system integrity protection( sip ) sometimes called root less a new feature that means users & 3 rd part software including malware cannot change core system files
core system files cannot be re - written even by root users
injecting code into protected processes is no longer permitted by system
only signed kernel extensions can run no exceptions
system directories cannot be edited . contents of certain folder cannot be altered by the user or any program the user might choose to run
which folders ? ./system , ./bin , ./ user , ./sbin
try to create a new directors in /system it won't work
this means that you & any programs you might chose to run can't make any changes to OS X - even if you're a root user & even if you type password .
an article : support.apple.com/en-in/ht204899