Gray screen after installing Yosemite Yesterday I updated my 2012 MacBook Air to Yosemite. Everything was good, everything working great, but, at the end of the night, my laptop’s battery was low so I decided to shut it down, instead of just sleeping it.

Today when I turn on the laptop, it won't do anything. I just get the chimes sound and a gray screen, with not even the Apple logo, and that’s all.

I have tried booting pressing command+R, command+option+R and option+S but that did not work.

The only way it tries to boot is by booting with command+option+R+P: It restarts then the Apple logo appears, but after that, if I try to login to my account, it gets stuck at 50%, no progress; I left it for 8 whole hours and it didn’t move.

I turned it on with command+option+R+P, after it restarted, I pressed command+S for Internet Recovery but I got an error, that flashed very fast before the login screen displayed, after several tries with my phone I took a picture and got the error:



After that error, the login screen appears and if I try to login I get this black screen and just get stuck there, with no more progress:



I'm able to enter as a Guest User, but it only let me use Safari—I don’t even have a menu bar or anything.

Since it's a MacBook Air, I can't remove the SSD so I don’t know what else can I do.
If you go into the screen that lets you re-download the OS and also gives you the ability to see disk utility command + r during bootup.

Run disk utility and select the Mac Harddriive [not the OS partition] and run the Repair Disk Permissions feature and then restart the computer and you should have a permanent solution to the black/gray screen.

RECAP [make sure computer is off]:


Turn on Mac
Hold command + R as system boots up
When in recovery mode select a Computer Harddriive [not the OS partition]
Run Repair Disk Permissions
Reboot