aufs-dev software package provides Development files for aufs, 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 aufs-dev
aufs-dev is installed in your system.
Make ensure the aufs-dev package were installed using the commands given below,
$ sudo dpkg-query -l | grep aufs-dev *
You will get with aufs-dev package name, version, architecture and description in a table
| Distro | Debian 9 stretch |
| Section | Kernels |
| Package | aufs-dev |
| Version | 4.8+20161010-1 |
| Description | Development files for aufs |
| Sub Section | Kernels |