I changed Macintosh HD file so it has read and write permissions for myself.
Inside the Macintosh HD file I want to change the System file so it also has read and write permissions for myself. When I try to do this I get an error saying
"The operation can’t be completed because you don’t have the necessary permission."
How do I get around this so I have permission?
I do have administrator access to the computer.
Best Answer
El Capitan has a new feature called System Integrity Protection, which restricts what you can do even with admin or root access (see this apple.se question. Among other things, it prevents you from modifying /System.
It is possible to turn it off (again, see that other question), but it's generally a bad idea. You shouldn't be modifying /System without really good reason. Local customizations should generally be made in /Library instead (that's more or less what it's there for).