# Navigating the Filesystem

## Everything is one tree, starting at `/`

Linux has exactly one filesystem tree, rooted at `/` (pronounced "root," unrelated to your
username). Every file and directory, no matter what physical disk it's actually on, appears
somewhere under this one tree — there's no separate "C:\" and "D:\" the way Windows shows
multiple drives.

## Absolute vs. relative paths

An **absolute path** starts with `/` and always means the same location no matter where you
currently are: `/home/student/notes.txt`. A **relative path** is interpreted relative to your
CURRENT directory: `notes.txt` means something different depending on where you're standing
when you type it. `.` means "this directory," `..` means "one directory up" — `cd ..` moves up
one level, `cd ../..` moves up two.

## Key commands

- `pwd` — print your current directory (where am I?)
- `ls` — list what's in a directory (`ls -la` shows hidden files and details)
- `cd <path>` — change directory (absolute or relative)

## Hidden files

A file or directory starting with `.` (like `.bashrc` or `.config`) is "hidden" — `ls` skips it
by default, `ls -a` shows it. This isn't a security feature, just a convention to keep
configuration/metadata files out of the way of normal directory listings.

## The important top-level directories (conceptually, not memorized)

You don't need to memorize the entire Filesystem Hierarchy Standard, but recognizing these by
purpose will save you real confusion later:

- **`/etc`** — system-wide configuration files (nginx's config lives at `/etc/nginx/nginx.conf`)
- **`/var`** — variable data that changes while the system runs: logs (`/var/log`), among others
- **`/home`** — personal directories for regular users
- **`/tmp`** — temporary files, safe to assume anything here can disappear on reboot
- **`/usr`** — most installed programs and their supporting files live somewhere under here
- **`/proc`** — not real files on disk at all — a live, kernel-generated view into running
  processes and system state (you'll use this again in Module 5)

## Instructor Notes

**Lesson goal:** Give students a working mental model of "one tree, absolute vs. relative
paths" plus just enough top-level-directory recognition to not be lost later — not FHS
memorization.

**Approximate timing:** 15 minutes read; 10 minutes live.

**Common misconception to watch for:** students coming from Windows sometimes expect separate
drives/roots — emphasize the single unified tree explicitly.

**Demo idea:** `cd /` then `ls`, narrating what each top-level directory is for as you see it,
rather than listing them in the abstract.