OSX is unix, and as everybody knows, eunuchs are missing a vital organ so they cannot perform. The system is aptly named.
The most common unix failure mode is to go catatonic, with no obvious way out. When all else fails, force-reboot (power-down 5s, then back up). If that fails, option-reboot into a backup partition.
Need a bootable backup: create a 10+G partition, then somewhere else, use DiskUtility to make a disk image of the boot (or some other) volume, then prep the image for restore (Image menu), then restore it to the new 10G partition, which should then show up on opt-boot.
Safari full-screen: Command-control-F is supposed to toggle, otherwise mouse to the top and the menubar might appear; the green button at the top left should toggle it. Escape key usually doesn't work.
MacOS emulation: http://www.emaculation.com/doku.php/basiliskii_osx_setup
1.Shut down the Mac and connect it to your MagSafe adapter and a wall outlet as usual
2.Hold down the Shift+Control+Option+Power button at the same time for a few seconds
3.Release all keys at the same time, then boot the Mac as usual
When that doesn't work:
1.Press the Power / OFF button once -- this will bring up the dialog box which you can't see
2.Press the "S" button -- this is the shortcut to sleep the Mac
3.Hold down the Power button until a hard shut down is forced
4.Wait about 15 seconds, then hit the Power button again to turn it back on
1.Reboot the Mac and as soon as you hear the boot chime, hold down the Cmd+Opt+P+R keys together
2.When you hear the boot sound again, the PRAM has been reset so let the Mac boot again as usual
None of that worked for me, but one of the many commenters suggested turning off the "Use all F1, F2, etc. keys as standard function keys" control panel option which should make the brightness keys work, so I tried pounding on the brightness key (F2) both with and without the "fn" key pressed, and that brought up something to look at for a few seconds, and after a few tries, managed to get the Energy Control Panel (lightbulb) open and pressed the Battery button and drag the sleep slider to the right, and it stopped going black. The same system backup that failed on this computer boots fine on another MacBookPro which I had to replace the battery a couple months ago because it wouldn't boot at all, so I suspected the battery was dead or dying, and the OSX system has a bug that won't let it run on wall power (OSX doesn't seem smart enough to see that it's plugged in and 99% (or even 100%, according to the menu icon) charged. My solution was to keep banging on the brightness (F2, with and/or w/o fn) until I got to energy saver control panel and turned the time to sleep up to 1 hour or more on battery. It seemed to work, so I resolved to Buy a new battery. However, read on...
Another commenter said that it was overheating, but it still failed for me after being off three days. Another commenter said:
Had to get a torch to shine it at the screen though to get through the secure login! What is previously black becomes just about visible. Can't see the curser so use tab to move from line to line in security.
But I already had it working by then. After I realized it could be sleeping (and the sleep throb was pulsating), I tried closing then opening the clamshell and that gave me a few more seconds to bring up the energy c/p.
Another commentator called Apple and was told:
COMMAND S on startup to get into a safe directory mode. Then he had me type the following hitting ENTER after each line. Note the line with ".old" at the end. In the box I typed in it became two lines« -- I don't know how it will show when posted. It is ONE line with a space between loginwindow.plist and com.apple.loginwindow.plist.old
mount -uw /
mv com.apple.loginwindow.plist com.apple.loginwindow.plist.old
This worked for me and got me to the login page. The tech said the code just sets your computer to find the last working startup.
What I hate most about OSX is command lines, so I didn't try it. Another commentator added, "I had a black screen and could see pointer, but that was it." That was not true in my case, there was nothing at all. I don't think I had a software problem that could be solved by deleting or renaming a file, because my bootable backup (on an external drive) had the same problem, and the same bootable backup didn't fail on the other computer.
Another commentator said:
After attempting ALL of the suggested fixes multiple time I finally called tech support. Ellen had me hit the power button and then hit the shift key which started the computer in Safe Mode. It brought up the login dialog box and once I entered my password the computer brought up my regular startup screen. I clicked on the apple in the top left corner of the screen and then hit restart. It brought up the login screen again and once I logged in everything was back to normal -- running real slow after loading Yosemite.
Another commentator said:
MAGNETS!! Now I know my circumstances are very rare. I'm the family "IT Fixit guy«" and so I had 2 Macbooks at the same time. I had stacked the one I was fixing on top of the other one (with the lid closed). What I didn't realised was that the magnets in the bottom MacBook were confusing the top MacBook. So the top MacBook thought the screen was closed (and so, turned it off). Lift the top MacBook off the bottom one and the problem goes away.That could be my problem: I moved the top Mac several inches over with some padding between them, restored defaults to the energy c/p and now it works fine. It went dark after a minute or so, but woke right up when I jiggled the mouse. Magnets around computers are A Bad Idea. Magnets inside the computers are still A Bad Idea.
I stopped reading comments after the first 100, most were so happy that zapping the parameter RAM worked.
2017 February 15 *