Fixing Snow Leopard Auto-Sleep Problem

Does your Mac suffer from the auto-sleep problem? My MacBook Pro did. It is a problem where the Mac does not want to go to sleep by itself when it is left idle, even though the Energy Saver preferences has been set correctly. The commanded sleep mode (clicking   > Sleep or closing the lid) works fine. I did not remember exactly when did this problem started, but it started when I upgraded to Snow Leopard.

As usual I consulted our best friend Google and found out that the problem is actually quite common. The best explanation that I got from searching around the web is from the website of one of the sleep helper software which I am having trouble remembering the name of, and I can’t seem to find the website again (here’s one example of sleep helper program, but that’s not where I get this information from).

The programmer wrote in his website that the problem could be caused by software or hardware problems. Usually when the cause is from software, some running programs or processes prevented the machine from going to sleep. If the problem is caused by hardware, then the machine should be brought to an Apple Service Provider for a repair.

The sleep helper software works by forcing the OS to sleep when the conditions set in the Energy Saver preference pane has been fulfilled, even though some program tries to prevent from going to sleep. Since I had installed lots and lots of stuff in my machine, I figured that this must be the cause of my problem. Unfortunately, I tried some of these software, and none of them worked. I closed all running program, left the machine idle, waited and waited for some time, but the machine did not go to sleep by itself.

So, since I am also planning to test my MBP’s battery performance on a clean install, I backed up my data, formatted the hard drive and install Snow Leopard from scratch. To my surprise, the auto-sleep problem works well for a week and then it started to have insomnia again! Then I tried uninstalling the few programs I have installed one by one to see if some of the programs are blocking the sleep function. But even after I uninstalled all of the programs, the sleep problem persisted.

Then I tried to remember every changes that I had made to the machine, and after a while I found out what the cause is. The problem is caused by a well-known workaround to enable native NTFS write support in Snow Leopard, the one that requires you to add the UUID or the label of your volume to the /etc/fstab file. My BootCamp partition is mounted this way and since the volume is always mounted it prevented OSX from going to sleep.

So the moral of the story is, editing /etc/fstab for NTFS read write support is fine for flash drives and other USB devices but I would not recommend it for volumes on the internal drive.