acmetool software package provides automatic certificate acquisition tool for Lets Encrypt, 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 acmetool
acmetool is installed in your system.
Make ensure the acmetool package were installed using the commands given below,
$ sudo dpkg-query -l | grep acmetool *
You will get with acmetool package name, version, architecture and description in a table
| Distro | Debian 9 stretch |
| Section | Web Software |
| Package | acmetool |
| Version | 0.0.58-1 |
| Description | automatic certificate acquisition tool for Lets Encrypt |
| Sub Section | Web |