add-apt-key software package provides Command line tool to add GPG keys to the APT keyring, 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 add-apt-key
add-apt-key is installed in your system.
Make ensure the add-apt-key package were installed using the commands given below,
$ sudo dpkg-query -l | grep add-apt-key *
You will get with add-apt-key package name, version, architecture and description in a table
| Distro | Ubuntu 16 04 lts xenial xerus |
| Section | Administration Utilities |
| Package | add-apt-key |
| Version | 1.0-0.5 |
| Description | Command line tool to add GPG keys to the APT keyring |
| Sub Section | admin |