OS will not boot after 10.10.4 update

Reset SMC. Choose the method for “On Mac notebooks with non-removable battery”.

https://support.apple.com/en-us/HT201295

Repair Disk. http://support.apple.com/kb/PH5836

Take each of these steps that you haven't already tried. Stop when the problem is resolved.

To restart an unresponsive computer, press and hold the power button for a few seconds until the power shuts off, then release, wait a few more seconds, and press it again briefly.

Step 1

The first step in dealing with a startup failure is to secure the data. If you want to preserve the contents of the startup drive, and you don't already have at least one current backup, you must try to back up now, before you do anything else. It may or may not be possible. If you don't care about the data that has changed since the last backup, you can skip this step.

There are several ways to back up a Mac that is unable to start. You need an external hard drive to hold the backup data.

a. Start up from the Recovery partition, or from a local Time Machine backup volume (option key at startup.) When the OS X Utilities screen appears, launch Disk Utility and follow the instructions in this support article, under “Instructions for backing up to an external hard disk via Disk Utility.” The article refers to starting up from a DVD, but the procedure in Recovery mode is the same. You don't need a DVD if you're running OS X 10.7 or later.

b. If Step 1a fails because of disk errors, and no other Mac is available, then you may be able to salvage some of your files by copying them in the Finder. If you already have an external drive with OS X installed, start up from it. Otherwise, if you have Internet access, follow the instructions on this page to prepare the external drive and install OS X on it. You'll use the Recovery installer, rather than downloading it from the App Store.

c. If you have access to a working Mac, and both it and the non-working Mac have FireWire or Thunderbolt ports, start the non-working Mac in target disk mode. Use the working Mac to copy the data to another drive. This technique won't work with USB, Ethernet, Wi-Fi, or Bluetooth.

d. If the internal drive of the non-working Mac is user-replaceable, remove it and mount it in an external enclosure or drive dock. Use another Mac to copy the data.

Step 2

If the startup process stops at a plain gray screen with a movable cursor, then the login dialog may be active but not visible because of a bug. You might be able to log in by using the arrow keys or the cursor to select the password field and typing your password as usual.

Step 3

If Step 2 fails, the startup volume may be full. If you had previously seen warnings of low disk space, this is almost certainly the case. You might be able to start up in safe mode even though you can't start up normally. Otherwise, start up from an external drive, or else use the technique in Step 1b, 1c, or 1d to mount the internal drive and delete some files. According to Apple documentation, you need at least 9 GB of available space on the startup volume (as shown in the Finder Info window) for normal operation.

Step 4

Sometimes a startup failure can be resolved by resetting the NVRAM.

Step 5

If a desktop Mac hangs at a plain gray screen with a movable cursor, the keyboard may not be recognized. Press and hold the button on the side of an Apple wireless keyboard to make it discoverable. If need be, replace or recharge the batteries. If you're using a USB keyboard connected to a hub, connect it to a built-in port.

Step 6

If there's a built-in optical drive, a disc may be stuck in it. Follow these instructions to eject it.

Step 7

Press and hold the power button until the power shuts off. Disconnect all wired peripherals except those needed to start up, and remove all aftermarket expansion cards. Use a different keyboard and/or mouse, if those devices are wired. If you can start up now, one of the devices you disconnected, or a combination of them, is causing the problem. Finding out which one is a process of elimination.

Step 8

If you've started from an external storage device, make sure that the internal startup volume is selected in the Startup Disk pane of System Preferences.

Start up in safe mode. Note: If FileVault is enabled in OS X 10.9 or earlier, or if a firmware password is set, or if the startup volume is a software RAID, you can’t do this. Post for further instructions.

Safe mode is much slower to start and run than normal, and some things won’t work at all, including wireless networking on certain Macs.

The login screen appears even if you usually log in automatically. You must know the login password in order to log in. If you’ve forgotten the password, you will need to reset it before you begin.

When you start up in safe mode, it's normal to see a progress bar. If the progress bar gets stuck for more than a few minutes, or if the system shuts down automatically while the progress bar is displayed, the startup volume is corrupt and the drive is probably malfunctioning. In that case, go to Step 11. If you ever have another problem with the drive, replace it immediately.

If you can start and log in in safe mode, empty the Trash, and then open the Finder Info window on the startup volume ("Macintosh HD," unless you gave it a different name.) Check that you have at least 9 GB of available space, as shown in the window. If you don't, copy as many files as necessary to another volume (not another folder on the same volume) and delete the originals. Deletion isn't complete until you empty the Trash again. Do this until the available space is more than 9 GB. Then restart as usual (i.e., not in safe mode.)

If the startup process hangs again, the problem is likely caused by a third-party system modification that you installed. Post for further instructions.

Step 9

Launch Disk Utility in Recovery mode (see Step 1.) Select the startup volume, then run Repair Disk. If any problems are found, repeat until clear. If Disk Utility reports that the volume can't be repaired, the drive has malfunctioned and should be replaced. You might choose to tolerate one such malfunction in the life of the drive. In that case, erase the volume and restore from a backup. If the same thing ever happens again, replace the drive immediately.

This is one of the rare situations in which you should also run Repair Permissions, ignoring the false warnings it may produce. Look for the line "Permissions repair complete" at the end of the output. Then restart as usual.

Step 10

If the startup device is an aftermarket SSD, it may need a firmware update and/or a forced "garbage collection." Instructions for doing this with a Crucial-branded SSD were posted here. Some of those instructions may apply to other brands of SSD, but you should check with the vendor's tech support.

Step 11

Reinstall the OS. If the Mac was upgraded from an older version of OS X, you’ll need the Apple ID and password you used to upgrade.

Step 12

Do as in Step 11, but this time erase the startup volume in Disk Utility before installing. The system should automatically restart into the Setup Assistant. Follow the prompts to transfer the data from a Time Machine or other backup.

Step 13

This step applies only to models that have a logic-board ("PRAM") battery: all Mac Pro's and some others (not current models.) Both desktop and portable Macs used to have such a battery. The logic-board battery, if there is one, is separate from the main battery of a portable. A dead logic-board battery can cause a startup failure. Typically the failure will be preceded by loss of the settings for the startup disk and system clock. See the user manual for replacement instructions. You may have to take the machine to a service provider to have the battery replaced.

Step 14

If you get this far, you're probably dealing with a hardware fault. Make a "Genius" appointment at an Apple Store, or go to another authorized service provider.

Hello,

i have MacBookPro 15'' Mid 2011, after updating to 10.10.4 system does not boot successfully,

I'm unable to boot into safe mode as FileVault is enabled.

followed the steps you lited w/o luck

Did you solve your problem. Do not tell me you have to recover from Timemachine.

I also have this problem from yesterday. Stupid App store download and install the update, but the process bar goes 30% and shut down repeatedly.

What a stupid decision to update. I lost a lot of data which were prepared in the passed three days.

Hey,

Like you said, had to recover from timemachine.

but I did manage to recover my data over the past few days.

installed Yosemite on a removable drive, booted from it then recovered my data from the HDD after I typed the password so the drive would mount.

(HDD is encrypted with FileVault 2)

Several hours to extract the data, now installing a fresh copy of Yosemite and will install the 10.10.4 update from a combo file.

oh wait, looks like apple did pull out that file!

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!

I was trying to do many ways and almost gave up and fornatted my drive. However, I am glad that I didn't do that. By following the above procedures, all of my data and settings were being corrected AFTER the above steps. I was able to boot and no problem at all. No more stop/prohibit sign!!!

Ive been having the same problem with my Mac Pro (2008, 20gb RAM, 256mb + 2gb graphics cards)

10.10.3 worked absolutely fine. 10.10.4 does not boot at all. Bar freezes at 50%, crashes repeatedly.

Apple should really test these updates before they release them, as this is really irritating when you rely on one of these machines to do your job.

SO has anyone found a work-around besides booting from a partition or re-installing Yosemite? Does that mean we just keep it on 10.10.2 or whatever the last boot was and NEVER update to 10.10.4? I guess that means I'm not planning on updating to El Capitan...

Apple is really starting to screw over Designers with these updates. We've relied heavily on their technology for years to do our jobs, and now they're kind of ignoring us for the mega-consumer market, and it's just getting really irritating. Get it together, Apple.

Thank you guys for suggesting the booting from partitions! I'll have to try that tomorrow.

After trying to update to 10.10.4 I got the same result - failure to boot (system shuts down after ~40% of the boot progress bar).

A few recovery notes and observations:

• In order to start internet recovery on Mac Mini - hold option+command+R when turning power on
• Once in recovery mode, I opened disk utility and found that the "Macintosh HD" partition was 100% full and that must be caused by the failing update, because it was fine before the update, I had only XCode and one project installed on 1TB hard drive.
• All tools in disk utility failed, including verification, repair and erasing of the partition, it said that the partition must be reformatted
• There is no reformat button in disk utility, so it has to be done from command line - open terminal from recovery mode menu.
• The right way to do it from command line (as I understood later) is probably using diskutil reformat, however I got lost in command line tools and actually re-created the partition using gpt and newfs_hfs command line tools
• After the partition was re-created I got back to graphical Disk Utility and it was happy
• However, the option of reinstalling Yosemite from interned did not work saying that it can not write information to disk
• After another restart and booting into internet recovery mode, the "reinstall Yosemite" option worked and now I have a working machine.

Hope this helps.

Any other helpful hints? I have a 27" with the Samsung SSD and right after the update, I get the status bar to about 40% and then the circle with the line with a gray screen.

Igor thanks for your suggestion. I will have to try that. Did that reformat your disk doing it that way? If so, were you able to backup your hard drives before? I'm trying to figure out if there's a way I can even back up the hard drive without it powering on completely.

@Nynd good luck getting a samsung SSD to work.. Mine wouldn't run on Yosemite at all. I wound up returning it to Amazon for a refund.

Yes, I had to completely reformat the partition, loosing all the data.

The good news is that you can still make kind of backup before doing that

• In the main screen of the recovery there is a main menu in the top part of the screen
• From that menu you can open a terminal window
• You can than use command line to copy your data folders to other disk (or usb flash memory)
• You can see both your hard drive and the external disk mounted under /Volumes
• Then you get to /Volumes/YourHardDiskName/Users/YourUserName/Documents
• cp -r YourImportantFolder /Volumes/YourUSBDriveName

This worked for me - all my folders files were there so they could be copied.

So if its the Samsung SSD, what other brand can I use that would avoid this circle with slash and allow me to load normally? Can anyone explain what is happening as its trying to start from the SSD? Why does it barf 40% of the status bar and then show that probationary sign?

Startup - prohibitory sign at OS X bootup

Startup Issues - Resolve

Startup Issues - Resolve (2)

Startup Issues - Resolve (3)

Thank you. I had the same problem that others in this thread are reporting—progress bar freezes at about 40% after 10.10.4 upgrade. Step 4 in your sequence (resetting the NVRAM) took my system to the point where I could restore from a recent Time Machine backup.

Hi,

I have the same issue after OS X 10.10.4 update. I could not boot up in safe mode and the Mac still cannot boot after I reintsall Yosmite, reset SMC, reset NVRAM, fsck -fy thing. I read http://www.macworld.co.uk/news/mac/steps-take-when-your-mac-wont-start-3423817/

All failed. I believed I made the mistake of jumping to reinstalling OS X too fast. I decided to repeat the whole thing again and follow the steps sequentially, all still failed until I reached the final step of installing OS X. I got it back.

I did not dare to try the 10.10.4 update again. It is still there in the App store