Key Uses of Linux:

1. Server Management:

   • Linux is extensively used to run servers due to its stability, security, and flexibility. Many web servers, database servers, and cloud systems rely on Linux.

2. Software Development:

   • Programmers and developers prefer Linux for its versatility and compatibility with various programming languages and tools. It also allows customization, automation with shell scripting, and has strong support for development environments.

3. Networking and Security:

   • Linux provides strong networking capabilities, making it popular among network administrators. Many cybersecurity professionals also use Linux for its access to various security tools and configurations.

4. Embedded Systems and IoT:

   • Due to its efficiency and low resource requirements, Linux is common in embedded systems and IoT devices, like smart thermostats, automotive infotainment systems, and industrial control systems.

5. Education and Research:

   • Linux is often used in research and academia, where high-performance computing, data science, and simulations require a flexible, open platform.

6. Personal Use:

   • Many users choose Linux for personal computing because it is open-source, meaning it’s free, and is highly customizable, allowing users to tailor it to their needs.

Advantages of Linux:

• Security: Linux is generally more secure than many other operating systems due to its user permissions and open-source nature.

• Stability and Performance: Linux systems are known for running efficiently for long periods without crashing.

• Open Source and Free: Being open source, Linux can be modified, and it’s typically free, saving costs.

• Customization: Users can modify Linux to fit their specific needs, from the desktop environment to the kernel itself.

• Community Support: Linux has a large community that supports development, troubleshooting, and innovation.

• Install a package:
  sudo apt install <package-name>

• Remove a package:
  sudo apt remove <package-name>

• Install nginx:
  sudo apt install nginx

• Check nginx version:
  nginx -v

File and Directory Management

• List files in a directory:
  ls

• List files with detailed information:
  ls -lh

• Change directory:
  cd <directory-name>

• Create a new directory:
  mkdir <directory-name>

• Remove an empty directory:
  rmdir <directory-name>

• Remove a file:
  rm <file-name>

• Create an empty file:
  touch <file-name>

• Show current directory:
  pwd

User Management

• Add a new user:
  sudo adduser <username>

• Change file owner:
  sudo chown <new-owner> <file-name>

• Change file group:
  sudo chgrp <new-group> <file-name>

Permissions

• Change file permissions:
  sudo chmod <permissions> <file-name>

Process Management

• View running processes:
  ps

• View Docker processes:
  docker ps

Docker Commands

• Pull a Docker image:
  docker pull <image-name>

• Run a Docker container:
  docker run <image-name>

• List Docker images:
  docker images

Networking

• Check system status:
  sudo systemctl status <service-name>

• Start a service:
  sudo systemctl start <service-name>

• Enable a service to start at boot:
  sudo systemctl enable <service-name>

Miscellaneous

• Clear the terminal screen:
  clear

• Open a file in a text editor:
  vim <file-name>

Scheduling Tasks

• Edit crontab:
  crontab -e

• List crontab entries:
  crontab -l

Backup and Archive

• Create a zip archive:
  zip <archive-name>.zip <file1> <file2>

• List zip contents:
  unzip -l <archive-name>.zip

Version Checking

• Check Java version:
  java -version

• Jenkins Installation and Setup

  • Install Jenkins
    sudo apt update
sudo apt install jenkins

  • Clean Up Package Cache
    sudo apt clean

  • Start and Enable Jenkins Service
    sudo systemctl start jenkins
sudo systemctl enable jenkins

  • Check Jenkins Service Status
    sudo systemctl status jenkins

  • View Jenkins Log
    sudo cat /var/log/jenkins/jenkins.log

  • View Detailed Jenkins Log
    sudo journalctl -xe -u jenkins

  • Restart Jenkins Service
    sudo systemctl restart jenkins

  • Stop Jenkins Service
    sudo systemctl stop jenkins

Docker Commands

• Enable Docker to Start on Boot
  systemctl enable docker

• Check Docker Service Status
  systemctl status docker

• View Docker Logs
  journalctl -u docker

Git Configuration and Repository Setup

• Configure Git Username and Email
  git config --global user.name "Vani019"
git config --global user.email "shivani019singh@gmail.com"

• View Git Configuration
  git config --list

• Initialize Git Repository
  mkdir github
cd github
git init

• Set Default Branch Name
  git config --global init.defaultBranch main

• Add Remote Repository
  git remote add origin https://github.com/Vani019/Test.git

• Create Subdirectories and Add a File
  mkdir -p Devops/Git
echo "Created new directory" > Devops/Git/GitTest1.txt

• Add and Commit Changes
  git add .
git commit -m "Initial commit with .txt file"

• Push to Remote Repository
  git push -u origin main

• Switch to a New Branch
  git checkout -b main

• Check Git Status
  git status

In summary, this cheat sheet provides a quick reference for essential commands to install, configure, and manage Jenkins, Docker, and Git. The Jenkins section covers steps to install, start, enable, and check the status of the Jenkins service, as well as viewing and managing logs. Docker commands include enabling Docker to start on boot, checking its status, and viewing logs, which helps ensure your Docker environment runs smoothly. The Git section details key setup commands such as configuring user information, initializing repositories, setting branch names, and managing commits and branches, which is crucial for efficient version control.

With these commands, you can set up and maintain continuous integration with Jenkins, containerization with Docker, and streamlined version control with Git—providing a solid foundation for DevOps and collaborative software development.