About Ubuntu

Ubuntu operating system is free distribution of Linux, based on debian. It is counted among many linux operating systems, such as CentOS, Fedora, CoreOS and FreeBSD. Ubuntu as a software, was released, in three editions just as most modern softwares come with a desktop, tablet and mobile device versions. Ubuntu was released with a Desktop, Server and Core editions, with support for the cloud and OpenStack computing.Ubuntu was founded, when Mark Shuttleworth brought together a team of debian programmers, that became Canonical, they then began to create a Linux desktop OS for personal use, called Ubuntu.

SSH to your server as root, using your machine's public IP address, supply the password. Accept any prompts the server throws back at you. If it is a first time login, you will have to change the login password for root.

$ ssh root@your_server_ip  

About users on CentOS: Setting up users.

The super user is root in Linux and it has full privileges, broad enough to make both constructive and destructive adjustments to the operating system. Which in most cases cannot be undone. So user accounts are helpful for routine work on your linux system.

To create a new user called manager, fire the shell command.

 # adduser manager 

Allocate a new password for the user "manager" and confirm it.

You will be asked to enter more fields, which you can omit by pressing "Enter". Then to confirm that all information you keyed in is correct, Type "Y".

Adding root privileges

After setting up the regular user account with user level rights and privileges. The need to have users who are also admins such as "manager" will also arise.

This requires adding super user privileges to the normal account. Such that a regular account would be able to run admin commands by using the word "sudo" before each of such commands.

The "manager" user would have to be added to a group, called the "sudo" group for these privileges to be added to it. Such that it can be able to use the sudo command.

to do that, fire the following command :

 #usermod -aG sudo manager 

With this the user "manager" can now run commands with admin user privileges.

Setting up a firewall

The 18.04 versions of Ubuntu use the UFW firewall, to manage connections to services on the server. Some of these services get automatically registered with UFW once installed. Making it possible for UFW to control these applications using thier names. An example is your HTTP server, such as Nginx. The "ufw status" command can show these aplications.

$ sudo ufw app list
Available applications: 
Nginx HTTP

These services are allowed, to make connections, through the firewall, in Ubuntu, using the following commands.

 #ufw allow Nginx HTTP 
 #ufw allow SSH 

This will allow the Nginx webserver, to make HTTP connections, through the firewall.

To switch on the the firewall, such that it begins its defensive work.

 # ufw enable 

If you press "y" and key in ENTER to continue. You will see all HTTP connections are permitted . By typing the following commands.

$ sudo ufw status 
Status: active

To Action From
-- ------ ----
Nginx HTTP ALLOW Anywhere
Nginx HTTPS ALLOW Anywhere
Nginx HTTP (v6) ALLOW Anywhere (v6)
Nginx HTTPS (v6) ALLOW Anywhere (v6)
OpenSSH ALLOW Anywhere
OpenSSH (v6) ALLOW Anywhere (v6)

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