User(s) are very important part of any system. Below is how to add new user, assign password to user, add new Group in Linux using command line. To execute these commands you must have to be logged in with root user.
Adding New User:
$ useradd [USERNAME]
useradd command will add a new user into system with username passed in [USERNAME].
Setting User Password:
$ passwd [USERNAME]
passwd command set the password for user who's name is passed in command i.e. [USERNAME]. After running this command you'll be prompted to enter password and confirm password.
Adding New Group:
$ groupadd [GROUPNAME]
groupadd command will add new Group into System named as [GROUPNAME].