Part 2 · Lesson 6 · Intermediate

The Process Tree

Every process has a parent. Meet PID 1.

In this interactive Linux lesson from Stencel Academy you don't just read — you type real commands like pstree, ps -ef and watch the machine respond on a live, animated map. It is part of the free How Linux Works course.

Key takeaway: Processes form a tree rooted at PID 1 — every process has a parent.

Before this lesson

Builds on: From Program to Process.

What you'll practise

pgrep bash — Find PIDs by name.
ps -o pid,ppid,comm — Pick exactly the columns you want.
pstree -p — Same tree, with PIDs attached.

Terms you'll learn

PID 1systemdparent (PPID)pstreeprocess tree

Check your understanding

What sits at the root of the process tree?

PID 1 (systemd) — ancestor of all
Your shell
The kernel itself

Open the interactive lesson →