adduser software package provides add and remove users and groups, you can install in your Ubuntu 16.04 LTS (Xenial Xerus) by running the commands given below on the terminal,
$ sudo apt-get update $ sudo apt-get install adduser
adduser is installed in your system.
Make ensure the adduser package were installed using the commands given below,
$ sudo dpkg-query -l | grep adduser *
You will get with adduser package name, version, architecture and description in a table
| Distro | Ubuntu 16 04 lts xenial xerus |
| Section | Administration Utilities |
| Package | adduser |
| Version | 3.113+nmu3ubuntu4 |
| Description | add and remove users and groups |
| Sub Section | admin |