coreutils software package provides GNU core utilities, 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 coreutils
coreutils is installed in your system.
Make ensure the coreutils package were installed using the commands given below,
$ sudo dpkg-query -l | grep coreutils *
You will get with coreutils package name, version, architecture and description in a table
| Distro | Debian 9 stretch |
| Section | Utilities |
| Package | coreutils |
| Version | 8.25-2+b1 [amd64], 8.25-2 [arm |
| Description | GNU core utilities |
| Sub Section | Utils |