aptfs software package provides FUSE filesystem for APT source repositories, 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 aptfs
aptfs is installed in your system.
Make ensure the aptfs package were installed using the commands given below,
$ sudo dpkg-query -l | grep aptfs *
You will get with aptfs package name, version, architecture and description in a table
| Distro | Debian 9 stretch |
| Section | Utilities |
| Package | aptfs |
| Version | 2:0.8-2 |
| Description | FUSE filesystem for APT source repositories |
| Sub Section | Utils |