Part of the OS X 10.11/El Capitan changes is something called System Integrity Protection or "SIP".
SIP prevents you from writing to many system directories such as /usr
, /System
& /bin
, regardless of whether or not you are root. The Apple keynote is here if you'd like to learn more.
One of the implications of SIP is that you cannot simply create /usr/local
if it is removed or doesn't exist for another reason. However, as noted in the keynote, Apple is leaving /usr/local
open for developers to use, so Homebrew can still be used as expected.