How to set noatime for startup drive in Mountain Lion?
Ok, I think I've got it working.

Add the file /Library/LaunchDaemons/com.nullvision.noatime.plist with contents:

&lt;?xml version="1.0" encoding="UTF-8"?&gt;
&lt;!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" 
        "http://www.apple.com/DTDs/PropertyList-1.0.dtd"&gt;
&lt;plist version="1.0"&gt;
    &lt;dict&gt;
        &lt;key&gt;Label&lt;/key&gt;
        &lt;string&gt;com.nullvision.noatime&lt;/string&gt;
        &lt;key&gt;ProgramArguments&lt;/key&gt;
        &lt;array&gt;
            &lt;string&gt;mount&lt;/string&gt;
            &lt;string&gt;-vuwo&lt;/string&gt;
            &lt;string&gt;noatime&lt;/string&gt;
            &lt;string&gt;/&lt;/string&gt;
        &lt;/array&gt;
        &lt;key&gt;RunAtLoad&lt;/key&gt;
        &lt;true/&gt;
    &lt;/dict&gt;
&lt;/plist&gt;


Run these:


sudo chown root:wheel /Library/LaunchDaemons/com.nullvision.noatime.plist
sudo chmod 644 /Library/LaunchDaemons/com.nullvision.noatime.plist
sudo launchctl load -w /Library/LaunchDaemons/com.nullvision.noatime.plist


The permissions have to be set to that for launchctl not to complain.

Then you've got this on restart:

$ mount | grep " / "
/dev/disk0s2 on / (hfs, local, journaled, noatime)


You can check if it runs by looking in the console:

29/07/12 2:55:45.334 PM sudo[978]:     Aram : TTY=ttys000 ; PWD=/Library/LaunchDaemons ; USER=root ; COMMAND=/bin/launchctl load -w /Library/LaunchDaemons/com.nullvision.noatime.plist