Problem with MacOS update 10.15.7 2020-001

Oh, I think I understand. So basically there was a new boot option (what you are referring to as File System) when pressing Alt. I think that means the mac boot just got confused, and paused the continuation of the update by booting into the internal disk. So the update never got a chance to be applied at restart. Then, you went directly to the external disk, ending up with a non-updated macOS. The update boot option is temporarily created when applying an update - I guess Apple Developers know this stuff better obviously.

Some really complex stuff! :) Glad you were able to fix it!

Cheers, Jack

Same here.

I have been using a Samsung T5 external SSD successfully for a few months now and what a difference it has made to the speed of my late 2013 27” iMac. From hitting return on my user password it takes 3, yes 3 seconds to finish booting.

Since the 10.15.7 update a few days ago it will not boot from the external drive. I can view the external drive in finder, I can select it as a startup disk in system preferences, System Preferences tells me I have selected it but it boots from the internal hard drive. And it’s so slow!

When I hold the Option key down at startup the external drive is not listed. Only the Macintosh HD. It’s like the startup sequence waits for a while, can’t find something on the external drive, the says oh well I’ll use the hard drive to startup.

Yes, if there was only a way to install the Security Update 2020-1 WITHOUT requiring a restart.

As my system is configured now (external USB SSD with macOS 10.15.7 w/o Security Update 2020-1), the system behaves as expected.

However, when attempting to install the Security Update to my external USB SSD, the problem returns -- it simply will not boot up with the external drive, and defaults to my internal HD (macOS Mojave).

do not use Catalina but if you have already you must keep using the beta version as its the only one that can run diagnostic tools and read other file formats, this is because Mojave was not APFS and those versions of Catalina where able to convert prior formats to APFS using volumes or partitions of drives, now they are written for drives soldered on motherboards using only APFS, if you try adding anything the system will assume your modifying the computer Apple sold you and there for brick it., bricking the HD soldered on your motherboard means your mother board but on ext drives its tricky.

Example, failed Catalina installs on drives will still contain the data, only EFI diagnostics will not see the files, I tested this myself, I upgraded to the latest Catalina on a ext SSD, everything looked fine until I rebooted, once this took place I was left with no choice but access to the system of my internal HD, a 250GB SSD that came with the MacBook Pro signed certificate to that machine (you see even the parts are linked to the machine, changing anything means its bricked) anyway after I restarted the external SSD was empty!, nothing, a 512GB drive with my oder version of Catalina gong!,

6 months later I decided to see if I can get this external SSD to work with my iPad Pro using a camera adapter, and it did, but still refused to show any files on the Mac, so I backed up everything on my iPad Pro which has 512gb, tried re installing Catalina from a download I had since Mojave (older version) and it worked again! the files re appeared...

so anyone telling you that you have to reformat the drive is wrong, the files are there, Apple knows it, their techs know it, other critics of Apple also know it but they all want you to buy a new drive and spend days trying to recover files or replace everything, but it was clear in writing, Apple will not support older machines because of the component strategy, what's wrong is apple has not made it publicly clear which version of Catalina do or dont support certain machines but this is solved now with their latest greatest.

So your probably wondering if you should return to Mojave, its a good idea, only sad part is not having the features of notes and reminders or newer apps., it maybe worth it if it works for you, that is if you can deep format your drive, reset the pram and also leave your computer off and unplugged for 15 minutes, if you succeed its probably the best, other wise buy a new Mac...

im avoiding security update 2020-001 10.15.7, I some how succeeded in installing the latest update of Catalina on a MacBook Pro 2012, sadly it has issues with spitting off any external ssd I try installing Catalina on (partition or volumes), the issue causing all this is linked to EFI https://www.macobserver.com/news/macs-efi-might-outdated/ apple will not support older machines and this only comes with the OS now.

The Standalone Catalina Security Update 2020-01 is available now. May want to manually download attach the External Dive and execute the update pointing it to external drive for installation. See what happens.

I have successfully sorted this problem out but not sure how I did it. I took all my USB externalHard drives out and working successfully with all the updates done. The only external hard drive I left plugged in was my Samsung 2 TB SSD

I too have had this issue on my iMac with external SSD boot drive, as soon as I hit update I knew something wasn't right, I haven't necessarily fixed the problem but I have an acceptable work around thanks to the comments on here. Even though I have now manually installed the update it hasn't changed the issue for me at least, Seems it now doesn't like more than one external drive attached direct to USB in the back to the machine. So like me if you have an external boot drive and an External drive for Time machine as long as you only have one plugged direct in the machine and the other via a USB hub it works. I can now get in to recovery console etc that I couldn't before. So I am just debating whether to now recover from a back up and reinstall the OS to before I performed the update or just leave as it is now I've finally got it working again.

I have a MacBook Pro (Retina, 15-inch, Mid 2014) running 10.15.7 on an SDHD in the slot.

I PREFER to leave the internal SSD clean from the more and more unreliable new OS's, and install any new on SDHDs and let the cards be boot up only.

It has a fast bus (  Link Speed: 5.0 GT/s) yet using my Samsung 1T SSD through the thunderbolt connect is faster (  Speed: Up to 20 Gb/s x1) , (EDIT: I am keeping the external SSD Sammy on 10.13, it works and don't want to RUIN IT with some dumb update or upgrade). Im sure that's the card makers hyped specs not the Apple bus fault

Anyway, this new Sec Update was attempted to be done through System Prefs and allegedly got installed, eventually, don't remember how long but an hour or two to do...

After a couple boots and installs typical for the process, it loads the Apple logo but the 'progress thermometer' that should be showing never appears... half an hour of only the white Apple on black background.

I left it and went for a long walk, still nothing when I got back.

So I had to reinstall OS from internet recovery and would have thought that would inc. ALL the updates inc Sec but didn't.

So will be trying the download manually and install manually in a few moments...

I didn't want or expect this all to take a day or two yet here I am...

Is it worth it? Apple EFI missing can only assure there is no upgrade path, your basically forced to buy a new machine because eventually a single missing Catalina update will prevent a number of your Catalina compatible apps to NOT WORK or NOT WORK PROPERLY, especially drivers for 3rd party devices, accessories etc., and 75% of Catalina updates on Macs that shipped with out Catalina fail.

Now if you like spending days to only find out your os is not invesebly encrypted, the power is lowered to 5v and your MacBook Pro, iMacs etc won't boot unless you erase your whole SSD drive every other week then be my guest, other then that its contacting Apple about it because its in their ball park to decide if they should support your machine or not.

Well I have a late 2013 20” iMac which had El Capitan on it’s original drive and Catalina running on an external Samsung T5. Been using it like that since May 2019 and it worked a treat.

Did the security update this morning and my iMac booted up in El Capitan which I didn’t notice at first... Then to my horror I realised what had happened. But the problem was compounded by the fact that my SSD hadn’t mounted. So I ran Disk Utility on it and it saw the drive but showed nothing on the drive.

I zapped the PRAM - no difference. Tried reinstalling the OS to see if it recognised the drive - no good.

So I am assuming that the data is on the drive but because I am using El Capitan to boot from it doesn't see the drive. So I am assuming that I have two options: update my internal drive to Catalina and restore my files from a back up or restore my backup to a new SSD.

This is ****** annoying and I think that Apple are trying to get people to buy new machines or just sloppy with their updates. Thing is if they are so keen on Big Sur why are they doing updates for Catalina anyway?

If I get my iMac back to normal I will not be putting any security fixes on it again!!!

But anyone got any ideas why my drive isn’t visible?

Well I got a replacement SSD drive Sunday and using my granddaughter's MacBook Air I restored my back-up of Catalina to the new SSD drive. It worked on the laptop but when I plugged it into my iMac it didn't see the drive at all…

So monday morning I tried once more using the option key to choose which boot drive and the restored/new drive appeared and everything is back to normal - hurrah!.

What is interesting is that the security update has disappeared and this back-up was done before the security update was applied. It also booted my iMac with several apps still open. So I am assuming that when I was originally doing the security update something crashed and wrecked my drive…

Happy Bunny now but very angry with Apple and their crappy security update. Not sure that it has been applied or not??? I will write to them to find out more.

Suggest waiting a day or so for Apple to Post to the Download webpage then manually download. Once done, restart booting from External drive and apply the update.