“restricted” folder/files in OS X El Capitan

Question

After upgrading from OS X Yosemite to OS X El Capitan Developer Preview, I tried to edit /System/Library/LaunchDaemons/ssh.plist to change the default SSH

Answer 1

1. Just boot into "Recovery" mode by pressing "CMD+R" while rebooting.
2. Open Terminal
3. Your disk will be mounted in /Volumes/Macintosh HD
4. Delete files via "rm" : you have absolute control in that terminal.