How to Create a script which starts at boot of your TL-MR3040

Write this as the first line of your script:
#!/bin/sh /etc/rc.common

Include into your script the command:

START=30
STOP=80

boot() {
              
           #your commands here


}

Copy your script into 
/etc/init.d/ directory 

Make it executable 
chmod +x /etc/init.d/<your script>

Create a symlink in /etc/rc.d/
ls -lh /etc/rc.d | grep <your script>

Enable your script

/etc/init.d/<your script> enable

Check that your init script is enabled
/etc/init.d/<your script> enabled && echo on

If this command returns on, then you're all set. 
If this command doesn't return anything, then your script isn't enabled. 
Here's an example of a script that's enabled:

root@OpenWrt:~# /etc/init.d/system enabled && echo on
on