What was in the September 24, 2020 update that killed my iMac?

Humans make mistakes. Software has bugs. You need to plan for this.

You need to have a backup. I use timemachine and carbon copy cloner. Timemachine for incremental backups and CCC to make a clone of my system. A clone allows me to boot instantly from my backup system. I'm running from my backup system now. Trying to sort out my primary system now because of disappearing data on primary system.

I recommend etrecheck to assist in sorting out performance issues.

I'd run etrecheck. Etrecheck will analyze your machine and software and generate a report. Post results here so others can view.  Experienced users have found the reported information useful when diagnosing problems. The proprietary stuff in the report gets filtered.

Install and run

-- Download etrecheck.  Goto the  EtreCheck  download page.  The download link is at the bottom of the screen

-- Install etrecheck. Goto your download folder. Double click on EtreCheckPro.zip

-- Drag the app to the application folder if you wish.

-- Turn on full disk access for EtreCheck.  This was how macos used to work.  Do it for etrecheck not avast as in the instructions.

Enabling Full Disk Access in macOS Mojave (10.14) and higher | Official Avast Support

-- Double click on etrecheck to run.   The first five runs are free.

An alternative explanation how to install, run and report output for the EtreCheck Application

Using EtreCheck to Troubleshoot Potential… - Apple Community

Explanation of EtreCheck  output by etresoft, the author.

Using EtreCheck - Apple Community

How to report etrecheck data.

1) When the report is done, click on the Export icon.

2) click on "Copy report" to copy to the clipboard

What to do with your report

4) Get back in your web browser and access your discussion. etc.

5) click on Additional text icon

which results in...

6) Paste your report

7) click on "Add Text" button

8) post your post.

Robert
PS. You may find Old Toad's write up helpful.
How to use the Add Text Feature When Post… - Apple Community

sarahara wrote:

I think if we all start a new thread with, say, "Apple Software Update Sept 24 2020 Has Crippled My System", then Apple will maybe respond. So far, discussions are only going under one or two posts. They probably only notice headlines for individual posts, so they probably need to see lots of them.

Flooding these user-to-user help communities will achieve nothing but hinder helping other users. Apple is not here. Apple does not monitor these communities for problems. Use the official feedback or contact channels if you want to notify Apple.

Product Feedback - Apple

Contact - How to Contact Us - Apple

Indeed, all downhill at different speeds since 10.4.11. :(

Safe Boot, (holding Shift key down at startup).

Try the standalone in Safe Mode, but not using Firefox...

https://itunes.apple.com/us/app/macos-mojave/id1398502828?mt=12

I read this reply just now:

VikingOSX

User level:

Level 9

(65,581 points)

macOS

Speciality level out of ten: 1

Sep 29, 2020 1:20 PM in response to Starman35

It knocked the socks off my 2014 MacBook Air that was working perfectly with Mojave 10.14.6 before the 2020-005 update. I booted into Recovery and performed a Disk Utility First Aid, rebooted into Safe Boot mode and emptied the entire ~/Library/Caches folder contents, and then rebooted normally. At that time, I emptied the Trash.

Once the above was done, the Air returned to normal functionality, more or less…

Have you tried booting into safe mode?

Try a safe boot.

    Shutdown your machine.  Hold down the shift

key.  Poweron.  The boot up will take longer than normal

because the filesystem on the startup drive is being checked and

repaired as needed.   All about safe mode including what

features and apps safe boot leaves out. 

Safe boot uses a software driver instead

of using your machines video hardware.

http://support.apple.com/kb/ht1455

My Late 2013 21.5inch Mac had been running slow over the last 6 months (frequent beach ball). I don't have automatic updates switched on, but overnight on Sep 25th, my Mac updated to Safari 14 and then everything went super slow and got even slower with Apps not loading and system monitor showing incredibly heavy disk usage.

Rebooted several times, but got even slower and finally (after 5 hours of trying different solutions) my Mac completely bricked and wouldn't get past the apple logo.

So, did a full recovery from my time Machine (shift R during boot and selected a backup prior to the update), with fingers crossed as I hadn't done this before.

Thirteen hours later ...... and my Mac is super fast and fully functioning.

First thing I did, was turned off automatic updates, as I don't want to be stressed out again.

Some oddities during the recovery ...

• my Photos library had to be repaired, which was done automatically
• my emails had to be converted to the 'New' Mail software (according to Apple) !! - they are all there.
• some old recurring events ended up in my Calendar, but these have since removed themselves automatically !!

Conclusion - Apple don't test their MacOS updates on old machines.

Welcome to the club. The update took out my 2015 Macbook Pro. I hope yours is recoverable, mine isn't. All manor of troubleshooting, down to power manager reset, SSD format and clean install still leaves me with kernel task eating 600% and more, with the fans going nuts with both Mojave and Catalina.

I'm having the same problem. I allowed the update last night and today my system is crippled in so many ways. It's a miracle that I managed to get into this forum. Took a long time though. Some apps are running so slow as to be useless; some won't even open. Files I created yesterday and show on the Finder list (e.g., pdf), are not opening -- it says they don't exist. This is nuts. It's like the computer is drunk or on acid or something. I ran a diagnostic and it just ended with a green checkmark with no details.

Coincidentally I updated my IOS to 14.0.1 yesterday, it wouldn't sync my I phone so I was guided to download some software, the iPhone synced perfectly to my ITunes and now my Garage Band has been killed. It won't allow me to install Garage Band so I am stuck possibly with the only option of upgrading to Mojave 10.14 and get a more up to date version of Gargage Band. Why have Apple products gone so terribly wrong?

Thank you Starplot and also to the many here reading and helping. There is something definitely fishy and odd about this, your experience is pointing in the same direction more or less as my experience. I too am using 6.0.5 Garage Band, which has been very reliable and stable. The prospect of losing my own created sounds isn't one I wish to contemplate so yes Apple, bloody well get on and fix it!

This is going to sound strange, but my iMac is beginning to behave normally again. I have no idea why this is happening. It's been about 4 hours since I last rebooted. Apps are opening quickly. Pdf's are opening - until about 30 minutes ago I was getting "could not be opened because file does not exist" - now it does. Textedit opens as usual. Games open as usual. Multiple browsers open simultaneously. Two hours ago, all was NUTS. This is the weirdest update I've ever encountered. Maybe my computer is sobering up...? Maybe the system just needs LOTS of time to deal with the update.... As of now, it's running just as it did yesterday. Totally weird....

There must be something screwy in this last update... I had a similar experience.

I installed the update and immediately my 21.5" (late 2013) iMac became unusable (beach balling on every mouse click; my Time Machine backup disk showed NO backups had been made; EtreCheck showed MAJOR issues; etc., etc.)

I spent several hours running Apple H/W diagnostics, booted into Recovery Mode and ran Disk Utility on both my Macintosh HD and Time Machine backup disks;. No H/W errors or disk errors were reported.

I then used Recovery Mode to reinstall my last Time Machine backup image just before I installed the last Security Update, and now everything is operating normally again.

I have NO third party S/W installed on my iMac -- I have no idea why this particular update "bricked" my system.

Well, I spoke too soon. Booted up today and it's been 1 1/2 hour and I'm still waiting for it to open a single email. I'm here today on my phone (android).

What makes the system go bezirk is that it registers each keystroke and click: it just takes about 20 minutes to execute. So if I click too often on something because of no response, each click is cued up to bite me later. For example, a "force quit" that didn't seem to register ends up happening half-hour later. Then Safari suddenly opens (clicked that an hour earlier) . Apps are opening and closing, seemingly at will but it's just because it's SO FFING SLOW.

This is a 2016 system. My old 2007 Tiger iMac is still running beautifully. Instant response. The only reason I bought a new one is because of internet access. Old Safari won't work there anymore. Garageband is better on the 10.4 Tiger. New one is a joke.

Tiger was the best system Apple ever made. From that it's been downhill.