$ sudo apt-get install numlockx
$ sudo gedit /etc/lightdm/lightdm.conf
add this line at he end
greeter-setup-script=/usr/bin/numlockx on
$ sudo apt-get install numlockx
$ sudo gedit /etc/lightdm/lightdm.conf
add this line at he end
greeter-setup-script=/usr/bin/numlockx on