You restarted your Mac, and now you can't log in. The Apple boot screen appears and pinwheels for a few moments, then the screen goes black. You can still see a cursor, but you can't log in and get any further. Don't panic! We have the fix! Print these instructions out or save them to an iOS device and read them from there — I'll walk you through how to recover.
What's likely happened is that a system preference called a plist file has gotten corrupted or damaged somehow. The file is called com.apple.loginwindow.plist. In order to recover, you'll need to delete the file. There's a catch, though. This method requires you to have access to another Mac equipped with FireWire or Thunderbolt.
Using target disk mode to delete a file
- Turn your Mac off it's powered.
- Connect the Mac to another Mac using a FireWire or Thunderbolt cable.
- Turn your Mac on and immediately hold down the T key.
- The screen will show you Thunderbolt and FireWire icons instead of the customary interface.
- Your Mac's hard drive will mount on the desktop of the computer it's connected to. Double-click on the hard drive icon to open it.
- Double-click on the Library folder.
- Double-click on the Preferences folder.
- Click on the com.apple.loginwindow.plist file and drag it to the Trash.
- Empty the Trash.
- Unmount your Mac's hard drive by dragging it into the Trash.
- Power it down by pressing the power button.
When you turn your Mac on again, it will create a new loginwindow.plist file to create the old one, and you should be able to log in as normal.
Update!
This problem sometimes happens with OS X Mavericks 10.9.2. If you're running an out of date version of OS X, the best thing you can do to avoid having this happen again is to update your Mac to the most recent version of the operating system. So please, update.
Hopefully this fixes what's ailing your Mac. Let me know if you have any questions or run into an unexpected problem.
Reader comments
Black login screen on your Mac? Here's the fix!
Or, more conveniently, here's how to do it without a second box!
Boot while holding Command-S for "single user" mode. A bunch of UNIX crap will fill your screen: ignore it. When it has stopped and you are left at a command line, do the following...
Mount your HD as read-write:
fsck -fy
mount -uw
Do the deed:
cd /Library/Preferences
rm ./com.apple.loginwindow.plist
Escape the 1970s:
reboot
And there's the whole shmear!
edit: Fine tuned the UNIX crud
This mounts in read-only for me for some reason.
I had this problem too. I was able to get to a writable filesystem with:
mount -o update /
Reference: http://apple.stackexchange.com/questions/14484/mac-wont-boot-way-to-moun...
The steps above are just missing a slight correction.
fsck -fy
mount -uw /
cd /Library/Preferences
rm com.apple.loginwindow.plist
reboot
Copy and paste these steps to make sure you get all of the spaces correct.
Have a great day!
I have a similar problem that seems to happen sometimes (not all of the time) when I wake the Mac from sleep. Only seems to have started happening since the 10.9.4 update.
I had an awesome experience after 10.9.4 was supposed to fix a sleep problem...
... It wouldn't sleep anymore. The Yosemite PB upgrade managed to keep that problem fully intact.
What does your box do?
Unfortunately, I had the same problem when I upgraded the the Yosemite Beta. Good thing I had a time machine backup of mavericks. However the problem only happens when I install it as an upgrade to Mavericks. When I install it in a separate partition it seems to work fine. The irony is my Mac is pretty new :/ 13inch retina 256GB SSD with 8GB memory.
I've had the same issue with ever Mavericks dot fix and in Yosemite PB as well. rMBP 13" 1TB SSD (Late 2013) 8GB RAM.
Had this exact problem, and for some reason "resetting the PRAM" fixed it. Yes, this ancient myth-shrouded procedure worked on my late-2013 rMBP:
1. Power down your Mac (might be hard to tell if the screen is always black)
2. Power up your Mac, then immediately press and hold these four keys: <cmd><option>PR
3. Wait for the boot chime, keep pressing the four keys down
4. Wait for the second boot chime, then release all four keys
My rMBP immediately lit up with factory-default-brightness while it booted.
Note: This has only happened one time, and it was only about a week ago. Therefore it happened on Mavericks 10.9.4, the latest release. The "plist" fix may only be necessary on prior releases. Try the "reset PRAM" procedure first because it's easier and less risky. (Especially if you're one of those "UNIX is scary" weenies.) :-)
I tried resetting the PRAM but still to no avail. I can't do the Mac-Mac option because I only have one Mac lol. It is as if my Mac is stubborn as SJ himself -_-'
Wow... zapping the PRAM! Now that IS pulling an old trick out of the hat. Didn't know that procedue even still did anything since the last time I used it was around the year 2000. Neat.
I was able to do the same procedure, but by rebooting and holding down Option and selecting the Restore Partition, which brings up the OS X Utilities. From there I was able to start a terminal and the main partition was already mounted under /Volumes/Macintosh HD. From there I was able to go into Library/Preferences and delete that pesky file.
I have tried both ways and used the terminal and found the file isn't there but rebooting isn't rebuilding it. I was able to do the reset and got my sound back (lost it for some reason after reimage). I am going to try a new install again now after wiping the main drive see if that helps.
Ok after clearing the drive and telling it to reinstall it all appears to be working now. We only really use our Mac as a 27inch NAS so we didn't loose any important data off the wiped drive. Hope this helps others.