Yosemite: boot hangs at 50% percent

UPDATE

It seems that repairing disk permisions and repairing disk, worked.

Right now I am running Yosemite 10.10.1 but it is extremely slow. I can perform one action per minute or more. I couldn't check if FileVault is turned on, or what is the status of it, if is already encrypting or if it is done.

If it is done, I guess I will turn off encryption from Disk Utility.

I have been having this problem (boot hanging at 50%) with my MacBook Pro, but the same thing has been occurring sporadically with Mac computers at work. So far, resetting PRAM and SMC haven't changed anything, nor have repairing permissions or repairing disk from recovery mode, but booting into single user mode and then typing "fsck -fy" and then "exit" allows the machine (usually) to boot normally into Yosemite. The "fsck" may be unnecessary, but I have been doing that because I don't want to use up time figuring out whether it's necessary or not. On my MBP, this has worked pretty consistently. It takes longer and is a bit of a pain in the dupa, but I am hopeful that some future OS update will fix the problem.

According to this thread the problem appears to be related to Yosemite and Active Directory, specifically the OS trying and failing to re-create a user profile after a hard restart. My wife is currently experiencing this problem but is on an international trip and is not comfortable troubleshooting in the ways a suggested fix demand. I had mentioned in a reply on the other thread that our university's preferred solution is to re-image the affected machines back to Mavericks.

I had this problem, too, this morning. MacBook Air was upgraded to Yosemite, and this morning it got stuck at 50% of the boot sequence. I tried booting into Recovery mode, repaired disk and permissions (all ok), tried safe mode, and single user mode, and resetting PRAM (to no avail), and the Hardware Test (all ok). Eventually, I booted using Verbose mode (Command-V at startup) and found that it got stuck at the line:

kauth external resolver timed out (1 timeout(s) of 60 seconds)

I use this MBA as part of an Active Directory, mobile user MOE configuration at our university. When I arrived at work, I wanted to reinstall Yosemite, but noticed that it wouldn't connect to our wifi network during Recovery mode (WPA2 Enterprise failed to connect), so I borrowed an Ethernet to Thunderbolt adapter and connected via Ethernet. Eventually, it rebooted as normal. I have since removed the Ethernet to Thunderbolt adapter and switched back to wifi, and it still reboots ok. Fingers crossed.

Still no sign of a fix for this? Very, very frustrating.

I work in a computer lab and it's happening consistently on one of our iMacs. Not happening at all on any of the new Mac Pros. Has happened a few times on the old Mac Pros we have.

OKAY, COME ON APPLE,

I've been resetting my SMC at least once a week. It works, for a while then, after a few days the spinning wheel comes up for a minute then things run slow, yet they still run, then another minute later we get a spinning wheel where nothing will open, things are mostly frozen, then things unfreeze. After another SMC reset and PRAM reset things work normally again for a few days.

This is all a second issue I'm having with Yosemite that I was never experiencing with Mavericks. The first as I posted earlier was with the boot hanging at 50. That no longer happens after resetting the SMC 5 times.

In some other reading the subject of older mac hard drives came up however I'm really not sure what that's about. I know my mac is older and I'm looking to upgrade within the next year however for now I need to fix this issue. My 2009 isn't THAT old that it shouldn't work with the most recent OS. I'll reserve my frustrations for more healthier outlets however thought I should at least update this community by letting you all know that I'm STILL EXPERIENCING PROBLEMS WITH YOSEMITE!

Thanks.

This issue has happened to me as well and I just managed to fix. None of the previous solutions worked, so I finally resulted to going into single user mode (cmd + s) and checking the log file (tail -n 100 /var/log/system.log) and there I found the error. Before I explain what was my error and how I fixed it, I urge everybody to read the log before jumping to reinstalls, zapping PRAMS etc. Sometimes the error might be quite straight forward and individual, even though the symptom is shared with other users.

== This is just for info, read above to see how to approach your case ==

My concrete situation is that while cleaning some disk space I have removed everything from the /var/folders/ which got quite crowded. Now there is debate online whether you are allowed to delete the contents of that folder or not, but I leaned towards the arguments for doing that. The system started behaving strangely (seeing errors never seen before) and I finally decided to restart which got me to 50% boot hanging. And then I followed various only instructions to attempt the fix. Nothing worked.

Finally, before taking in the laptop to my universities service center (and probably not getting it back until after holidays) I said let's try to figure out what exactly is happening. So I started digging into the logs and there, right away, on the first try, I identified that the system was hanging with this line: libcoreservices: _dirhelper_userdir: 316: stat: /var/folders/zz/zyxvpxvq6csfxvn_n00000sm00006d/: Permission denied

I mounted the disk (mount -uw /) and fixed the permissions (chmod 755 /var/folders/zz) and tada, I'm back to on my mac.

Now your error might be quite different, but you can start the process of identifying it by checking the logs. Then you might find the more permanent solution.

====

Have a nice week

SO, I have read this thread, and I have tried all of the solutions suggested, some times they work, but most times I have the same hanging upon boot issue. Sometimes resetting PROM and NVRAM works, sometimes it doesn't. SOmetime a simple fil system repair works, some times it doesn't.

I currently have 12 of 109 Macs unusable where I work. Some of them are laptops, some are iMacs, some are old, some are new. All are running 10.10.

Hello!

Just remember that when you reset the SMC you have to disconnect all peripherals from the Mac. Think external HDD's, SD Cards, Displays, etc, etc.

Additionally,

I’ve offered the steps below to similar issues in the past and they helped out getting to the solution (or at least find the cause). I suggest them to you too in this case. It will take you about 45 minutes or less to do these, depending on how bad the problem on your Mac is as well as your internet-connection speed.

The goal here is to boot your Mac to the so-called Internet Recovery partition where you’ll have a chance to repair the disk and the disk permissions using the Disk Utility and Password Utility. This might solve your issue and even if it doesn’t- it’s still a decent maintenance step to perform. These steps won’t erase your data or reinstall your Mac in any way if you follow instructions carefully.

Here’s how:

1/ Make sure your computer is completely shut down.

2/ You’ll have to be quick next: Press the Mac’s power button. As soon as you either hear the loud chime, or see the display light up - usually after a second or 2 - on your keyboard press [alt]+[cmd] + [r] Keep these keys on your keyboard pressed until you either see a spinning globe with the text “starting Internet Recovery” You might have to connect to your Wi-Fi network before you can continue here.

After a few minutes, you’ll be presented with a Utilities screen. This is the Internet Recovery partition. If this step is already giving you problems, try using a USB-keyboard. It doesn’t have to be an Apple-keyboard. If you have a Windows-tailored keyboard laying around, use the “Windows-flag” key in stead of the [cmd]-key and it should also work.

3/ Choose Disk Utility and click [continue]

Disk Utility will display your computer’s harddrive in the left column. The default name for it is “Macintosh HD” and is usually the second one from the top. Click on it and click on the [verify disk] button. This will check your “Macintosh HD” harddrive partition for errors. If found, click [repair disk] unless you have a Fusion drive in your Mac and it says [fix] instead of [repair disk] please tell us before you continue! For a screenshot of what I mean, check this article from Apple: http://support.apple.com/en-us/HT202574

4/ Once done with the verifying or repairing of your “Macintosh HD” click [repair disk permissions]

This will check your partition for permissions errors. A common myth about this feature is that it will fix all permissions issues on your Mac, which is not true, but it will fix most systemwide issues. Also, here is a list of error messages that you can safely ignore if they pop up:

http://support.apple.com/en-us/HT203172

We’re ready to reboot your Mac now. Click on the Apple Menu and choose “startup disk” Choose to boot from “Macintosh HD” Please let us know if this solved your issue, or if the steps above did not work, or could not be performed for some reason.

What does your log say?

Hi again,

Thank you everyone for the help however I still have no clear fix for this issue in sight. Recently my late 2008 machine has been acting up again. Becoming unresponsive for a few minutes at a time then returning to normal. this unresponsiveness is NOT program specific. After repairing permissions and zapping PRAM and SMC on more occasions than id like my machine is still on the fritz sincr this update to Yosemite. right at this moment I'm restoring from a time maschine back Up to the most recent settings for Yosemite that worked but have already done this once before and eventually (now) am experiencinh the same problems.

ALso after doing the last restore from from backup I didn't experience the boot hanging at 50% for quite a while but did start having these moments of unresponsibeness. Then yesterday after a few weeks of the boot not hanging at 50% it was stuck there for 2+hours before I did a hard reset and am now restoring. Really annoying and a BIG problem for my satisfaction with apple right now as Mavericks was running flawlessly.

i believe you were asking me for a log however I'm not sure how to get one to show acurately what the issue is as when it freezes up or hangs at 50% it doesn't "crash" so there's no error report. If there is another way to get some kind of log would someone care to tell me how.

AGain I really do appreciate the help on this.

thanks

Hi, I do understand your frustration.

Even if there is no crash, there is a chance that something is recorded in the log that might indicate exactly where is the problem. My suggestion is that you remember the exact time of when the computer freezes (if that happens in the running mode) or when you last booted it up. Then restart and enter the single user mode (Cmd + S). Once there you should be able to explore the log (tail -n 100 /var/log/system.log). If you don't find your time in the log, play with the number 100 (and other parameters in tail command) to get more information. When you find the messages that appear around the time your computer freezes (or time you estimate it reached the 50% and started hanging) copy those lines and post them here to see if more information can be identified.

Thanks a lot for the direction! 🙂

I've got a company laptop and it uses active directory. And domain user has been setup on the machine. I use VPN to get on the network.

What I did to resolve the issue is that ran OS X Recovery by pressing command + r at startup.

Then disabled the wifi from top right corner and restarted the mac.

And I could login without any delay.

I have the same issue, but after resetting the NVRAM i couldn't even boot into Safe Mode. Instead it just become the dreaded ? Startup Folder icon.

I'm bringing this to the Genius Bar tomorrow. I really hope they know about this issue...

whizzo's referenced link is the only solution that worked for me after trying all other suggestions in this thread.

Here is the details from that link that worked for me (Note you will have to rebind the machine to the domain) -

Steve MaserDec 2, 2014 7:16 AM Re: iMac not booting after upgrade to Yosemite
Re: iMac not booting after upgrade to Yosemitein response to Steve Maser

So, this is not necessarily a "fix" -- but a potential way to get back up and running.

Boot into Single-User mode

and mount the drive with:

/sbin/mount -uw /

Then delete this directory:

rm -rf /Library/Preferences/OpenDirectory

then "reboot".

This, of course, unbinds the computer from Active Directory. So it's not going to work for everybody.

It works for us as our managed machines will rebind a machine to AD automatically if it becomes unbound for some reason (when an hourly script is run on the managed machines.)

Out of everything I've tested (PRAM zap, safe boot, etc.) -- since the problem seems to be specific to machines bound to AD -- removing the AD configuration in single user mode may be the only "sure-fire" way around this issue (until Apple fixes it.). We've tested machines where the PRAM zap/Safe Boot has to be run multiple times to make it work and no amount of multiple-just plain-reboots (which seems like it can work eventually on most computers) was working

YMMV, of course... If you don't have a way to automatically rebind machines to AD, you'd then have to manually rebind them. (And, obviously, this solution a serious pain for a managed lab, of course where you can't single-user boot remotely...)