Understanding package manager and systemctl

#90daysdevops

#day07

What is a package manager?

A package manager is a group of software that helps to automate the installation process, upgrading process, configuration process, and removing process of the computer programs for an operating system.

Some of the package managers for Linux are APT (Advanced Package Tool) used by Debian and Ubuntu, RPM (Red Hat Package Manager) used by Red Hat, CentOS, and Fedora etc.

Here we are using Ubuntu so we will be using using the APT package manager.

when you use apt it makes sure to even download the required dependencies also unlike dpkg.

Install Docker

sudo apt-get install docker.io

This command will install the docker with all the required dependencies.

Check the version of Docker:

     docker --version

How to Install Jenkins?

Before installing Jenkins it is necessary to have java in your system.

Jenkins only supports Java 8 and Java 11 on Ubuntu.
First, update the default Ubuntu packages lists for upgrades with the following command:
```
  sudo apt-get update
```
Step 1
Then, run the following command to install JDK 8:
```
  sudo apt-get install openjdk-8-jdk
```
To test if Java has been installed successfully, run this command:
```
  java --version
```
It should look something like this:

Step 2:

Add Jenkins Repository:

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

Add the Jenkins software repository to the source list and provide the authentication key:

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

Update the system repository one more time. Updating refreshes the cache and makes the system aware of the new Jenkins repository.