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.

package manager keeps track of what software is installed on your computer, and allows you to easily install new software, upgrade software to newer versions, or remove software that you previously installed.

What is a package?

A package is usually referred to 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 packaging system but same packaging system may have more than one package manager.

Types of Linux Package Managers

All Linux distributions have some form of a package manager. They all handle the same job, though:

• Installing applications

• Upgrading applications

• Managing application dependencies

• Removing applications

• Handling OS updates

Depending on the Linux distribution you are using, it will have a different Linux package manager. Here’s a quick list of each package manager for popular distributions:

Tasks

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

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

Now let’s install the docker

1. Update the apt package index

sudo apt-get update

2. Install the docker

sudo apt install docker.io

3. Run Command to check docker is installed or not

Now let’s install the Jenkins

Reference :https://www.trainwithshubham.com/blog/install-jenkins-on-aws

Step — 1 Install Java

Update your system

sudo apt update

Install java

sudo apt install openjdk-11-jre

Validate Installation

java -version

It should look something 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)

Step — 2 Install Jenkins

Just copy these commands and paste them onto your terminal.

curl -fsSL https://pkg.jenkins.io/debian/jenkins.io.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 binary/ | sudo tee \   /etc/apt/sources.list.d/jenkins.list > /dev/null

sudo apt-get update

sudo apt-get install jenkins

Step -3 Start jenkins

sudo systemctl enable jenkins

sudo systemctl start jenkins

sudo systemctl status jenkins

 sudo cat /var/lib/jenkins/secrets/initialAdminPassword

Step — 4 Open port 8080 from AWS Console using security group section

and using ip:8080 ,we can see jenkins page

systemctl and systemd

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

Tasks

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

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

Before:

After:

3.read about the commands systemctl vs service

eg. systemctl status docker vs service docker status

1.systemctl is a command-line utility used to control and manage the systemd system and service manager on Linux systems. It can be used to start, stop, and restart services, enable and disable them to start at boot, and check the status of services.

2.service is a more generic utility that is used to manage services on a wider range of systems, including those that do not use systemd . If your system uses systemd, you should use systemctl to manage services. If your system does not use systemd ,or if you are not sure, you can use service as a more generic utility.

systemctl commands :

• systemctl start docker

• systemctl stop docker

• systemctl restart docker

• systemctl enable docker

• systemctl disable docker

• systemctl status docker

service commands :

• service docker start

• service docker status

• service docker stop

• service docker restart

Thank you for Reading..!

"Embark on the Journey of Knowledge: Happy Learning Lights Up Your Path."

_Abhi Sagare.