Yosemite: boot hangs at 50% percent

Hi,

we have a lot of iMacs hanging at boot since the update from Mavericks to Yosemite.

They are stuck at 50% on the progress bar.

All discussions we have found about it say that this is caused by TRIM on SSD devices, and that we must disable TRIM.

But all our iMacs are HDD, so this solution doesn't apply.

This seems to workaround the problem for us:

Reset NVRAM with CMD+ALT+P+R

Then boot in safe mode, http://support.apple.com/kb/ph14204

Then reboot normally.

I hope this helps people who get the same problem.

iMac, OS X Mavericks (10.9)

Posted on Oct 18, 2014 10:46 AM

141 replies

e_daniel

Level 1

4 points

Sep 23, 2015 3:58 AM in response to e_daniel

Not a hardware problem, so the solution was to wipe and reinstall the OS.

Nov 3, 2015 10:16 AM in response to DlacVal

Thank you very much. It worked for me.

Nov 22, 2015 9:40 PM in response to IUnderwood

OMg you're my life saver! i tried this in Safe mode then rebooted! It worked perfectly! 🙂 big thumbs up for you mate!

Jan 27, 2016 8:12 AM in response to DlacVal

This is happening to my machine more regularly now, occurring after a re-start following a software update - too easy to link to the update since its the most obvious time for a re-start, rarely perform a restart otherwise.

I usually leave for a good couple of minutes when it may continue (the progress bar), otherwise power off then switch it back on, inevitably there's a pause/hiccup at the same point - 50% of progress, then it continues OK. Dreading the day it doesn't - looking for a maintenance/utility lead to follow.

It did start doing this in late 2015 after an Apple software update.

Apple not exactly helpful in describing/detailing their updates role and purpose.

iMac, OS X Yosemite 10.10.5

Nov 14, 2016 11:20 AM in response to DlacVal

After nearly a week of troubleshooting, starting and restarting, this proved to be my solution. Very grateful.

Nov 28, 2016 12:53 AM in response to DlacVal

This worked perfectly for me, thank you. I didn't bother with the safe mode boot either but all appears to be functioning as it should currently. Saved a minor meltdown on a Friday afternoon.

This thread has been closed by the system or the community team. You may vote for any posts you find helpful, or search the Community for additional answers.

Yosemite: boot hangs at 50% percent