Filesystem and Basic Commands

Introduction

Linux organizes everything as files under a single tree starting at /. Paths are case-sensitive and use forward slashes. This chapter maps important directories, then practices the commands you use every day: ls, cd, cp, mv, rm, and simple search.

Prerequisites

Linux learning environment
Access to a bash terminal (local or SSH)

Directory Layout (FHS Overview)

Path	Typical contents
`/`	Root of the whole tree
`/home/username`	Your personal files (`~`)
`/etc`	System and app configuration
`/var`	Logs, databases, variable data
`/tmp`	Temporary files (may clear on reboot)
`/usr`	Installed programs and libraries
`/opt`	Optional third-party bundles
`/root`	Home directory for root user

There is no C: drive—one filesystem tree, possibly spanning multiple disks mounted at folders like /data.

Paths: Absolute, Relative, and Special Names

Form	Meaning
`/etc/ssh/sshd_config`	Absolute from root
`docs/readme.md`	Relative to current directory
`~` or `$HOME`	Your home directory
`.`	Current directory
`..`	Parent directory

bash

# Print current directory
pwd
 
# Go to home
cd ~
cd
 
# Go to parent
cd ..
 
# Go to absolute path
cd /var/log

Warning

README.md and readme.md are different files on Linux. Watch capitalization in Git and deploy scripts.

List and Navigate

bash

# Long listing with hidden dotfiles
ls -la
 
# List /etc (system configs — look, rarely edit without reason)
ls /etc

Useful ls options:

Option	Effect
`-l`	Long format (permissions, size, date)
`-a`	Include hidden names starting with `.`
`-h`	Human-readable sizes with `-l`

Create, Copy, Move, Delete

bash

Warning

rm -rf deletes recursively without confirmation. Double-check paths. A typo like rm -rf / tmp/foo can destroy a system—there is no Recycle Bin.

View File Contents

bash

# Whole small file
cat /etc/os-release
 
# Page through large file
less /var/log/syslog
 
# First/last lines
head -n 20 /var/log/syslog
tail -n 20 /var/log/syslog
 
# Follow log live (Ctrl+C to stop)
tail -f /var/log/syslog

Find Files

bash

# Find by name under home (max depth feel with time on big trees)
find ~ -name "*.md" 2>/dev/null
 
# Find directories named logs
find /var -type d -name "log*" 2>/dev/null | head

locate is faster but uses a database updated by updatedb—optional on servers.

Symbolic Links (Concept)

bash

# Create symlink
ln -s /var/log ~/logs
 
# List shows arrow to target
ls -l ~/logs

Symlinks are pointers—similar to Windows shortcuts. Hard links are advanced and rare in daily dev work.

Compare with Windows Habits

Windows	Linux
`dir`	`ls`
`copy`	`cp`
`move`	`mv`
`del`	`rm`
`type file`	`cat file`
Explorer path `C:\Users\...`	`/home/user/...`

Mini Example: Project Folder Layout

Mirror a small Java-style tree by hand:

bash

# Build tree under home
mkdir -p ~/hello-linux/src/main/java
mkdir -p ~/hello-linux/src/test/java
 
# Create a marker file
touch ~/hello-linux/src/main/java/.gitkeep
 
# Show tree (install tree package optional: sudo apt install tree)
find ~/hello-linux

Later, Maven or Gradle generate similar layouts automatically.

FAQ

How do I open the current folder in a GUI file manager?

On desktop Ubuntu: xdg-open . Servers often have no GUI—use SFTP/VS Code Remote SSH instead.

Tab completion?

Press Tab to complete paths and commands; Tab Tab shows choices.

Deleted file recovery?

Assume gone unless you use snapshots/backups. Be careful with rm.

What comes next?

Users, groups, and permissions.