Linux & Bash Scripting – Asecurity Academy

About Course

Course Overview

This comprehensive course takes you from the fundamentals of Linux to advanced Bash scripting, system administration, and automation. Whether you’re a developer, sysadmin, or DevOps engineer, this curriculum will give you the skills to master the Linux command line and write powerful scripts.

Course Content

MODULE 01: Introduction to Linux
Get your Linux environment running and understand the core philosophy that makes Linux unique. This module sets the foundation for everything that follows.

1.1 What is Linux?
History: Unix → GNU → Linux kernel by Linus Torvalds (1991)
Linux distributions: Ubuntu, Fedora, Debian, Arch, CentOS, RHEL
Open source philosophy and the GNU GPL license
Why Linux dominates servers, cloud, and embedded systems
1.2 Setting Up Your Environment
Installing Ubuntu on a VM (VirtualBox / VMware)
WSL2 on Windows — setup and integration
Using macOS Terminal as a Unix environment
Cloud shells: AWS CloudShell, Google Cloud Shell
SSH: connecting to remote servers
1.3 The Linux Filesystem Hierarchy
/ Root of everything
/bin Essential binaries (ls, cp, mv)
/etc System configuration files
/home User home directories
/var Variable data (logs, spool)
/tmp Temporary files
/usr User programs and libraries
/proc Virtual filesystem for processes
/dev Device files
/opt Optional third-party software
1.4 Getting Help
man pages: man ls, man bash
info pages and –help flags
tldr tool for quick command examples
Online resources: man7.org, explainshell.com

MODULE 02: Command Line Fundamentals
Master the essential commands that form the backbone of every Linux task. These tools will become second nature with practice.

2.1 Navigation & File Management
pwd # Print working directory
ls -la # List with hidden files & details
cd /path/to/dir # Change directory
cd ~ # Go to home directory
cd – # Go to previous directory
mkdir -p dir/sub # Create nested directories
rm -rf dir # Remove recursively (use caution!)
cp -r src/ dest/ # Copy directory
mv old new # Move or rename
touch file.txt # Create empty file
2.2 Viewing & Searching Files
cat file.txt # Print file contents
less file.txt # Page through file
head -20 file.txt # First 20 lines
tail -f /var/log/syslog # Follow live log
grep -rn ‘pattern’ dir/ # Recursive search
find / -name ‘*.conf’ # Find by name
wc -l file.txt # Count lines
2.3 Input/Output Redirection
command > output.txt # Redirect stdout
command >> output.txt # Append stdout
command 2> error.txt # Redirect stderr
command 2>&1 # Merge stderr into stdout
command < input.txt # Read stdin from file
cat file | grep ‘term’ # Pipe output to next command
2.4 Wildcards & Globbing
ls *.txt # All .txt files
ls file?.txt # file1.txt, file2.txt, …
ls {a,b,c}.txt # a.txt, b.txt, c.txt
rm log[0-9].txt # log0.txt through log9.txt

MODULE 03: Users, Permissions & File Ownership
Linux is a multi-user system. Understanding permissions is critical for security and system administration.

3.1 Users and Groups
whoami # Current user
id username # UID, GID, groups
sudo useradd -m alice # Create user with home
sudo passwd alice # Set password
sudo usermod -aG sudo alice # Add to group
sudo userdel -r alice # Delete user + home
cat /etc/passwd # User database
cat /etc/group # Group database
3.2 File Permissions
# Octal mode
chmod 755 script.sh # rwxr-xr-x
chmod 644 file.txt # rw-r–r–
chmod 600 key.pem # rw——- (private key)
# Symbolic mode
chmod u+x script.sh # Add execute for owner
chmod g-w file.txt # Remove write for group
chmod o= file.txt # Remove all for others
chmod a+r file.txt # Add read for everyone
# Ownership
chown alice:devs file.txt
chown -R alice:devs /project/
3.3 Special Permissions
chmod +s /usr/bin/prog # SetUID bit
chmod g+s /shared/dir # SetGID bit
chmod +t /tmp # Sticky bit (only owner can delete)
3.4 sudo and su
sudoers file: /etc/sudoers (edit with visudo)
Principle of least privilege
Difference between sudo, su -, and su
sudo -l # List sudo privileges
sudo -u alice command # Run as alice
visudo # Safely edit sudoers

MODULE 04: Bash Scripting — The Basics
Here's where automation begins. Bash scripts let you combine commands, add logic, and build tools. This module covers everything you need to write your first real scripts.

MODULE 05: Bash Scripting — Intermediate
Level up your scripts with functions, arrays, error handling, and string manipulation.

MODULE 06: Text Processing: grep, sed & awk
The trinity of Linux text processing. These tools are indispensable for data extraction, transformation, and reporting.

6.1 grep — Pattern Searching
grep ‘error’ app.log # Basic search
grep -i ‘ERROR’ app.log # Case-insensitive
grep -n ‘error’ app.log # Show line numbers
grep -c ‘error’ app.log # Count matches
grep -v ‘debug’ app.log # Invert (exclude)
grep -r ‘TODO’ ./src/ # Recursive
grep -l ‘pattern’ *.txt # Files with matches
grep -A 3 -B 3 ‘error’ app.log # 3 lines context
grep -E ‘^[0-9]{4}-‘ app.log # Extended regex
grep -P ‘\d{1,3}\.\d{1,3}’ file # Perl regex
6.2 sed — Stream Editor
# Substitution
sed ‘s/old/new/’ file.txt # First occurrence per line
sed ‘s/old/new/g’ file.txt # All occurrences
sed ‘s/old/new/gi’ file.txt # Case-insensitive
sed -i ‘s/old/new/g’ file.txt # Edit file in-place
sed -i.bak ‘s/old/new/g’ file.txt # Backup before editing
# Delete lines
sed ‘/pattern/d’ file.txt # Delete matching lines
sed ‘5d’ file.txt # Delete line 5
sed ‘1,3d’ file.txt # Delete lines 1-3
# Print specific lines
sed -n ‘10,20p’ file.txt # Print lines 10-20
sed -n ‘/start/,/end/p’ file.txt # Between patterns
# Insert/append
sed ‘3i\New line before line 3’ file.txt
sed ‘3a\New line after line 3’ file.txt
6.3 awk — Pattern Scanning & Processing

MODULE 07: Process & System Management
Understand how Linux manages processes, system resources, and services. Essential skills for any sysadmin or DevOps role.

7.1 Process Management
ps aux # All processes
ps -eo pid,ppid,cmd,%cpu,%mem –sort=-%cpu
top # Real-time view
htop # Interactive (install first)
pgrep nginx # PID by name
kill 1234 # SIGTERM (graceful)
kill -9 1234 # SIGKILL (force)
killall nginx # Kill by name
pkill -u alice # Kill by user
# Background jobs
command & # Run in background
jobs # List background jobs
fg %1 # Bring job 1 to foreground
bg %1 # Resume in background
nohup command & # Persist after logout
screen / tmux # Terminal multiplexers
7.2 Systemd & Service Management
# systemctl
systemctl status nginx # Check status
systemctl start|stop|restart nginx
systemctl enable nginx # Enable on boot
systemctl disable nginx # Disable on boot
systemctl list-units –type=service
# Logs with journald
journalctl -u nginx # Logs for nginx
journalctl -f # Follow all logs
journalctl –since “1 hour ago”
journalctl -p err # Errors only
7.3 System Resources
free -h # Memory usage
df -h # Disk space
du -sh /var/log/ # Directory size
iostat -x 1 5 # Disk I/O
vmstat 1 5 # System stats
lscpu # CPU info
lsblk # Block devices
netstat -tulpn # Open ports
ss -tulpn # Modern netstat
lsof -i :80 # Processes on port 80
7.4 Scheduling with cron
# crontab syntax: min hour day month weekday command
crontab -e # Edit your crontab
crontab -l # List crontab
# Examples
0 2 * * * /backup.sh # Daily at 2am
*/15 * * * * /check-health.sh # Every 15 minutes
0 9 * * 1 /weekly-report.sh # Mondays at 9am
0 0 1 * * /monthly-cleanup.sh # Monthly
@reboot /start-services.sh # On system boot
# System-wide cron
/etc/cron.d/
/etc/cron.daily/
/etc/cron.weekly/

MODULE 08: Networking & SSH
Configure networking, diagnose issues, and master SSH for secure remote access and tunneling.

8.1 Networking Fundamentals
ip addr show # Interface & IP addresses
ip route show # Routing table
ping -c 4 google.com # ICMP test
traceroute google.com # Path to host
dig google.com # DNS lookup
nslookup google.com # DNS lookup (older)
curl -v https://api.com # HTTP requests
wget -O file.html https://example.com
nc -zv host 22 # Port check (netcat)
8.2 SSH Mastery
# Key generation
ssh-keygen -t ed25519 -C “your@email.com”
# Copy key to server
ssh-copy-id user@server
# Connect
ssh user@server
ssh -p 2222 user@server # Custom port
ssh -i ~/.ssh/mykey user@server # Specific key
# SSH config file: ~/.ssh/config
Host myserver
HostName 192.168.1.100
User alice
Port 2222
IdentityFile ~/.ssh/mykey
ServerAliveInterval 60
ssh myserver # Now just this!
# Tunnels
ssh -L 8080:localhost:80 user@server # Local forward
ssh -R 9090:localhost:3000 user@server # Remote forward
ssh -D 1080 user@server # SOCKS proxy
8.3 File Transfer
scp file.txt user@server:/remote/path/
scp -r dir/ user@server:/remote/dir/
rsync -avz –progress src/ user@server:/dest/
rsync -avz –delete src/ dest/ # Mirror (delete extra)
rsync –exclude=’*.log’ src/ dest/

MODULE 09: Advanced Bash Scripting
Build robust, production-grade scripts with advanced patterns including getopts, here documents, process substitution, and more.

MODULE 10: Package Management & Software Installation
Install, update, and manage software across the most popular Linux distributions.

10.1 APT (Debian/Ubuntu)
sudo apt update # Refresh package index
sudo apt upgrade # Upgrade all packages
sudo apt install nginx git curl # Install packages
sudo apt remove nginx # Remove (keep config)
sudo apt purge nginx # Remove + config
sudo apt autoremove # Remove orphans
apt search keyword # Search packages
apt show nginx # Package details
dpkg -l | grep nginx # Check if installed
dpkg -L nginx # List installed files
10.2 YUM/DNF (RHEL/Fedora/CentOS)
sudo dnf update # Update all
sudo dnf install nginx # Install
sudo dnf remove nginx # Remove
sudo dnf search keyword # Search
sudo dnf info nginx # Details
sudo dnf group install “Development Tools”
rpm -qa | grep nginx # List installed RPMs
10.3 Compiling from Source

MODULE 11: Security Hardening & Best Practices
Secure your Linux systems and write scripts that follow security best practices to protect against common attack vectors.

11.1 SSH Hardening
# /etc/ssh/sshd_config best practices
PermitRootLogin no
PasswordAuthentication no
PubkeyAuthentication yes
AllowUsers alice bob
Port 2222 # Non-standard port
MaxAuthTries 3
LoginGraceTime 60
ClientAliveInterval 300
ClientAliveCountMax 2
11.2 Firewall with ufw / iptables
# ufw (Uncomplicated Firewall)
sudo ufw enable
sudo ufw default deny incoming
sudo ufw default allow outgoing
sudo ufw allow 2222/tcp # SSH on custom port
sudo ufw allow 80/tcp
sudo ufw allow 443/tcp
sudo ufw status verbose
# Rate limiting (anti-brute force)
sudo ufw limit 2222/tcp
11.3 File Integrity & Auditing
# Find world-writable files
find / -perm -002 -type f 2>/dev/null
# Find SUID/SGID files
find / -perm -4000 -o -perm -2000 2>/dev/null
# auditd — system call auditing
auditctl -w /etc/passwd -p wa -k passwd_changes
auditctl -w /etc/sudoers -p wa -k sudoers_changes
auditd -l # List rules
ausearch -k passwd_changes # Search audit log
# File integrity with AIDE
sudo aide –init
sudo aide –check
11.4 Secrets Management in Scripts
# NEVER hardcode credentials in scripts
# BAD: DB_PASS=”supersecret123″ # NEVER DO THIS
# GOOD: Environment variables export DB_PASS=”$(vault read -field=pass secret/db)”
# GOOD: Read from secure file with strict perms DB_PASS=$(cat /etc/myapp/db.pass) # chmod 400 this file
# GOOD: Prompt at runtime read -sp “Database password: ” DB_PASS export DB_PASS
# Use .env files — never commit them set -a; source .env; set +a # Load .env

MODULE 12: DevOps Automation & Real-World Projects
Apply everything you've learned in real-world scenarios. Build production-quality automation scripts and integrate with modern DevOps tools.

About Course

What Will You Learn?

Course Content

MODULE 01: Introduction to Linux Get your Linux environment running and understand the core philosophy that makes Linux unique. This module sets the foundation for everything that follows.

1.1 What is Linux?

History: Unix → GNU → Linux kernel by Linus Torvalds (1991)

Linux distributions: Ubuntu, Fedora, Debian, Arch, CentOS, RHEL

Open source philosophy and the GNU GPL license

Why Linux dominates servers, cloud, and embedded systems

1.2 Setting Up Your Environment

Installing Ubuntu on a VM (VirtualBox / VMware)

WSL2 on Windows — setup and integration

Using macOS Terminal as a Unix environment

Cloud shells: AWS CloudShell, Google Cloud Shell

SSH: connecting to remote servers

1.3 The Linux Filesystem Hierarchy

/ Root of everything

/bin Essential binaries (ls, cp, mv)

/etc System configuration files

/home User home directories

/var Variable data (logs, spool)

/tmp Temporary files

/usr User programs and libraries

/proc Virtual filesystem for processes

/dev Device files

/opt Optional third-party software

1.4 Getting Help

man pages: man ls, man bash

info pages and –help flags

tldr tool for quick command examples

Online resources: man7.org, explainshell.com

MODULE 02: Command Line Fundamentals Master the essential commands that form the backbone of every Linux task. These tools will become second nature with practice.

2.1 Navigation & File Management

pwd # Print working directory

ls -la # List with hidden files & details

cd /path/to/dir # Change directory

cd ~ # Go to home directory

cd – # Go to previous directory

mkdir -p dir/sub # Create nested directories

rm -rf dir # Remove recursively (use caution!)

cp -r src/ dest/ # Copy directory

mv old new # Move or rename

touch file.txt # Create empty file

2.2 Viewing & Searching Files

cat file.txt # Print file contents

less file.txt # Page through file

head -20 file.txt # First 20 lines

tail -f /var/log/syslog # Follow live log

grep -rn ‘pattern’ dir/ # Recursive search

find / -name ‘*.conf’ # Find by name

wc -l file.txt # Count lines

2.3 Input/Output Redirection

command > output.txt # Redirect stdout

command >> output.txt # Append stdout

command 2> error.txt # Redirect stderr

command 2>&1 # Merge stderr into stdout

command < input.txt # Read stdin from file

cat file | grep ‘term’ # Pipe output to next command

2.4 Wildcards & Globbing

ls *.txt # All .txt files

ls file?.txt # file1.txt, file2.txt, …

ls {a,b,c}.txt # a.txt, b.txt, c.txt

rm log[0-9].txt # log0.txt through log9.txt

MODULE 03: Users, Permissions & File Ownership Linux is a multi-user system. Understanding permissions is critical for security and system administration.

3.1 Users and Groups

whoami # Current user

id username # UID, GID, groups

sudo useradd -m alice # Create user with home

sudo passwd alice # Set password

sudo usermod -aG sudo alice # Add to group

sudo userdel -r alice # Delete user + home

cat /etc/passwd # User database

cat /etc/group # Group database

3.2 File Permissions

# Octal mode

chmod 755 script.sh # rwxr-xr-x

chmod 644 file.txt # rw-r–r–

chmod 600 key.pem # rw——- (private key)

# Symbolic mode