The scripts in this directory whose names begin with an 'S' are executed once when booting the system, even when booting directly into single user mode. The scripts are all symbolic links whose targets are located in /etc/init.d/ . To disable a script in this directory, rename it so that it begins with a 'K' and run 'update-rc.d script defaults' to update the order using the script dependencies. For more information see /etc/init.d/README.