Mac Troubles - 5K iMac not Booting after installing El Capitan

A few weeks ago my 5K iMac seemed to be running slowly while using Photoshop. The usual fix is to simply restart, refresh all systems and get back to the task. Not so this time. I heard the usual Mac chime on restart but that is far as it went. A black screen, a bright Apple logo and a grey progress bar with NO progress. 

This is what I was hoping to see, some progress, but just a grey bar. The boot process seemed to be halted somehow.

This is what I was hoping to see, some progress, but just a grey bar. The boot process seemed to be halted somehow.

Anyway to 'cut a short story long'  (ha) I did all the tricks I have learnt over the years to get other people's Macs back up and running, but to no avail. It simply stalled every time on restart! Bummer!

Now I had installed El Capitan OSX 10.11 a few days previously, so was it something to do with the new operating system?

Call Mac Support by phone. As usual they are very helpful. But the only options they could come up with was to reinstall El Capitan and call back if it did not fix the issue. Fortunately when I did update to El Capitan I also made a bootable USB El Capitan installer thanks to the excellent advice from Dan Frakes at MacWorld. Using the USB drive I could re-install El Capitan in about 20 minutes instead of hours it would take downloading the software from Apple. Unfortunately, even with a new OSX, the iMac still would not boot. After getting back to Apple support, they advised the only option was to erase the hard drive and do a clean install. Of course they double checked with me that I had a full backup. Thanks Time Machine.

After a full erase of the HD and re- install of data,  the iMac still did not boot. Advice was then to take the iMac to the Apple dealer to check the hardware. This took a couple of weeks after dropping it off at Data Parts in Shepparton. After another erase and re-install of El Capitan without my data, the computer booted as normal. Conclusion; the computer was fine but there is a problem with the software. The technician worked on the idea that an installed app was the culprit. He removed a few of the apps that analyse the system such as iStat Menus 5 and CleanMyMac 3. He spent a lot of time working on the issue and finally rang me saying he had solved the issue by removing some apps.

I was very pleased with the news but on returning home and starting up the Mac, it would not boot. Back to square one!
I was charged a reasonably low fee for the work that was done, as it was not covered by AppleCare being a 3rd Party software issue. Seeing I was able to re-install the OSX via USB and get one go at working on the Mac, I decided not to send it back to the Apple dealer but work on it myself. I removed lots of apps only to find the same issue every time I  restarted. A full weekend working on the Mac and getting nowhere. I must have re-installed OSX El Capitan 20 times, removed apps and every time it would not boot. 

In despair on Sunday night I erased the HD, re-installed the OS and did a complete backup from Time Machine, Since this takes a while I checked progress at about 2pm in the morning. I had been Googling the issue for weeks now without any break throughs. Although I had read some references to kernel panics and kernel extension problems. So in the middle of the night I Googled again and by chance came across this post...

It was worth a try even though I don't often solve problems using Terminal. It worked! The iMac booted. The grey progress bar light up with a bright advancing bar. Yeah. It looked much more promising. I was not game to reboot but went to bed feeling much better about the full weekend trying to solve this problem.

Next morning all was well. It was not a dream after all! The iMac booted up as normal and with the Time Machine backup all my files and settings etc were there up and running. So one line of code, removed using Terminal fixed the problem. Wow, if only I knew this a couple of weeks ago. It would have been so simple.

Its interesting to look back. One of the things the technician at the Apple dealer showed me was how to do a Command-V for booting in verbose mode. This prints program code on the screen while booting. I tried this while the Mac was misbehaving and it came up with this code....

Taken with iPhone

Taken with iPhone

You can see near the end: 
Mac OS version:
Not yet set

Indicating the termination of the boot process.

Also note the kernel extension in backtrace is called:
Apparently this is the offending code that was removed.

Now there is software made by Eltima called SyncMate which I had not heard of before and therefore wonder how this kernel extension found itself on my Mac. I am not sure if the problem was related to the recent installation of El Capitan but I doubt it.

All is well now. Its lovely to see the light bar appear when booting up! (Although still viewed with some nervousness).