Today we will learn about Package managers and System services, and also have tasks for this topic.

What is a Package Manager in Linux?
Package Manager is a tool that can Install, remove, update or manage Packages on Operating system. It also brings dependencies for that package if needed.

What is a Package?
Package is a bundle or a bunch of files, it contains everything that need to run a Software like it’s code, configuration files, libraries, etc. When you download any software, it gives an archive file and when you extract it you see that different files are present in it, that archive file is nothing but a package.

Different Kinds of Package Managers
There are so many types of Package Manager

System package managers :
These are in-built tools to manage packages, like

APT : For Ubuntu and Debian-based distributions.

Eg. sudo apt install <package-name>

DNF/YUM : For Red Hat-based distributions like Fedora, CentOS

Eg. sudo dnf install <package-name>

sudo yum install <package-name>

Pacman : For Arch Linux

Eg. sudo pacman -S <package-name>
Universal Package Managers : These managers are for all distributions like

Snap : Made by Ubuntu but work on all distributions

Eg. sudo snap install <package-name>

Flatpak : Work on all distributions

Eg. flatpak install <remote-name> <package-name>
Manual Install Tools : These are used when packages are not available in repositories

DPKG : For .deb extension files

Eg. sudo dpkg -i <package-name.deb>

RPM : For .rpm files

Eg. sudo rpm -ivh <package-name.rpm>

Task 1 : Install Docker and Jenkins

- Install Docker and Jenkins on your system from your terminal using package managers.

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

Solution :

For Ubuntu

Installing Docker

First update your system, updating your system before any installation is good practice

sudo apt update
sudo apt upgrade -y

Install required dependencies, These packages allow system to download Docker securely and manage repositories

sudo apt install -y apt-transport-https ca-certificates curl software-properties-common

Add Docker’s GPG key for secure package verification

curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo gpg --dearmor -o /usr/share/keyrings/docker-archive-keyring.gpg

Add Docker’s Repository to your system’s package manager for stable updates

echo "deb [arch=$(dpkg --print-architecture) signed-by=/usr/share/keyrings/docker-archive-keyring.gpg] https://download.docker.com/linux/ubuntu $(lsb_release -cs) stable" | sudo tee /etc/apt/sources.list.d/docker.list > /dev/null

And then finally install Docker after again one time updating your system

sudo apt update
sudo apt install -y docker-ce docker-ce-cli containerd.io

These will install :

docker-ce: The main Docker engine.
docker-ce-cli: Command-line interface tools for Docker.
containerd.io: A container runtime.

Check if downloaded successfully

docker --version

it should give something like this Docker version 27.3.1, build ce12230 means it is installed.

Installing Jenkins

Install java, because jenkins need java to run

sudo apt install -y openjdk-17-jdk

Add jenkins repository key, this will download and stores GPG key

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

Add jenkins repository

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

And finally install jenkins after updating system one more time

sudo apt update
sudo apt install -y jenkins

Start and enable jenkins service

sudo systemctl start jenkins && sudo systemctl enable jenkins

Now if you are on your local machine then go to browser and type http://localhost:8080

Steps if you are on instance (optional-case)

And if you are on your AWS instance even if on your local machine but connected to instance then go to your Instances → Instance ID → Security → Security groups → Edit inbound rules → Add rule → In port range type 8080 and select Source type as Anywhere-IPv4 → Save rules and then again go to Instances → Insatnce ID → Public IPv4 address (copy that address) and paste it in between below line

Eg. http://15.207.98.161:8080

http://<Public IPv4 address>:8080

After searching this, you’ll be able to see Jenkins web interface on your browser just like this …

as you can see it is asking for a Administrator password, for this password copy that red highlighted path Eg. /var/lib/jenkins/secrets/initialAdminPassword

For CentOS

Installing Docker

First, update your system. Updating your system before any installation is good practice.

sudo yum update -y

Add the Docker repository

sudo yum install -y yum-utils
sudo yum-config-manager --add-repo https://download.docker.com/linux/centos/docker-ce.repo

Install Docker

sudo yum install -y docker-ce docker-ce-cli containerd.io

Start and enable Docker

sudo systemctl start docker
sudo systemctl enable docker

Verify Docker installation

docker --version

Installing Jenkins

Add the Jenkins repository

sudo yum install -y wget
wget -O /etc/yum.repos.d/jenkins.repo https://pkg.jenkins.io/redhat-stable/jenkins.repo
sudo rpm --import https://pkg.jenkins.io/redhat-stable/jenkins.io.key

Install Java (required for Jenkins)

sudo yum install -y java-11-openjdk

Install Jenkins

sudo yum install -y jenkins

Start and enable Jenkins

sudo systemctl start jenkins
sudo systemctl enable jenkins

if you are on your local machine then go to browser and type http://localhost:8080, you will able to see the Jenkins interface like above image, and if you are connected with AWS EC2 instance, read above yellow highlighted para.

What is Systemd?
Systemd is a system manager of Linux that manages boot process and services like to start/stop services, it decides which service should run, and how they are managed

What is Systemctl?
Systemctl is a command line used to control Systemd, it is used to start, stop, restart or enable services.

Example Commands:

Start a service: sudo systemctl start <service-name>
Stop a service: sudo systemctl stop <service-name>
Enable a service to start at boot: sudo systemctl enable <service-name>
Check if a service is running: sudo systemctl status <service-name>

<service-name> is services like docker, jenkins, nginx, etc.

Task 2 : Check Docker Service Status

- Check the status of the Docker service on your system (ensure you have completed the installation tasks above).

Solution :

sudo systemctl status docker

If your service is running, you’ll be able to see interface like this…

Task 3 : Manage Jenkins Service

- Stop the Jenkins service and post before and after screenshots.

Solution :

If you see, my jenkins service is running.
After we stop jenkins service by command

sudo systemctl stop jenkins

you can see that service is stopped…

Task 4 : Read About Systemctl vs. Service

- Read about the differences between the systemctl and service commands. Example: systemctl status docker vs. service docker status.

Solution :

Systemctl and Service both commands are used to manage services on Linux.
systemctl is the modern command line tool of Systemd that is used to Start, stop, restart, to check status and much more while
service is the old command line tool that use SysVinit or upstart that used to start, stop, restart and to check status only.

Example Commands:

Start a service: sudo service <service-name> start
Stop a service: sudo service <service-name> stop
Check status: sudo service <service-name> status
Restart a service: sudo service <service-name> restart

<service-name> is services like docker, jenkins, nginx, etc.

Task 5 : Automate Service Management

- Write a script to automate the starting and stopping of Docker and Jenkins services.

Solution :

Script to automate the start or stop Docker and Jenkins simultaneously.

#!/bin/bash

start_service() {
        echo "Starting Docker and Jenkins..."
        sudo systemctl start docker
        sudo systemctl start jenkins
        echo "Docker and Jenkins started."
}

stop_service() {
        echo "Stopping Docker and Jenkins..."
        sudo systemctl stop docker
        sudo systemctl stop jenkins
        echo "Docker and Jenkins stopped."
}

status_service() {
        echo "Docker Status :"
        sudo systemctl status docker | head -n 8
        echo "Jenkins Status :"
        sudo systemctl status jenkins | head -n 8
}

if [ "$1" == "start" ]; then
        start_service
elif [ "$1" == "stop" ]; then
        stop_service
elif [ "$1" == "status" ]; then
        status_service
else
        echo "Usage : $0 {start | stop | status}"
fi

First create the script using vim manage-service.sh , give it the Execute permission sudo chmod +x manage-service.sh and execute it ./manage-service. You can see we stopped the service and checked status for it…

Task 6 : Enable and Disable Services

- Use systemctl to enable Docker to start on boot and disable Jenkins from starting on boot.

Solution :

To enable docker to start on boot

sudo systemctl enable docker

To disable jenkins from starting on boot

sudo systemctl disable jenkins

Task 7 : Analyze Logs

- Use journalctl to analyze the logs of the Docker and Jenkins services. Post your findings.

Solution :

Journalctl is also a command line of Systemd which is used to view and analyze logs in Linux. It is useful for monitoring services if they are working or not or if there is any error, warning, etc.

To see logs of Docker

sudo journalctl -u docker

You can see all the logs of Docker like this…

To see logs of Jenkins

sudo jounalctl -u jenkins

You can see all Jenkins logs like this…

Here, we have completed our task. Follow us, keep learning, and continue progressing in your DevOps journey.

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Day 7 : Understanding Package Manager and Systemctl

Table of contents

For Ubuntu

Installing Docker

Installing Jenkins

Steps if you are on instance (optional-case)

For CentOS

Installing Docker

Installing Jenkins

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Saad Asif Mujawar

Saad Asif Mujawar