El Capitan won't Boot after update

Starting up in safe mode worked for my situation.

As the computer started up in safe mode, El Capitan finished installation with no problems after restart.

macbook air 2011, stuck at boot screen after osx update...

This helped

https://www.justinsilver.com/technology/os-x-el-capitan-10-11-1-hanging-on-boot- fixed

1) boot to recovery mode (hold cmd-R at boot)

2) in terminal compare kexts in "/Library/Extensions/" and "/Volumes/Macintosh HD/Library/Extensions/"

and remove some kexts from "/Volumes/Macintosh HD/Library/Extensions/"

in my case HP and Canon printers

3) reboot and everything works again

I had the same issue trying to install the upgrade to el capitan. I have a 2015 iMac. I realized that I had my external hard drive connected, and a memory card inserted as well.

As soon as I removed them, the install resumed and the apple logo with status bar appeared. (Wish I would have thought of this three hours ago.)

I know this is a shot in the dark, most people aren't quite as dopey as I, but I figured it was info worth sharing.

Cheers.

After upgrading to El Cap [late 2011 MacBP] I had all these issues as well; stalled on boot up after apple logo, wouldn't go into Safe Mode then finally did, then crashed out of Safe Mode when browsing - then with restart fell into a boot looping scenario. I had already taken it to the Mac shop for checkup so knew that the HD was okay. I called Apple support and did all the rudimentary checks with them [unplug externals et al] but it wasn't until I read about kext files here that I started understanding this was tripping up the boot process - so thanks guys and gals.

Turned off all printers in Sys Prefs

Turned off Time Machine

And for fun I deleted Chrome b/c I kind of hated it from the beginning. Probably the best advice I got from Apple support was to not use Chrome.

Restarted on a dime.

This has also rid me of fan issues which have plagued me and my misadventures with Chrome.

Best

Spoke too soon. Repeatedly crashes in Safari 9.1 using Google Maps and some websites - using Flash I believe - screen goes black, then back to reboot loop. Did and Internet Recovery for kicks and seems ok but this is getting old, fast. Meh. Advice on reverse engineer back to Yosemite ?

Thank you so much doranchak. This fix just saved my bacon. This exact scenario happened to me just now after applying software updates that brought me from 10.11.4 to 10.11.6. Machine booted, but could not log into my account - spinny wheel just like you reported.

I did one thing slightly differently: instead of getting into the machine remotely, I started in single user mode and enabled the root user. I had done that long before I found your suggestion -so I was then able to log in as root and move the files around as you suggested. Of course, other might also just start in SU and run rm to remove the files that way, too.

Good stuff. Thanks again.

Paul

yes it froze during the update after an hour I switched it off. Now on power up on a grey screen the password request appears I enter the password lines appear in the top left hand corner. The screen goes blank and loops back to the password screen.