Day-07 Task: Understanding package manager and systemctl

What is a package manager in Linux?

In simpler words, a package manager is a tool that allows users to install, remove, upgrade, configure and manage software packages on an operating system. The package manager can be a graphical application like a software center or a command lines tool like apt-get or Pacman.

What is a package?

A package is usually referred to as an application but it could be a GUI application, command line tool or a software library (required by other software programs). A package is essentially an archive file containing the binary executable, configuration file and sometimes information about the dependencies.

Different kinds of package managers

Package Managers differ based on the packaging system but the same packaging system may have more than one package manager.

For example, RPM has Yum and DNF package managers. For DEB, you have apt-get, aptitude command line-based package managers.

Tasks

1. You have to install docker and Jenkins in your system from your terminal using package managers

   1. Docker Installation

      Before installation run the update command

      #sudo apt update

      

      #sudo apt install docker.io

      

      

      Check status after installation

      #sudo systemctl status docker

      

   2. Jenkins Installation

      Update Your Package Lists Before installing Jenkins, make sure your system has the latest package information.

      #sudo apt update

      

      Browse to Jenkin's site and follow the instructions

      https://pkg.jenkins.io/debian-stable/

      

      # sudo wget -O /usr/share/keyrings/jenkins-keyring.asc \ https://pkg.jenkins.io/debian-stable/jenkins.io-2023.key

      

      # echo deb [signed-by=/usr/share/keyrings/jenkins-keyring.asc] \ https://pkg.jenkins.io/debian-stable binary/ | sudo tee \ /etc/apt/sources.list.d/jenkins.list > /dev/null

      

      #sudo apt-get update

      #sudo apt-get install fontconfig openjdk-11-jre

      #sudo apt-get install jenkins

      

      

      Check Jenkins status.

      #sudo systemctl status jenkins

      

      To start Jenkins

      #sudo systemctl start jenkins

      To stop Jenkins

      #sudo systemctl stop jenkins

      Enable Jenkins on Boot Ensure Jenkins starts automatically on system boot.

      #systemctl enable jenkins

      

      Access Jenkins Web Interface Jenkins runs on port 8080 by default. Open your browser and navigate to http://your_server_ip_or_domain:8080.

      http://3.111.169.99:8080

      If a website is not reachable check the Ec2 instance security group and add a new rule.

      

      

      Unlock Jenkins Retrieve the initial password required to unlock Jenkins.

      #cat /var/lib/jenkins/secrets/initialAdminPassword

      

      e809562f0a5f4eea889025f986185336

      Copy the password and paste it into the Jenkins web interface.

      Customize Jenkins Install suggested plugins or select custom plugins based on your requirements.

      

2. Write a small blog or article to install these tools using package managers on Ubuntu and CentOS.

   Streamlining Your Setup: Installing Essential Tools on Ubuntu and CentOS with Package Managers

   Introduction: Setting up a new environment can be a daunting task, but with the right tools and package managers, you can simplify the process and get up and running in no time. In this guide, we'll walk you through the installation of some essential tools using package managers on both Ubuntu and CentOS.

   1. Ubuntu:

   Update your package lists:

    sudo apt update
   

   1.1 Git:

    sudo apt install git
   

   Git is a version control system that allows you to track changes in your codebase efficiently.

   1.2 Docker:

    sudo apt install docker.io
   

   Docker enables you to containerize applications, making them portable and easy to deploy across different environments.

   2. CentOS:

   Update your package lists:

    sudo yum update
   

   2.1 Git:

    sudo yum install git
   

   Just like on Ubuntu, Git is essential for version control and collaboration on projects.

   2.2 Docker:

    sudo yum install docker
   

   Docker on CentOS provides the same containerization benefits, allowing you to isolate applications and their dependencies.

systemctl and systemd

systemctl is used to examine and control the state of the “systemd” system and service manager. system is a system and service manager for Unix-like operating systems(most of the distributions, not all).

Tasks

1. check the status of the docker service in your system (make sure you completed the above tasks, else docker won't be installed)

   #sudo systemctl status docker

   

2. stop the service Jenkins and post before and after screenshots

   Before

   

   After

   

read about the commands systemctl vs service

eg. systemctl status docker vs service docker status

Both systemctl and service are commands used in Linux systems to manage services, but they have some differences in usage and functionality.

systemctl:

1. Systemd Integration: systemctl is part of the systemd system and service manager, which has become the standard init system for many Linux distributions. It is responsible for managing system processes and services during the system boot process.

2. Extensive Feature Set: systemctl provides a more extensive set of features compared to service. It allows you to control and query the state of services, manage dependencies, view logs, enable or disable services at boot, and more.

3. Unified Interface: systemctl offers a unified interface for interacting with various types of units, not just services. This includes targets, devices, mounts, and sockets.

4. Enhanced Logging: Systemd provides enhanced logging capabilities, and systemctl allows you to view and analyze these logs easily.

service:

1. Traditional SysV Init System: service is associated with the traditional SysV init system, which was the default init system for many older Linux distributions.

2. Simplified Interface: service provides a simplified interface for starting, stopping, restarting, and checking the status of services. It is often used with simple service management tasks.

3. Limited Functionality: While service is straightforward and easy to use, it has limited functionality compared to systemctl. It lacks some of the advanced features provided by systemd.

Common Commands:

• Start a Service:

    systemctl start <service-name>
    service <service-name> start
  

• Stop a Service:

    systemctl stop <service-name>
    service <service-name> stop
  

• Restart a Service:

    systemctl restart <service-name>
    service <service-name> restart
  

• Check Service Status:

    systemctl status <service-name>
    service <service-name> status
  

Summary, systemctl is the more powerful and feature-rich command, especially in systems using systemd, while service is a simpler tool associated with the older SysV init system.