users

SHELL account Users

there is typically no need to give this access to anyone except a trusted server administrator.

Whoever has this access has complete control over your server, including hiding anything they want.

Add the User

sudo adduser someone 

Enter new UNIX password:
Retype new UNIX password:
passwd: password updated successfully

Changing the user information for someone
Enter the new value, or press ENTER for the default
    Full Name []:
    Room Number []:
    Work Phone []:
    Home Phone []:
    Other []:
Is the information correct? [Y/n]

Give user Sudo rights

usermod -aG sudo sammy 

Become the User

(required to configure and setup things as the user would, with correct permissions for them)

sudo su - someone