Yosemite: boot hangs at 50% percent

And now, does your imac still show a progress bar during boottime?

A progress bar during boot is the New Normal in Yosemite. It does not mean you are booting in safe mode. Although, when you boot in safe mode in Yosemite, you still get a progress bar also.

Are we aware of any progress on this from Apple or permanent fix? Apple appear to actually deny this is an issue at all, let alone a major problem, which it is.

As head of Infrastructure at a large E-commerce company, this is NOT a small problem & personally I find it a disgrace that Apple's only solution is to format the hard drive & reload the OS. Especially when you consider that these glorified PC's cost us nearly £1800 and over half of the 100 we own, have had this problem in 1 month since upgrading, with a quarter requiring a complete OS reload.

I've written already several times that to be able to help you, we need to see the logs.

Apple is not going to address this issue because this is not AN ISSUE. This is a symptom of MANY POSSIBLE ISSUES. There are a lot of things that can go wrong at the last stage of the booting (the last 50%) and if something happens that is critical the boot it self will freeze. The only thing Apple could do here is maybe throw you some kind of "error" message (like blue screen of death from Windows) but I believe this is agains their usability policy. Although, seeing how many of you complain without even investigating what is actually wrong, maybe that would indeed be something that is needed.

I've been suffering from this problem since I first installed Yosemite. The first time it happened was upon initial installation. There I found out there was a drive corruption which was fixed by Disk Utility and all was okay. Then, a few days ago, I decided to do a shut down and restart (I had done one the day before without a problem.) The machine hung. Repeat, hung. Repeat, hung. Zapped PRAM and went into safe mode then restarted and all was okay.

Restarts, for me, are now not a problem. I am terrified of doing a shut down, and won't risk it. I simply don't have four hours to waste on this. Since I am using a mid-2009 MacBook Pro I just put the machine to sleep, wake it the next day, go on my way, and once a week do a restart and all seems okay. This machine uses lots of add ons so I'm wondering if one or several of them are causing the problem. I say that because I have an iMac of similar vintage which essentially acts as a dummy terminal for calendar and internet, and I hard restart that machine every day without a problem.

I also find the machine now takes forever to do things the first time around. The hard drive seems to be constantly working when I go from battery to AC, or after restart. It almost seems like it's reindexing the entire drive. And I don't know about anybody else, but booting into safe mode takes FOREVER, and uses an incredible amount of processor resources, so much so that I have to turn on an external fan to prevent the machine from overheating. This is why I will not shut the machine down.

I've been using Mac since System 7.5. In all honesty I find Yosemite to be *the* worst release Apple has done in all these years. Ever since Snow Leopard, the quality has gone further and further downhill. This is very sad.

Wow. This is a headache for my school lab. I agree with all the findings that implicate macs that are connected via Active Directory and that this happens after an abrupt power off situation (normal shutdowns dont seem to bring up this issue).

Booting into safe boot mode works, but its hit and miss... many times safe boot just doesnt come up and I have to restart over and over and over and over (you can sense the kind of morning Ive had).

I tried something different and this seems to work better-- shutdown the computer when it's hanging (force shutdown by pressing the power button), start it up and press command-r to start up in recovery mode. I made sure to get online somehow (as to "activate" the internet connection)-- what I did was click on the "Visit Apple Support online" option and clicked around a bit. I then restarted the computer and it booted up fine. This is quicker than fiddling around with safe boot mode for me.

Just thought Id share in case this solution would work for you.

Further to my response above, the issue has happened again twice. This time I was able to get my MacBook Air to start up by rebooting into single user mode (command-S), and then follow the on screen instructions to check and mount the disk, and then to "exit" to continue the normal boot up process, which now in fact finished ok.

I don't think this is an Apple issue. It's Active Directory, a directory service that Microsoft developed for Windows domain networks. Unfortunately, our university uses this to control all Macs together with Casper. Easy fix: Remove them:

System Preferences > Users & Groups (log in as admin) > Login Options > Network Account Server > Unbind

If you are also burdened by Casper, open Terminal and enter:

sudo /usr/sbin/jamf removeFramework

YMMV.

On my 2011 iMac I just tried an SMC Refresh, and PRAM, Permissions & Disk Repairs etc all to no avail. The hang time at 50% was really frustrating.

Decided to do a re-install of OS from Safe Mode, and that seems to have done the trick.

Our school also uses Active Directory and here's what we have confirmed:

1. The hang occurs only after the power is cut (either by pulling the plug or holding the power button) AND an Active Directory user has logged in since the last boot.

2. Booting to Single User mode (cmd-S), typing exit, powering off and back allows the machine to boot again.

3. The log files don't seem to show much since the machine is hanging during boot and therefore not showing what it's hanging on.

It's not just an Active Directory problem. I don't have Active Director on my machine. I am not connected to any system looking at Users and Groups. And I've had this problem several times. I think smwang99 has something going because I think it has to do with whether you are changing the power source between shut down and power up. On my PowerBook, if I shut down using battery power, then re-start up using AC, that's when I hang. I can't say the reverse is true. I've also noted that if I wake from sleep on battery power and everything seems okay, the minute I attach the AC adapter, the hard drive starts whizzing and whizzing like it's either indexing or doing some maintenance routines, and does so for quite some time.

DrSFG wrote:

I think smwang99 has something going because I think it has to do with whether you are changing the power source between shut down and power up.

In the single instance I had to deal with this it was an iMac 27", as such no power source changes, but a forced shutdown was made. Perhaps there are multiple causes or these are somehow related.

Maybe, because now the system didn't know status when you restarted. I have a iMac 15"(??) and I turn it on and off every day and have never had a problem with Yosemite. But my MacBook! oy vey!

About 150 Macs here. Thankfully most are locked down but a few people have updated themselves to Yosemite.

We have the same problem on a mixture of machine setups - some are AD, some not.

Varying success with PRAM / SMC resets.

All very, very annoying and consuming much needed resources to unpick this mess.

Hello,

Even though I have a very similar problem (stuck at about 50% on startup) neither of these solutions work for me because no matter which key combinations I press on startup (and I do have a working keyboard) I get the same loading bar. An exception is the Verbose command: Cmd+V. This tells me my system got stuck at the lines:

3.600987: ATH tunables:

3.602180: pullmode[1] txringsize[ 256] txsendqsize[1024] reapmin[ 32] reapcount[ 128]

Edit: After a long wait it adds the line:

disk0s2: I/O error.

It might be a malfunctioning HDD.

I'd love to get into a disk repair mode or would be able to boot with the "c" command into an OS X boot USB stick or see a log file, but I'm not even able to get there because of the stuck loading bar. For the record: Of course I tried reseting PRAM and SMC. Makes no difference. I begin thinking this might be a hardware or firmware issue.

OS: 10.10.1

iMac 27" Late 2009

Please help!

I had a very similar symptoms recently, and I think we have tracked down the problem. It is not network related. I described it on MacInTouch.com:

A client brought me an iMac that would not boot. He had recently upgraded to Yosemite and had been using it for some weeks, but this symptom popped up unexpectedly. The new Yosemite boot screen with its progress bar would make it about one quarter of the way and then the screen would just go white and nothing else would happen (I do hear some disk activity for a short time after this happens; can't see anything helpful in the logs).

The first thing I tried to do, of course, was boot it in Safe Mode, which worked fine. (Incidentally, every computer running Yosemite in Safe Mode has weird venetian-blind graphic effects, which I guess is normal.)

The first assumption is that some startup item is interfering. This client runs a unusually clean system; the only third-party program is QuickBooks. There were no startup items anywhere, aside from iTunes Helper.

Ran DiskWarrior, permissions repair, zapped PRAM, checked SMART, etc.; things were working fine, so I returned the computer. Back in its old digs, it promptly refused to boot again.

I spent about a day finding all kinds of people with similar problems online, most of which turned out to be network-related, not applicable in this case. I reinstalled Yosemite and did some other things. It would be fixed and then misbehave again after being unplugged for a while.

At this point I connected my diagnostic disk which has partitions from Leopard up through Mountain Lion. Surprise surprise, this iMac will not boot any of those systems unless it's in Safe mode.

I wonder if there is an intermittent hardware problem with the graphics card or logic board. Has anyone ever seen anything like this before?

At the moment, it has decided to behave again, but I'm sure it will act up again after I return it. At that point I will try booting to an external clone, but based on the fact that the same thing happened with all my own diagnostic drive partitions, I don't have high hopes. I guess at that point it will go into the shop for hardware testing which I am unable to do.

While I searched for solutions, the client has been working in Safe Mode.

Many people online with the same problem found it was related to Active Directory or some other networking issue and Yosemite.

Jaap Vander Veen, however, reported a different experience:

Recently I had the same issue with a 2008 iMac.
After quite a bit of troubleshooting, I concluded the cause of the trouble was probably a faulty graphics card.
In this case, I moved all kext files with ATI in the filename to the desktop (while booted in safe mode).
That did the trick. Without these kext files, the iMac booted as 'usual' - that is, without graphics acceleration.
My conclusion is that the part of the graphics card that takes care of graphics acceleration (which is disabled in safe mode) is defective.

Well, the client called me back because the computer was acting up again, and I removed four ATI kext files from the System folder. Now the computer is booting fine again, and rather than having to work in Safe Mode as he had been, he now has sound and printing again. He does have to live with the venetian blind effect, and he understands that his computer probably has an intermittent hardware problem that will most likely get worse as time goes by.

Thank you Jaap and the MacInTouch community.

Hard shut down and boot via safe mode (shift key at chime). It takes a looooooonnngggg time to boot via safe mode. Then use Disk Utility to repair permissions and check the drive. Repair the drive if necessary. Then restart the machine. That worked for me. The problem seems to be with hard restart after shutting the machine down as opposed to a simple restart from the desktop.