory

s

Session leader

l

Multi-threaded

+

Foreground

🧠 Quick Summary Trick:

👉 “RSDTZ” = Run, Sleep, Disk, Stop, Zombie

🔹 4. Understanding ps aux Output

When you run ps aux, you’ll see:

Field

Meaning

USER

Owner

%CPU

CPU usage

%MEM

Memory usage

VSZ

Virtual memory

RSS

Actual RAM used

START

Start time

đź“Ś From page 2:

  • RSS = real memory usage

  • VSZ = virtual memory

đź’ˇ In short:

VSZ = “potential memory”
RSS = “actual ginagamit”

🔹 5. The top Command (Real-Time Monitoring)

Ito na yung boss-level monitoring tool 🔥

đź“Š System Summary (Top Section)

From the table on page 2:

  • Time – current system time

  • Uptime – how long system is running

  • Users – number of logged-in users

  • Load Average – how busy the CPU is

đź’ˇ Load average = pila ng processes sa CPU

🧠 CPU Breakdown

Field

Meaning

us

User processes

sy

System processes

ni

Low priority processes

id

Idle

wa

Waiting for I/O

hi

Hardware interrupts

si

Software interrupts

st

Time stolen (VM)

đź“Ś Important concept: Niceness

  • Higher niceness = lower priority

  • Lower niceness = higher priority

đź’ˇ Real-life:

“Nice ka → papasingit ka sa iba → less priority ka”

đź’ľ Memory Info

Field

Meaning

KiB Mem

RAM usage

KiB Swap

Virtual memory

🔹 6. Columns in top

From page 3:

Column

Meaning

PID

Process ID

USER

Owner

PR

Priority (-20 to 19)

NI

Niceness

VIRT

Virtual memory

RES

Real memory

SHR

Shared memory

S

Status

%CPU

CPU usage

%MEM

Memory usage

TIME+

CPU time used

COMMAND

Process name

đź’ˇ Important:

  • PR = priority level

  • NI = how “nice” the process is

🔹 7. Controlling Processes

🛑 Stop a Process

  • Ctrl + C

🔄 Background & Foreground

Action

Command

Send to background

bg

Bring to foreground

fg

Show jobs

jobs

đź’ˇ Example flow:

  1. Run program

  2. Stop it

  3. bg → runs in background

  4. fg → bring back

🧠 Real-life Analogy:

  • Foreground = ginagawa mo ngayon

  • Background = naka-open pero di focus

🧠 FINAL RECAP (Memory Hacks)

🔥 1. Commands

👉 “PJT-BF”

  • PS

  • Jobs

  • Top

  • BG

  • FG

🔥 2. Process States

👉 “RSDTZ”

  • Run

  • Sleep

  • Disk

  • Stop

  • Zombie đź‘»

🔥 3. Memory Types

👉 “Virtual vs Real”

  • VSZ = virtual (possible)

  • RSS/RES = real (actual)

🔥 4. Priority Trick

👉 “Nice ka = low priority”

🧠 FINAL TL;DR

Processes = running programs
ps = snapshot, top = real-time
States = RSDTZ
Priority controlled by niceness
Foreground vs Background = focus vs multitasking