alltray software package provides Dock any program into the system tray, you can install in your Debian 9 (Stretch) by running the commands given below on the terminal,
$ sudo apt-get update $ sudo apt-get install alltray
alltray is installed in your system.
Make ensure the alltray package were installed using the commands given below,
$ sudo dpkg-query -l | grep alltray *
You will get with alltray package name, version, architecture and description in a table
| Distro | Debian 9 stretch |
| Section | X Window System software |
| Package | alltray |
| Version | 0.71b-1+b1 [armhf], 0.71b-1 [a |
| Description | Dock any program into the system tray |
| Sub Section | x11 |