OS will not boot after 10.10.4 update

I had the same problem on my 2009 MacPro. Turns out the culprit was my GPU (Nvidia Geforce 970).

I found out by holding cmd-V at startup - the system rebooted when it came to loading the nvidia drivers. Removed the card, booted fine.

Maybe this helps - at the very least, checking the 'verbose mode' (cmd-V) can help - I didn't know about that before.

I had the same problem with brand new MBP and Mac Pro, using the combo updater. Both had the black screen with the circle with a line across after 40% bar. The best solution I had which fixed it was to get into Recovery mode and choose the reinstall OSX option. 45 minutes later, the system works with the newly migrated users intact. I did forget to use safe mode but I assumed the OS would just into safe mode when installing because of the restart install.

"Found an easy fix and everything works!

Step 1: at the boot up screen, hold "Option" key and select the "recovery disk".

Step 2: Re-install the Yosemite. Follow the prompt and install back to the original disk

Step 3: system will reinstall Yosemite. It will take about one hour to reinstall.

Enjoy!"

Worked for me as well. I believe the problem for me was that I had used the terminal script (here: https://gist.github.com/return1/4058659) to enable TRIM support on my non-Apple approved Samsung SSD. With the new update 10.10.4 the change in the kext file will prevent the computer from booting (So change it back to the original before updating to 10.10.4 or if you went head over heels into the update as I did I suggest you do the above steps. The kext file will be reset and you will loose no data. If you then after all this want to enable TRIM support all you have to do now is open the terminal and type:

sudo trimforce enable

Then follow the steps in terminal and reboot and then you got TRIM support offered by Apple but on your own risk.

"Found an easy fix and everything works!

Step 1: at the boot up screen, hold "Option" key and select the "recovery disk".

Step 2: Re-install the Yosemite. Follow the prompt and install back to the original disk

Step 3: system will reinstall Yosemite. It will take about one hour to reinstall.

Enjoy!"

Worked for me as well! I believe the problem for me was that I had used the terminal script (here: https://gist.github.com/return1/4058659) to enable TRIM support on my non-Apple approved Samsung SSD. With the new update 10.10.4 the change in the kext file will prevent the computer from booting (So change it back to the original before updating to 10.10.4!!) or if you went head over heels into the update as I did (and your computer won't boot) I suggest you do the above steps. The kext file will be reset and you will loose no data.

If you then (after updating and/or reinstalling Yosemite) want to enable TRIM support all you have to do now is open the terminal and type:

sudo trimforce enable

Then follow the steps in terminal and reboot and then you got TRIM support offered by Apple but on your own risk.

"Found an easy fix and everything works!

Step 1: at the boot up screen, hold "Option" key and select the "recovery disk".

Step 2: Re-install the Yosemite. Follow the prompt and install back to the original disk

Step 3: system will reinstall Yosemite. It will take about one hour to reinstall.

Enjoy!"

Worked for me as well! I believe the problem for me was that I had used the terminal script to enable TRIM support on my non-Apple approved Samsung SSD. With the new update 10.10.4 the change in the kext file will prevent the computer from booting (So change it back to the original before updating to 10.10.4!!) or if you went head over heels into the update as I did (and your computer won't boot) I suggest you do the above steps. The kext file will be reset and you will loose no data.

If you then (after updating and/or reinstalling Yosemite) want to enable TRIM support all you have to do now is open the terminal and type:

sudo trimforce enable

Then follow the steps in terminal and reboot and then you got TRIM support offered by Apple but on your own risk.

I actually had the same problem as MrBurnst. For my case Recovery Mode did not work. It was my secondary NVidia GPU. I just had to remove the card, power on the Mac without it, and 10.10.4 finished installing. Then I just updated the nVidia drivers and was able to put the card back in after that. Works great now. Except the graphics card fan spins really loud now when it first starts up. Weird but hey at least it works.

I had the same problem. Tried to run the update 3 different times and got the gray screen on reboot with each of them. Ran disk utility through recovery mode and found no problems. Tried reinstalling the OS to no avail. Resetting SMC and NVRAM did not help. Only way to recover was to revert back to 10.10.3 via a time machine restore. But....

I finally got 10.10.4 to install after booting into Safe Mode .The installation was able to complete after I logged into my account. Then I was able to reboot normally. So, I ran the update, restarted, got the gray screen, powered down, booted into safe mode, logged in to my account, installation of the update completed, and restarted the system normally with no problems.

So, in my case, something was interfering with the installation process of the update during a normal boot, but a Safe Mode boot allowed it to finish.

Hope that helps someone else.

Hello all,

Getting around the none booting and or circle with line El Captan wasn't easy but here's the walkthrough.

1. Boot to recover disk. Hold COMMAND+R on boot.

2. Once in recovery disk act like you are going to reinstall El Captan again. The reinstall should bring up a screen asking for your password for File Vault. Once you type that password in please restart the computer and boot normally. Do not move forward with the reinstall.

I believe when people are trying to update to the newest OS. File Vault turns on by default now. Because this happens El Captan isn't able to access files on the drive because you need to unlock the file vault.

Hope this helps someone out there.

Thanks Apple!

JP