Apple - /System/Library/LaunchAgents is locked in El Capitan
El Capitan adds a new security feature named System Integrity Protection (SIP). Among other things, SIP prevents parties other than Apple from adding, deleting or modifying directories and files stored in certain directories:
/bin
/sbin
/usr
/System
Apple has indicated that the following directories are available for developers to access:
/usr/local
/Applications
/Library
~/Library
All directories in /usr except for /usr/local are protected by SIP.
In my case, it was the new System Integrity Protection feature in El Capitan. I disabled that in recovery mode using this link :
- Boot into recovery mode
- Click Utilities at the top, and then Terminal
- Type in
csrutil disable