DEV Community: JZTN

Ubuntu CLI cheat sheet

JZTN — Wed, 05 Feb 2025 07:12:10 +0000

System

System information

# Displays all system information.
uname -a
# Shows current hostname and related details.
hostnamectl
# Lists CPU architecture information.
lscpu
# Shows system time.
timedatectl status

System monitoring and management

# Displays real-time system processes.
top
# An interactive process viewer (needs installation).
htop
# Shows disk usage in a human-readable format.
df -h
# Displays free and used memory in MB.
free -m
# Terminates a process.
kill <process id>

Running commands

# Runs command in the background.
[command] &
# Displays background commands.
jobs
# Brings command to the foreground.
fg <command number>

Service management

# Starts a service.
sudo systemctl start <service>
# Stops a service.
sudo systemctl stop <service>
# Checks the status of a service.
sudo systemctl status <service>
# Reloads a service’s configuration without interrupting its operation.
sudo systemctl reload <service>
# Follows the journal, showing new log messages in real time.  
journalctl -f
# Displays logs for a specific systemd unit.
journalctl -u <unit_name>

Cron jobs and scheduling

# Edits cron jobs for the current user.
crontab -e
# Lists cron jobs for the current user.
crontab -l

Files

File management

# Lists files and directories.
ls
# Creates an empty file or updates the last accessed date.
touch <filename>
# Copies files from source to destination.
cp <source> <destination>
# Moves files or renames them.
mv <source> <destination>
# Deletes a file.
rm <filename>

Directory navigation

# Displays the current directory path.
pwd
# Changes the current directory.
cd <directory>
# Creates a new directory.
mkdir <dirname>

File permissions and ownership

# Changes file permissions.
chmod [who][+/-][permissions] <file>
# Makes a file executable by its owner.
chmod u+x <file>
# Changes file owner and group.
chown [user]:[group] <file>

Searching and finding

# Finds files and directories.
find [directory] -name <search_pattern>
# Searches for a pattern in files.
grep <search_pattern> <file>

Archiving and compression

# Compresses files into a tar.gz archive.
tar -czvf <name.tar.gz> [files]
# Extracts a compressed tar archive.
tar -xvf <name.tar.[gz|bz|xz]> [destination]

Text editing and processing

# Opens a file in the Nano text editor.
nano [file]
# Displays the contents of a file.
cat <file>
# Displays the paginated content of a file.
less <file>
# Shows the first few lines of a file.
head <file>
# Shows the last few lines of a file.
tail <file>
# Prints every line in a file.
awk '{print}' [file]

Packages

Package management (APT)

# Installs a package.
sudo apt install <package>
# Reinstalls a broken package.
sudo apt install -f --reinstall <package>
# Searches for APT packages.
apt search <package>
# Lists available package versions.
apt-cache policy <package>
# Updates package lists.
sudo apt update
# Upgrades all upgradable packages.
sudo apt upgrade
# Removes a package.
sudo apt remove <package>
# Removes a package and all its configuration files.
sudo apt purge <package>

Package management (Snap)

# Searches for Snap packages.
snap find <package>
# Installs a Snap package.
sudo snap install <snap_name>
# Removes a Snap package.
sudo snap remove <snap_name>
# Updates all installed Snap packages.
sudo snap refresh
# Lists all installed Snap packages.
snap list
# Displays information about a Snap package.
snap info <snap_name>

Users & Groups

User management

# Shows which users are logged in.
w
# Creates a new user.
sudo adduser <username>
# Deletes a user.
sudo deluser <username>
# Sets or changes the password for a user.
sudo passwd <username>
# Switches user.
su <username>
# Locks a user account.
sudo passwd -l <username>
# Unlocks a user password.
sudo passwd -u <username>
# Sets user password expiration date.
sudo chage <username>

Group management

# Displays user and group IDs.
id [username]
# Shows the groups a user belongs to.
groups [username]
# Creates a new group.
sudo addgroup <groupname>
# Deletes a group.
sudo delgroup <groupname>

Networking

Networking Commands

# Displays network interfaces and IP addresses.
ip addr show
# Shows network statistics.
ip -s link
# Shows listening sockets.
ss -l
# Pings a host and outputs results.
ping <host>

Netplan Configuration

# Displays the current Netplan configuration.
cat /etc/netplan/*.yaml
# Tests a new configuration for a set period of time.
sudo netplan try
# Applies the current Netplan configuration.
sudo netplan apply

Firewall Management

# Displays the status of the firewall.
sudo ufw status
# Enables the firewall.
sudo ufw enable
# Disables the firewall.
sudo ufw disable
# Allows traffic on a specific port or service.
sudo ufw allow <port/service>
# Denies traffic on a specific port or service.
sudo ufw deny <port/service>
# Deletes an existing rule.
sudo ufw delete allow/deny <port/service>

SSH and Remote Access

# Connects to a remote host via SSH.
ssh <user@host>
# Securely copies files between hosts.
scp <source> <user@host>:<destination>

LXD

LXD is a modern, secure, and powerful tool that provides a unified experience for
running and managing containers or virtual machines. Visit LXD Official Site for more information.

Initialization

# Initializes LXD before first use.
lxd init

Creating Instances

# Creates a LXC system container (without starting it).
lxc init ubuntu:22.04 <container_name>

# Creates and starts a LXC system container.
lxc launch ubuntu:24.04 <container_name>

# Creates and starts a virtual machine.
lxc launch ubuntu:22.04 <vm_name> --vm

Managing Instances

# Lists instances.
lxc list

# Shows status information about an instance.
lxc info <instance>

# Starts an instance.
lxc start <instance>

# Stops an instance.
lxc stop <instance> [--force]

# Deletes an instance.
lxc delete <instance> [--force|--interactive]

Accessing Instances

# Runs a command inside an instance.
lxc exec <instance> -- <command>

# Gets shell access to an instance (if bash is installed).
lxc exec <instance> -- bash

# Gets console access to an instance.
lxc console <instance> [flags]

# Pulls a file from an instance.
lxc file pull <instance>/<instance_filepath> <local_filepath>

# Pushes a file to an instance.
lxc file push <local_filepath> <instance>/<instance_filepath>

Using Projects

# Creates a project.
lxc project create <project> [--config <option>]

# Configures a project.
lxc project set <project> <option>

# Switches to a project.
lxc project switch <project>

Ubuntu Pro

Ubuntu Pro delivers 10 years of expanded security coverage on top of Ubuntu’s Long Term
Support (LTS) commitment in addition to management and compliance tooling. Visit Ubuntu Pro to register for free on up to five machines.

Activating Ubuntu Pro

# Attaches your machine to Ubuntu Pro using a specific token.
sudo pro attach <token>

Managing Services

# Displays the status of all Ubuntu Pro services.
sudo pro status

# Enables a specific Ubuntu Pro service, like ESM, FIPS, or Livepatch.
sudo pro enable <service>

# Disables a specific Ubuntu Pro service.
sudo pro disable <service>

Extended Security Maintenance (ESM)

# Activates Extended Security Maintenance for infrastructure packages.
sudo pro enable esm-infra

# Activates ESM for applications, extending security coverage.
sudo pro enable esm-apps

Livepatch Service

# Enables the Livepatch service, which applies critical kernel patches without rebooting.
sudo pro enable livepatch

FIPS Mode

# Enables FIPS (Federal Information Processing Standards) mode, enforcing strict cryptographic standards.
sudo pro enable fips

Updating Configuration

# Refreshes the Ubuntu Pro state to ensure the latest configuration and services are in place.
sudo pro refresh

Detaching Ubuntu Pro

# Detaches the machine from Ubuntu Pro, disabling all services.
sudo pro detach

This is a complete and structured Ubuntu CLI cheat sheet.

5 Cybersecurity Projects Every Computer Science Student Should Try

JZTN — Tue, 04 Feb 2025 13:02:24 +0000

As a computer science student passionate about cybersecurity, I’ve discovered that hands-on projects are the best way to learn. Theory is essential, but nothing beats the experience of building something tangible. In this guide, I’ll share five practical projects that will help you build a strong foundation in cybersecurity while creating an impressive portfolio.

Whether you’re a beginner or looking to sharpen your skills, these projects will challenge you and deepen your understanding of key cybersecurity concepts. Let’s dive in!

1. Network Packet Sniffer

Every cybersecurity enthusiast should start by understanding network traffic. Building a packet sniffer is an excellent way to learn the fundamentals of network protocols and data transmission.

What You’ll Learn:

Network protocols (TCP/IP, UDP)
Packet structure and analysis
Socket programming
Traffic monitoring techniques
Tools & Technologies:

Python with Scapy library
Wireshark (for verification)
Basic networking knowledge
The beauty of this project lies in its simplicity to start but vast potential for expansion. Begin with capturing basic HTTP traffic, then advance to protocol analysis and packet filtering.

2. Simple Intrusion Detection System (IDS)

Creating a basic IDS helps you understand how to detect potential security threats in real-time. This project is a great way to explore system monitoring and threat detection.

Key Features to Implement:

Log file monitoring
Pattern matching for known attacks
Alert system for suspicious activities
Basic threat classification
Learning Outcomes:

System log analysis
Regular expressions
Real-time monitoring
Threat detection algorithms
Start small by monitoring SSH login attempts, then gradually add more detection rules and features.

3. Password Strength Checker

While it might sound basic, building a comprehensive password validator teaches crucial security concepts. This project is a great way to explore cryptography and user input validation.

Implementation Aspects:

Multiple validation criteria
Dictionary attack prevention
Hash function implementation
Password entropy calculation
Skills Gained:

Cryptography basics
Security best practices
User input validation
Data protection standards
This project perfectly combines security theory with practical application.

4. File Integrity Monitor

A file integrity monitoring system teaches you about system security and change detection. This is a critical skill for identifying unauthorized modifications to files.

Core Features:

File hash calculation
Real-time monitoring
Change logging
Alert system
Technical Learning:

Cryptographic hashing
File system operations
Background processes
Database management
This project demonstrates how to detect unauthorized system modifications — a crucial security skill.

5. Security Information and Event Management (SIEM) Lite

Creating a simplified SIEM system brings together multiple security concepts. This project is ideal for understanding log aggregation, event correlation, and security analytics.

Project Components:

Log aggregation
Event correlation
Basic analytics
Reporting system
Benefits:

System integration experience
Data analysis skills
Alert management
Security event handling
While not as complex as commercial SIEM solutions, this project teaches fundamental security monitoring principles.

Getting Started Tips
Set Up a Lab Environment
Use virtual machines to create isolated testing environments.
Practice safe testing and avoid targeting unauthorized systems.
Version Control
Use Git from day one to track your progress.
Document your work and share your code responsibly.
Security First
Always test in isolated environments.
Follow ethical guidelines and respect privacy.
Learn from the Community
Join cybersecurity forums and communities.
Participate in Capture the Flag (CTF) challenges.
Share your experiences and learn from others.
Conclusion
These five projects provide a solid foundation in practical cybersecurity. Remember, the goal isn’t just to complete them, but to understand the underlying security principles. Start with basic implementations and gradually add complexity as your understanding grows.

What’s next? Pick a project that interests you most and start coding. Each project can be as simple or complex as you make it — the key is to begin and keep improving.

Happy coding and stay secure! 🛡️

About the Author:
I’m a cybersecurity enthusiast and computer science student passionate about sharing experiences and knowledge with the community. Follow me for more insights into cybersecurity, programming, and technology!