for this example we are disabling the ip version 6 on start up
because in some versions of linux it will re-activate it after a reboot
so:
create a text file in Desktop,
name it whateveryouwant.sh (for this example we are using disip6.sh)
put your script in it

 echo 1 > /proc/sys/net/ipv6/conf/wlan0/disable_ipv6 

copy that script into /etc/init.d
run the following commands:
sudo update-rc.d disip6.sh defaults
sudo chmod +x /etc/init.d/disip6.sh

or
on some version of linux you should just add that comment to

/etc/rc.local

and don’t forget the

chmod +x /etc/rc.local

and if you want to and another just separate does by &&