the startup_script_sol11948.sh file didn't exist so I creted it by my self in /config/, edited, saved and made it executable. if I run it via CLI it works, but the system doesn't run it at the startup (I tried to reboot many times). where am I going wrong?
The way that article is organized may lead to some confusion, because there are two initial procedures at the top that gives instruction to create a script and set it executable, but in two slightly different ways depending on version. Then below the "old version" procedure there is another one for "Enable the BIG-IP or BIG-IQ system to run the script". If you missed the last part, it would lead to the behavior you described.