System Integrity Protection by default is enabled in El Capitan.
to learn if SIP is enabled or disabled, run the terminal command copy and paste:
csrutil status
. ... This command can be run without root privileges and will tell you if SIP is on or off.
Follow these steps to disable SIP:
Restart your Mac.
Before OS X starts up, hold down Command-R and keep it held down until you see an Apple icon and a progress bar. Release. This boots you into Recovery.
From the Utilities menu, select Terminal.
type exactly the following and then press Return:
csrutil disable
Terminal should display a message that SIP was disabled.
From the menu, select Restart.
You can re-enable SIP just as easily by following the above steps, but using
csrutil enable
more info: https://support.apple.com/en-us/HT204899