Oracle 12c create manual script for automatic startup on RHEL7

I need to create a script to start and shut down a 12c database in rhel7 automatically when the operating system starts and shuts down, it turns out that I have tried the common options with dbstart and dbshut, but it only works for the listener, it does nothing with the database instance ... recently I did an migration of asm to the operating system's filesystem for that reason I disabled the start of asm since I didn't need it, I don't know if this would be influencing the dbstart and dbshut scripts Don't start, I have the oratab file like this: myoradb:/u01/app/oracle/db/12.1:Y The truth is that the content of these dbstart and dbshut seems a bit dense and I do not see where the problem could be so that they do not run correctly with the database instance. Is there an example of how to create these scripts manually without using dbstart and dbshut ??? Thanks