Q: Yosemite Upgrade - iMac mid-2011 - Stuck on white progress bar screen at about 50%

Did you press and hold command+R before the Apple logo?  CMD+R is recovery mode.  That should be working, but possibly the upgrade did not complete upgrading the recovery partition. 

I'd press and hold SHIFT instead, and see if you can get into safe mode.

Yes I pushed Command R right after I heard the chimes, and I cannot figure out safe mode either. I push and hold shift when I hear the chime and then release when the apple logo appears but then it just proceeds to the boot screen and being stuck at 50% again. I must be doing something wrong but I can't figure it out.

hi... i did this. how long does it take when you reboot after you turn offthe WiFi? should it zoom by like in 5mins? or will it take 30 to an hour?

I'll have to think on that one.  I would try using the command key on the other side of the keyboard, just to rule out a sticky key.  Also, you might try keeping the command key held just maybe 5 seconds longer.  Any chance you have a spare USB keyboard lying around?

I must done something wrong. I tried to follow the instructions above but I have now lost everything. It asked me to restore from Time Machine and wiped out my computer. Now it says it will take nearly 7hours to restore. The time keeps going up though

I'm having this problem too, but in my case the upgrade itself appeared to go fine, and I only got into problems having tried (and failed) to do various application updates and got to the point where I had to hard kill the machine to shut it down.

On subsequent boot attempts, left to its own devices twice now it has got to 50% (eventually!) and no further.

With a Cmd-R reboot I was able to get into recovery mode and do a disk check etc.

I've left it in the office stuck at 50%, so in the morning I'll try the "disable Wi-Fi" trick.  I had noticed that in recovery mode the Wi-Fi adapter claimed to be connected, but had no IP address.  ISTR that the WPA password on that particular SSID has been changed recently, so it does seem likely that the boot hang is related to it trying and failing to connect to a particular Wi-Fi network.

For everyone having issues installing Yosemite because of the progress bar stuck for hours and hours with no luck and if you have any anti virus installed ( Norton, AVG, McAfee, Avira, etc ), follow this:

- Boot up in Safe Mode

- Finder > Applications > Uninstall Anti Virus

- Finder > Go > Library (press the Alt key for the Library to appear)

- Remove all content from following folders (not the folders themselves!) :

~/caches

~/launchAgents

~/saved application state

- Finder > Go > Computer > MACINTOSH HD

- Remove all content from following folders (not the folders themselves!) :

~/caches

~/launchagents

~/launchdaemons

~/StartupItems

~/preferences/system configuration > Remove only the following files:

- com.apple.Boot.plist;

- com.apple.PowerManagement.plist

- Empty Trash

- Restart

That should work like it has worked for other people

Hope it will be helpful...

I have a Mid 2011 iMAC and encountered the grey screen of death and the disappearing progress bar from **** when installing Yosemite.  Majority of the problem stems from Yosemite installation not being completed and lagging in the background upon reboot. Here are some easy fixes:

1. Restart your computer by holding the power button for 10 secs. Upon reboot and chime hold down the SHIFT key. Be patient, for it can take some time for the Safe Mode screen appear.
2. Once in Safe Mode you should see a Yosemite completing installation pop-up box appear. Let the Yosemite run its final installation piece and restart normally by selecting the option form menu bar. Do not use the power button to restart your computer once in Safe Mode.
3. Once you restart, there should be no more grey screen or progress bar issues. Login as normal to your user profile

If you have tried this to no avail, then you can reboot and run Disk Repair utility or try a fresh reinstall of Yosemite by holding down the OPTION key upon reboot and chime. You may also try resetting the NVRAM an PRAM by retarting and holding down SHIFT + OPTION + P + R upon reboot and chime.

Good Luck

I have a Mid 2011 iMAC and encountered the grey screen of death and the disappearing progress bar from **** when installing Yosemite.  Majority of the problem stems from Yosemite installation not being completed and lagging in the background upon reboot. Here are some easy fixes:

1. Restart your computer by holding the power button for 10 secs. Upon reboot and chime hold down the SHIFT key. Be patient, for it can take some time for the Safe Mode screen appear.
2. Once in Safe Mode you should see a Yosemite completing installation pop-up box appear. Let the Yosemite run its final installation piece and restart normally by selecting the option form menu bar. Do not use the power button to restart your computer once in Safe Mode.
3. Once you restart, there should be no more grey screen or progress bar issues. Login as normal to your user profile

If you have tried this to no avail, then you can reboot and run Disk Repair utility or try a fresh reinstall of Yosemite by holding down the OPTION key upon reboot and chime. You may also try resetting the NVRAM an PRAM by retarting and holding down SHIFT + OPTION + P + R upon reboot and chime.

Good Luck

The Command R method by SATopWater did not work for my 2009 MacBook Pro. However, the SHIFT method by Sparkleberry did work and now my laptop is upgraded and works normally.

Thanks u all guys.

After waiting for around 12 hours I tried this and it seems to have worked. Apple if you are reading this you should give this person a job.

anyone else still having problems?? i've waited a complete 48hrs and there was no progress. I tried the Command R and the SHIFT procedure and it doesnt work, still goes to the start-up screen (grey apple with black bar / sometimes white apple with white bar). i have also tried the doing a Recovery HD but still stuck on the start-up screen. HELP!! please and thank you

Thank you for your clear, step by step solution to this problem. This worked for me. Most of what I read in these forums is incomprehensible and rather intimidating. So thanks again. At least I get my life back now. A pity Apple has apparently not yet seen the need to provide support for those struggling to get their product to work properly. Not their problem?!

Thanks to SATopWater, this worked for me too.

Mac pro mid 2010 (5,1). I had also to clear the nvram before (Cmd + Option + P + R), because after the startup, no sound (chime) was hearing and Cmd+R or shift doesn't working.

After reboot, I got to recovery mode, I turned off WiFi, and after the reboot, the installation was fineshed! So, thanks again.

WinnieTabz, check my case, 2 posts below yours. Try to clear your nvram, and you' ll be able to go to recovery mode after that.