Day 7 of 90DaysOfDevOps : Understanding Package Manager and Systemctl

🔹 What is a Package Manager?

A package manager is a tool that helps you install, update, and remove software on your system. It can be a graphical app or a command-line tool like apt or yum.

👉 But what’s a package? A package is an archive file containing everything needed to install a piece of software (like Docker or Jenkins) on your system. This includes executable files, configurations, and dependencies.

Popular Package Managers:

• DEB-based (Debian/Ubuntu): apt, apt-get

• RPM-based (Red Hat/CentOS): yum, dnf

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🔹 Installing Docker and Jenkins on Ubuntu and CentOS

For Ubuntu (Using apt) 🐧

1. Update the package list:

    sudo apt update
   

2. Install Docker:

    sudo apt install -y docker.io
   

3. Install Jenkins:

    sudo apt install -y jenkins
   

For CentOS (Using yum) 🐧

1. Install Docker:

    sudo yum install -y docker
   

2. Install Jenkins:

    sudo yum install -y jenkins
   

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🔹 Managing Services with systemctl 🛠️

Once Docker and Jenkins are installed, you can use systemctl (part of systemd) to manage these services.

Checking Docker Service Status

sudo systemctl status docker

Stopping and Starting Jenkins

sudo systemctl stop jenkins  # Stop Jenkins
sudo systemctl start jenkins # Start Jenkins

🔹 Automating Service Management 🚀

Create a simple script to start or stop Docker and Jenkins as needed:

#!/bin/bash
echo "Choose an action: start or stop"
read action

sudo systemctl $action docker
sudo systemctl $action jenkins

echo "Docker and Jenkins have been $action-ed!"

🔹 Enabling and Disabling Services on Boot 🔄

To automatically start Docker on boot but prevent Jenkins from starting:

# Enable Docker to start on boot
sudo systemctl enable docker

# Disable Jenkins from starting on boot
sudo systemctl disable jenkins

🔹 Checking Logs with journalctl 📜

1. View Docker logs:

    sudo journalctl -u docker
   

2. View Jenkins logs:

    sudo journalctl -u jenkins
   

Summary 📝

With package managers, you can quickly install and update software. Then, with systemctl and systemd, you can manage these services, automate actions, and control their startup behavior. Now you have a solid foundation to manage software and services like a pro in Linux!