Problem with MacOS update 10.15.7 2020-001

No *real* answer here, just joining in with the problem. I got a similar setup (imac 2013 with external SSD it starts from) and got big problems with the security update, including a non-starting system sometimes, while it sometimes works. I tried too many things to recap here, what *seems* to improve the situation for me was to plug the SSD (Samsung T5 in my case) to an USB3-hub with it's own power supply. It *seems* something with USB changed and somehow when starting up the external SSD is not ready to do it's job. It's all wild guesses, I'm no real expert, but as there are not a lot of reports about the problem I thought I share it here. Hopefully someone comes with a proper explanation and fix.

I am having the same issue. Late 2013 iMac with Startup Disk running on an external SSD. After updating the system boots from original internal HDD which has macOS 10.12.3 installed. System will not recognize the external SSD which is now running macOS 10.15.7.

I have two external HDDs plugged into the iMac, and the system does recognize these HDDs.

After many unsuccessful reboots, I shut it down and then unplugged the two external HDDs and left the external SSD boot drive plugged in. This allowed me to boot as normal. Then I shut it down again, plugged the external HDDs back in, and the problem is back.

Argh.

There are many reasons an external drive will not boot a computer, or will stop booting. Too many to detail in a short reply to your post, but I suggest that you read this https://bombich.com/kb/ccc5/help-my-clone-wont-boot and work through the possibilities. Whether you are using CCC or not, it describes multiple reasons a clone will not boot or will stop booting computers of different vintages.

Hi GazzaMataz, fair enough you were able to revive your iMac. Could you provide more details? Model/Build year, and some more config maybe? As I think, fototypo is on the right track with the build year of the Mac, or maybe even closer with classical HD and/or Boot Rom.

Second oint: Did you check your USB port speed after having reconnected all you external disks? As I wrote above, I suffered heavy drops down to transfer rates of some 20 MB/s instead of the usual ~420 on my SSD drives (and on HDDs, too, so whole USB Bus was slow, only startup volume port ran at normal speed). You might check this with "Blackmagic Disk Speed Test", free tool and uncritical to install.

For now it seems to be the only option to disconnect all other drives on start / Restart. Not very comfortable, but anyway something that seems to work...

@fototypo: That's interesting. Which System is installed internally? And which kind of FS is it running there? In my case I had Catalina 10.5.7. on the internal, too, so the internal HD Filesystem was converted to APFS when updating (switched to external SDD later then). This might be another issue, in meaning of updater thinking: "If I find another Catalina oder APFS volume internally, bah – I PREFER THIS ONE MORE – ;-)

Hi fototype (and anyone else)

I send this as a bug report to Apple again. I'd kindly ask everyone with the same or similar issue(s) to do the same (as logically the support and developer team does not automatically follow the threads here in this forum)

https://www.apple.com/feedback/macos.html

Takes you 3 minutes of your lifetime, and hopefully heals you from daily morning-gym unplugging and replugging devices ;-)

Cheers and stay tuned,

Phil

Been there done that, waste of time, this problem IMHO is a clear agenda by Apple to remove older iMac's from our desktops. Only solution is to get a iFixit kit and replace the the HDD with an SSD. That is my low cost solution and my iMac 14,2 is functioning like a whole new iMac. The 14,2 will stay on my desktop till the software catches up to the new M1 architecture, no boot camp for me.

I came here before after my macbook pro int ssd would not boot and refused to erase and re install when it was the correct advise from the get go and believe me i had conspiracy theories lol 😂

well. Its like this, use time machine or ccc to clone whatever, always use ext ssd or hd for your projects, icloud is enough to save everything else unless your downloading tons of videos or large files to your desktop and adding this to icloud,

anything goes wrong you can always boot in recover (command + r) then disable system integrity to reboot in-safe mode but even this was a waste of time for me, as soon as i wiped the internal drive , re installed catalina and let my user sync from icloud all was fine...i had issues installing catalina on a ex ssd, wasted a week trying to solve this thinking if i installed it to the int ssd my data will be wiped, after i decided to just start clean i realized catalina kept my data on a separate volume apart from the system...

so the whole time i was going through this for over a week i tried finding out what it was etc and i found nothing but conspiracy theories about why it happened, its true users where about all this when they upgraded to catalina because the early beta was working side by side with 32bit apps...no one even suggested it...

so start over clean, figure out which version runs best and download it, you wont regret it, until you want a new app that is not compatible and buy a new machine.

I just read the boot ROM is also updated by this update. (But it's possible I misunderstood.) Could be some issue there? Apparently it's nothing a normal user can fix, I guess?!?

My setup is like this: The internal (rotational) HD is a clone of the startup-external-ssd. It really seems the update screwed up those two installations. Somehow while installation the custom startup-volume is forgotten ... or it is not recognized during start up at all.

To be honest I think they really don't test setups like the ones we use. Unfortunately. But I hope I'm wrong.

;-)

There are more and more similar reports coming up here recently. I just tried but failed again to connect the ext SSD directly to the iMac, it won't boot. *somehow* it seems to depend on the actual USB port *and* the port the Timemachine-Drive is plugged to. But I'm to dumb to really figuring out how. Sometimes it also seem just completely erratic whether it works or not, to be honest.

Definitely installed that 2020-001 Security Update for both machines running 10.15.7. It is installed on both the internal SSD as well as various external drives (which include both Samsung SSDs; and WD Passport, Apricorn Fortress, and Toshiba HDs) that can boot these computers. But they are not as old as yours -- the ones I use are 2017 (work) and 2019 (personal). So you have different circumstances in that respect.

I found this article https://bombich.com/kb/ccc5/help-my-clone-wont-boot informative. While it pertains to bootable clones, it describes a remarkable long list of reasons why external bootable drives sometimes fail to boot various Mac computers.

Well I managed to reformat my old Samsung T5 SSD which had my original Catalina installation and I decided to use this as a second back-up. So I now had two back-up drives and a boot drive hanging out the back of my iMac (14,3) which ran fine - until I booted up this morning…

It booted straight into El Capitan and when I rebooted using the option key it didn't see any external drives. So I unplugged all the external drives except my boot drive and rebooted with the option key held down. Then I could see my Catalina drive and it booted into that. So I then plugged my other two drives in. So it seems that although I never installed the security update I am now experiencing the same problem that you chaps have in that it doesn't seem to like more than one external drive plugged in at a time whilst booting.

I have spoke to Apple about this using a UK e-mail but they simply told me to talk to Apple Care or book an appointment with an Apple Genius. That will be impossible under the current lock-down and I doubt Apple Care will help unless I took out an extended warranty. I need to look up this EFI stuff…

Turns more and more out, that the issue is about models before or equal to the iMac late 2013, as an example. The difference to the upcoming 2014 generation (among other stuff) is the use of Fusion Drives / SSD, which were introduced on iMac first time with the iMac Late 2014

Let's see if someone with a mid 2014 21,5 iMac (which used still some HDD internal on default, although configurable with Fusion or SSD only) experiencing the same issue, and on the other hand users with newer iMacs using Fusion / SSD internally donÄt have any problems with this update.

As soon as we got more, I'll update my thread in the developer forum.

Meanwhile cheers and enjoy some sporty restarts with crawling around the desk ;-)

Both CCC and SuperDuper are routinely (currently) creating bootable external drives for both new and old Macs. I'm using them myself, with Catalina, and CCC even provides instructions for creating bootable external Big Sur drives (both companies are still working on a cloning technique that does not require the CCC instructions and extra steps below). TechTool Pro also includes a cloning tool that Micromat says can create a bootable clone.

It is common for users to switch to these external bootable drive clones when they have a problem with their internal drives. I've done it and my computer was not bricked.

There are MANY reasons external clones won't boot:

https://bombich.com/kb/ccc4/help-my-clone-wont-boot

Here is the procedure to create a bootable clone under Big Sur:

https://bombich.com/blog/2020/11/03/yes-you-can-have-bootable-backups-on-macos-big-sur

I haven't checked if it makes bootable clones under Catalina, but Apple's Disk Utility also provides a Restore function that supposedly clones an existing drive. It used to work with earlier MacOS, maybe it doesn't work any more.

For what it's worth, Dave Nanian, the creator and owner of SuperDuper was sent this entire thread and asked if he has seen these sorts of problems with external drives booting older Macs. His answer was basically "no" but he also had some other comments ... He makes his livelihood with bootable external devices so I figured if anyone knows what might be causing this, he would ...

https://www.shirt-pocket.com/forums/showthread.php?t=7261