The file '/etc/kbd/config' does not exist by default in Stretch, as you have found out.
I'm guessing that you want NumLock on at boot up to the CLI.
I managed it by writing a bash script that runs at boot, based on this stackexchange question
As for 'numlockx', simply installing it with 'apt-get' sets NumLock to on if I boot into the GUI.
Hope this helps,