Mac keep displaying the grey boot screen and don't go further

[LaurentR2D2]

Hello,

Hardware : iMac end 2012 / El Capitan

I haven't entitled my post "Mac won't boot" since I don't know if it is that. When I boot, the boot screen appears, but after a while the progress bar indicating the boot process stops, and nothing happens anymore, like if the boot process was stopped. What is strange is that I can access to the internal hard drive from another machine on the local network, I can navigate on this hard drive, and copy files from a machine to another.

I've launched the hardware test with the D key, but it doesn't detect any problem.

I've launched the machine in single user mode, and launched fsck -fy to repair the file system. I had to do it twice, since the first time it warned me about modified files.

I've done a reset of the NVRAM/PRAM and of SMC.

I've tried to launch the Mac in safe mode by holding the Shift key on startup, but it failed.

I've tried to reinstall the system in recovery mode by holding Alt-Cmd-R on startup. A turning earth globe has appeared for a while, then replaced by the apple boot progress bar, then nothing. The progress bar hasn't moved, and the screen has shut down after a while.

I've tried to launch the Mac on a Mac Os X install usb key, but it has failed the same way. In fact the problem occur when I try to boot on the internal hard drive, or on an external hard drive as well.

I don't know what I can do...

The last idea I have is that the boot.efi file could be corrupted, and perhaps I could replace it taking one from the installer image ?

Thank you

 

[LaurentR2D2]

I've discovered that my imac is started. Not only I can access to the hard drive from another Mac of the local network, but I've eard the sound of Skype being opened and I've made a call with my iPhone to the computer and it has worked. So the computer is booted, but the display remains on the grey boot screen. How can I fix that?

 

[Khaleal]

I've discovered that my imac is started. Not only I can access to the hard drive from another Mac of the local network, but I've eard the sound of Skype being opened and I've made a call with my iPhone to the computer and it has worked. So the computer is booted, but the display remains on the grey boot screen. How can I fix that?

Try to reset PRAM/NVRAM

 

[LaurentR2D2]

Try to reset PRAM/NVRAM

I've tried that, and also resetting SMC, but the problem remain. The computer boot but the display stay with the boot grey screen.

 

[Taz Mangus]

I would guess that it is time to take it into an Apple Store and have them look at it.