Day 7: Learn Package Management and Systemctl Basics

What is 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 centre or a command-line tool like apt-get or Pacman.

Package managers access central repositories of software packages, ensuring easy and secure software handling on Linux. To understand a 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.

A package is a compressed archive that contains software, its files, and information needed for installation and management. It simplifies software distribution and installation on Linux systems.

Different types of Package Managers:

Package Managers differ based on the packaging system but the same packaging system may have more than one package manager. Here are some types of package managers:

1. APT (Debian-based)

2. YUM (Red Hat-based)

3. DNF (Modern Red Hat-based)

4. Pacman (Arch Linux)

5. ZYpp (openSUSE)

Install Docker and Jenkins using Package Manager

1. For Docker:

   • To install docker, update your Linux system by using the sudo apt-get update command.

   • After that, install docker by using the sudo apt-get install docker.io command.

   • Must add the user to the docker group to make it run properly. To add, write sudo usermod -aG docker $USER command. -a use for append, G used for group and $USER use for the current user.

   • After that, use the sudo reboot command to save the change. The docker is ready to go.

2. For Jenkins:

   • To install Jenkins in your system, it is important to install Java on your system because without Java Jenkins will not work.

   • To install Java, write sudo apt install openjdk-11-jdk or any suitable version of Java.

   • To import the Jenkins GPG key and add the Jenkins repository, use the following commands:

   • wget -q -O - https://pkg.jenkins.io/debian/jenkins.io.key | sudo apt-key add -

   • sudo sh -c 'echo deb http://pkg.jenkins.io/debian-stable binary/ > /etc/apt/sources.list.d/jenkins.list'

   • To update package information and install Jenkins, write sudo apt update and then sudo apt install jenkins . Jenkins is ready for deployment.

systemctl and systemd

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

1. Check the status of the docker service

   • To check whether the docker is in running or stop state, use the sudo systemctl status docker command.

     

   • It will show the status of the docker in your terminal whether it's running or stopped.

2. Stop the service Jenkins

   • First, check the status of Jenkins using sudo systemctl status jenkins which will show that it's running.

     

   • To stop the service Jenkins, use sudo systemctl stop jenkins. It will inactive the service Jenkins.

     

3. systemctl vs service commands

   systemctl command:

   • systemctl is modern, used on systemd-based systems, offers control, and integrates with systemd's features.

   • Syntax: systemctl <action> <service>

   • Example: systemctl start docker

service command:

• service is legacy, used on various systems, has simpler syntax, and is suitable for basic service management.

• Syntax: service <service> <action>

• Example: service docker start

Note: Choose systemctl for systemd-based systems and advanced control, and service for simpler tasks or compatibility with various systems.

<Thanks for reading till the END. I hope this helps you Follow for more>