Chapter Objective

Describe the purpose of key directories in the Linux filesystem hierarchy, and navigate, create, copy, move, and locate files and directories from the command line.

The Filesystem Hierarchy Standard

Linux organizes all files into a single tree, starting at the root directory (/). Every file and directory on the system — regardless of which physical disk or partition it lives on — has a location somewhere under /. Red Hat Enterprise Linux follows the Filesystem Hierarchy Standard (FHS), a convention shared across most Linux distributions for what belongs where.

Key Top-Level Directories

Navigating Directories

Every process — including your shell — has a current working directory. Paths you type are interpreted relative to it, unless they start with /.

# Print the current working directory
pwd

# Change to an absolute path — always starts from root
cd /etc/ssh

# Change to a relative path — starts from where you are now
cd ../ssh

# Shortcuts
cd ~        # your home directory
cd          # also your home directory (no argument)
cd -        # the previous directory
cd ..       # the parent directory
cd .        # the current directory (rarely useful with cd itself)

Listing and Inspecting Files

# Basic listing of the current directory
ls

# Long format: permissions, owner, size, modification time
ls -l

# Include hidden files (those starting with a dot)
ls -a

# Combine common options
ls -la

# Human-readable file sizes (K, M, G instead of raw bytes)
ls -lh

# List a specific directory without changing into it
ls -l /etc/ssh

Identifying File Types

# Determine what kind of content a file actually contains
file /etc/passwd
file /usr/bin/bash
file /etc/ssh/ssh_host_ed25519_key

Creating, Copying, Moving, Removing

# Create a new empty directory
mkdir project

# Create nested directories in one step
mkdir -p project/src/lib

# Create an empty file, or update its timestamp if it exists
touch notes.txt

# Copy a file
cp notes.txt notes-backup.txt

# Copy a directory and its contents recursively
cp -r project/ project-backup/

# Move or rename a file (mv does both)
mv notes-backup.txt archive/notes-2026.txt

# Remove a file
rm notes.txt

# Remove a directory and everything inside it
rm -r project-backup/

# Prompt before each removal — a safer habit for destructive commands
rm -ri project-backup/

Hard Links and Symbolic Links

A link lets one or more names refer to the same underlying data. Linux supports two kinds.

# Create a hard link
ln original.txt hardlink.txt

# Create a symbolic link
ln -s /etc/ssh/sshd_config sshd_config_link

# Symlinks are visually distinguishable in a long listing (-> target)
ls -l sshd_config_link

Finding Files

# Find files by name under a starting directory
find /etc -name "*.conf"

# Case-insensitive name search
find /home -iname "*report*"

# Find only regular files, or only directories
find /var/log -type f
find /var/log -type d

# Find files modified in the last 1 day
find /etc -mtime -1

# Find files larger than 100 megabytes
find / -size +100M

Key Terms for Chapter 6

Filesystem Hierarchy Standard (FHS)

The convention defining the purpose of standard top-level Linux directories

root directory

The top of the filesystem tree, written as /

working directory

The directory a process (such as your shell) is currently "in"

absolute path

A path that starts from the root directory /

relative path

A path interpreted starting from the current working directory

inode

The data structure storing a file's metadata and location on disk, separate from its name

hard link

A directory entry pointing to the same inode as another name; cannot cross filesystems

symbolic link (symlink)

A special file that stores a path to another file or directory; can cross filesystems

find

Command that searches the live filesystem for files matching given criteria

Review Questions

1. Where does RHEL store system-wide configuration files, and where does it store variable data like logs?
2. What is the difference between cd .. and cd -?
3. You see a file named data.txt but suspect it isn't actually plain text. What command would confirm what it really is?
4. What option to mkdir lets you create a directory and any missing parent directories in one command?
5. Why is rm -r considered dangerous, and what option can make it safer to run interactively?
6. What happens to a symbolic link if the file it points to is deleted? What about a hard link in the same situation?
7. Write a find command that searches /var/log for regular files larger than 50 megabytes.