Day 7 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 line tool like apt-get or pacman.

You’ll often find me using the term ‘package’ in tutorials and articles, To understand package manager, you must understand what a package is.

🔶 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.

APT package manager
APT (Advanced Package Tool) is a package management system used in Debian-based Linux distributions, such as Debian itself, Ubuntu, and Linux Mint. It is designed to simplify the installation, upgrading, and removal of software packages on a Linux system.

DNF package manager
DNF (Dandified Yum) is a package manager used in Fedora, RHEL (Red Hat Enterprise Linux), CentOS, and other RPM-based Linux distributions. It is the successor to the Yum package manager and offers enhanced performance, improved dependency resolution, and better version-locking capabilities.

YUM package manager
YUM (Yellowdog Updater Modified) is a package manager used in RPM-based Linux distributions, such as CentOS, Fedora, and Red Hat Enterprise Linux (RHEL). It provides an easy way to manage software packages by handling installation, updating, and removal of packages, as well as resolving dependencies between packages.

ZYpp package manager
ZYpp (Zypper Package Manager) is a package management tool used in openSUSE and SUSE Linux Enterprise distributions. It is designed to handle the installation, updating, and removal of software packages, as well as dependency resolution and repository management.

🔶 Task 1: Install docker and Jenkins in your system from your terminal using package managers.

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

Installing Docker
Before you install Docker Engine for the first time on a new host machine, you need to set up the Docker repository. Afterward, you can install and update Docker from the repository.
Set up the repository
1. Update the apt package index and install packages to allow apt to use a repository over HTTPS:

1.  sudo apt-get update
    sudo apt-get install ca-certificates curl gnupg
   

   1. Add Docker’s official GPG key:

    sudo install -m 0755 -d /etc/apt/keyrings
    curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo gpg --dearmor -o /etc/apt/keyrings/docker.gpg
    sudo chmod a+r /etc/apt/keyrings/docker.gpg

1. Use the following command to set up the repository:

    echo \
      "deb [arch="$(dpkg --print-architecture)" signed-by=/etc/apt/keyrings/docker.gpg] https://download.docker.com/linux/ubuntu \
      "$(. /etc/os-release && echo "$VERSION_CODENAME")" stable" | \
      sudo tee /etc/apt/sources.list.d/docker.list > /dev/null

Steps to Install Docker Engine

1. Update the apt package index:

    sudo apt-get update
   

2. Install Docker Engine, containers, and Docker Compose.

    sudo apt-get install docker-ce docker-ce-cli containerd.io docker-buildx-plugin docker-compose-plugin
   

3. Verify that the Docker Engine installation is successful by running the hello-world image.

    sudo docker run hello-world
   

   

Installing Jenkins
First of all, install Java:

    #Update your system
    sudo apt update
    #Install java
    sudo apt install openjdk-11-jre
    #Validate Installation
    java -version
    #It should look somethStep - 1 Install Javaing like this
    #openjdk version "11.0.12" 2021-07-20 OpenJDK Runtime Environment (build 11.0.12+7-post-Debian-2) OpenJDK 64-Bit Server VM (build 11.0.12+7-post-Debian-2, mixed mode, sharing)

To install Jenkins:

    curl -fsSL https://pkg.jenkins.io/debian-stable/jenkins.io-2023.key | sudo tee \
      /usr/share/keyrings/jenkins-keyring.asc > /dev/null
    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 jenkins

To Start Jenkins:

    #Enable the Jenkins service to start
    sudo systemctl enable jenkins
    #To start jenkins
    sudo systemctl start jenkins
    #To check the status of jenkins
    sudo systemctl status jenkins

Browse to http://<server-ip>:8080 (or whichever port you configured for Jenkins when installing it) and wait until the Unlock Jenkins page appears.

    #Use to generate passward to unlock
    sudo cat /var/lib/jenkins/secrets/initialAdminPassword

Getting Started

Create First Admin User

Instance Configuration

Jenkins is ready

Jenkins Dashboard

🔶 systemctl and systemd

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

🔶 Task 3: Check the status of the docker service in your system (make sure you completed the above tasks, else docker won't be installed)

sudo service docker status

🔶 Task 4: Stop the service Jenkins and post before and after screenshots

#To check the status of jenkins
sudo systemctl status jenkins

#To Stop the jenkins
 sudo systemctl stop jenkins

🔶 Task 5: Read about the commands systemctl vs service

eg. systemctl status docker vs service docker status

systemctl and service are two different commands used in Linux to manage and control system services. They serve similar purposes but have some differences in their usage and capabilities.

1. systemctl:

   • systemctl is a command-line tool used to control the systemd system and service manager, which is the default initialization system in most modern Linux distributions.

   • It allows users to start, stop, restart, enable, disable, and manage system services, targets (similar to runlevels), and other units managed by systemd.

   • The syntax for using systemctl is as follows:

       systemctl [command] [service_name]
     

   • Example commands using systemctl:

     • Start a service: systemctl start service_name

     • Stop a service: systemctl stop service_name

     • Restart a service: systemctl restart service_name

     • Enable a service to start at boot: systemctl enable service_name

     • Disable a service from starting at boot: systemctl disable service_name

     • Check the status of a service: systemctl status service_name

2. service:

   • service is a legacy command used to control system services in older Linux distributions that do not use systemd as their default initialization system. It is also used in some current distributions for compatibility purposes.

   • While it can perform similar actions to systemctl, its syntax and capabilities are more limited.

   • The syntax for using service is as follows:

       service [service_name] [command]
     

   • Example commands using service:

     • Start a service: service service_name start

     • Stop a service: service service_name stop

     • Restart a service: service service_name restart

     • Enable a service to start at boot: service service_name enable

     • Disable a service from starting at boot: service service_name disable

     • Check the status of a service: service service_name status

In modern Linux distributions that use systemd, it is recommended to use systemctl for managing services, as it offers more features and better integration with the initialization system. However, in some cases, you may still encounter service being used for compatibility reasons or on systems that have not yet adopted systemd.

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