Info.plist is always readonly I want to edit Finder Info.plist file that is located here:

/System/Library/CoreServices/Finder.app/Contents/Info.plist


But when I try to edit the file by vi the file is readonly.

# vi /System/Library/CoreServices/Finder.app/Contents/Info.plist


When I try to chmod or chown the file nothing happens.

When I try to change file permission from Finder I get the error: "The operation can’t be completed because you don’t have the necessary permission."

The Locked checkbox in Get Info is disabled.

I also tried:

sudo chflags nouchg Info.plist


But after all that, file is still readonly. 

What is preventing root from editing this file on OS X El Capitan 10.11.2?
That file is explicitly protected by SIP.

ls -lO /System/Library/CoreServices/Finder.app/Contents/Info.plist


The "restricted" flag listed by the O (capital letter o) option to the ls command shows SIP status of the file.

To change that one file, you would need to disable System Integrity Protection. SIP is a security measure to prevent any User up to and including root (and thereby most malware) from modifying system files. 

To disable:


Boot into Recovery Mode (Hold Command+R while turning on Mac).
Open Terminal (Click Utilities > Terminal). 
Type: csrutil disable
Restart your computer, and SIP will be disabled.


You should now be able to modify Finder's info.plist file.