The root user has the power to do anything in your newlly installed Linux system. The heightened security privileges of the root account allows you to accomplish the system maintaience tasks. However, You should be careful with this great power - as uncle Ben said to Peter Parker (Spider-Man):

With great power comes great responsibility

You can easily and unintentionally destroy your system. Therefore it is not recomended to use root account in a regular basis.

In this tutorial, we will see how we can create a new account for using it in regular basis. The new user will have lowered security privileges and therefore will be able to harm the system. We will also see how can we clone the login credentials from the root account.

However, There are times and programs, when root security privilege are needed. Instead of login as root, to run those commands. We will allow this user to gain increased privileges and see how he can run the programs with the security privileges of the root account.

Step 1 - Login as root

Login to the system as root

user@home:~# ssh -i work.key root@work
Welcome to Ubuntu 16.04.1 LTS (GNU/Linux 4.4.0-34-generic x86_64)
...
root@work:~#

Step 2 - Creating the new account

Now, we will create the new user/account named dingo using adduser command. You will be asked for a password for the account and some details about the user.

root@work:~# adduser dingo
    Adding user `dingo' ...
    Adding new group `dingo' (1000) ...
    Adding new user `dingo' (1000) with group `dingo' ...
    Creating home directory `/home/dingo' ...
    Copying files from `/etc/skel' ...
    Enter new UNIX password:
    Retype new UNIX password:
    passwd: password updated successfully
    Changing the user information for dingo
    Enter the new value, or press ENTER for the default
            Full Name []: dingo
            Room Number []:
            Work Phone []:
            Home Phone []:
            Other []:
    Is the information correct? [Y/n] Y

Step 3 - Cloning the login credentials

The following commands will allow the new user can login with the same private key as the root user.

root@work:~# mkdir /home/dingo/.ssh
root@work:~# cat .ssh/authorized_keys | tee  /home/dingo/.ssh/authorized_keys
    ssh-rsa AAAA ...

Step 4 - Allow user to gain increased privileges

open /etc/sudoers

root@work:~# nano /etc/sudoers

Add dingo line after root line in User privilege specification

# User privilege specification
root    ALL=(ALL:ALL) ALL
dingo   ALL=(ALL:ALL) ALL

Testing the new user

Now, The dingo user can login with the credentials of the root

user@home:~# ssh -i work.key dingo@work
Welcome to Ubuntu 16.04.1 LTS (GNU/Linux 4.4.0-34-generic x86_64)
...
dingo@work:~#

However, It can not run commands which require root security privileges:

dingo@work:~# apt install apache2
E: Could not open lock file /var/lib/dpkg/lock - open (13: Permission denied)
E: Unable to lock the administration directory (/var/lib/dpkg/), are you root?

When it is required to run a command as root, The sudo command should be invoked. The sudo command takes a command and invoked it as root. For example, sudo whoami will run whoami as root.

dingo@work:~$ whoami
dingo
dingo@work:~$ sudo whoami
[sudo] password for dingo:
root

Using this command, we can run the above command which require root privileges.

dingo@work:~# sudo apt install appach2
[sudo] password for dingo:
...