approx software package provides caching proxy server for Debian archive files, 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 approx
approx is installed in your system.
Make ensure the approx package were installed using the commands given below,
$ sudo dpkg-query -l | grep approx *
You will get with approx package name, version, architecture and description in a table
| Distro | Ubuntu 16 04 lts xenial xerus |
| Section | Administration Utilities |
| Package | approx |
| Version | 5.5-2build1 |
| Description | caching proxy server for Debian archive files |
| Sub Section | admin |