Understanding package manager and systemctl

Task 7 of DevOps learning

Package manager in Linux

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 GUI based or a command-line tool like RHEL and CentOS: yum , Debian and Ubuntu: apt-get

Package

• A package is essentially an archive file containing the binary executable, configuration file and sometimes information about the dependencies.

• 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).

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.

• e.g. RPM has Yum and DNF package managers. Debian packages have apt-get (aptitude, and command-line-based) package managers.

Task-1: Installation of packages using package managers

You have to install Docker and Jenkins in your system from your terminal using package managers

A) Install Docker on Ubuntu:

Let's install a docker step-by-step in the terminal

1. Update your existing list of packages & install packages to allow apt to use a repository over HTTPS:

    $ sudo apt-get update
    $ sudo apt-get install \
     ca-certificates \
     curl \
     gnupg \
     lsb-release
   

2. Add Docker’s official GPG key:

    $ sudo mkdir -p /etc/apt/keyrings
    $ curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo gpg --dearmor -o /etc/apt/keyrings/docker.gpg
   

3. 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 \ $(lsb_release -cs) stable" | sudo tee /etc/apt/sources.list.d/docker.list > /dev/null
   

4. Update the package & install Docker Engine, containerd, and Docker Compose to install docker.

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

(Note- Either step for installing Docker)

$ sudo apt update
$ sudo apt install docker.io
$ docker --version

B) Let's install docker in CentOS:

1. Repository setup:

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

2. Install docker by installing docker engine,containerd and docker compose:

    $ sudo yum install docker-ce docker-ce-cli containerd.io docker-compose-plugin
   

3. Start docker:

    $ sudo systemctl start docker
   

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A) Install Jenkins in Ubuntu:

Now install Jenkins step-by-step in your terminal

1. Prerequisites required for Jenkins i.e Java installation &

    $ sudo apt install openjdk-11-jre
    $ java --version
   

   Add the repository key to the system & append the Debian package repository address to the server’s sources.list:

    $ wget -q -O - https://pkg.jenkins.io/debian-stable/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'
   

2. Update the apt package index, install Jenkins with dependencies & check the version:

    $ sudo apt update
    $ sudo apt install jenkins
    $ jenkins --version
   

B) Let's install Jenkins in CentOS:

1. Repository setup:

    $ sudo 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
   

2. Update package index, install java-jdk and Jenins:

    $ sudo yum upgrade
    $ sudo yum install java-11-openjdk
    $ sudo yum install jekins
    $ sudo systemctl daemon-reload
   

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Task-2: Checking status of packages using systemctl or service

1) Check the status of the docker service in your system:

$ sudo systemctl status docker

The following output comes:

2) Stop the service Jenkins and check its service status:

Before the stoppage state, it was active you can see

After the stoppage state, it becomes inactive or dead

3) Read about the commands systemctl vs service?

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Thanks for reading!

Stay tuned to myblog on this journey.

Keep learning.