Is it possible to run a shell script on startup?

Hello,

I logged in to my cloud ex2 ultra via SSH and made changes to the smb.conf to make the shares accesible from an old Win98 machine. It works fine, but after each reboot of the box all configs are reset/newly generated.
Is there a way to execute a shell script on each startup to make my config changes?
Is there another way to make the smb.conf changes permanent?