Problem with MacOS update 10.15.7 2020-001

Also had issues with this 10.15.7 2020-001 update. Here is what worked running an Imac 2013 from external SSD.

• When starting the update, still on black screen, it had a brief reboot.
• After that the Mac failed to load from SSD every time.
• As my internal drive is a clone the Mac was only starting up with the internal disk, and not recognising the SSD as target disk.
• Pressing option key wasn't working to select SSD disk.

What worked for me:

1. I unplugged everything connected to the Mac and plugged my SSD in a different USB (the closest to the edge)
2. Did a PRAM reset (once)
3. Switched on, loud startup sound and the Mac loaded my internal drive with the clone, then I shut down after loading
4. Switched on again and pressed option key (the SSD disk appeared)
5. After loading the SSD I noticed the update was still pending on Systems Pref
6. Shut down again
7. Switched on again to check it would load from SSD, and it did!
8. Performed the update with no problem after that

Hope this helps..

Hi ElkyOne,

I've also been experiencing this problem and reporting via these forums. Here is my configuration:

Late 2013 21.5"  iMac14,1 Quad-Core Intel Core i5 2.7 GHz. Internal HD is configured with Mojave (all updates).

External USB devices: 1TB OWC Envoy Pro EX (NVMe M.2) SSD with Catalina 10.15.7, WD MyBook (TimeMachine), Apple SuperDrive (when needed), and my UPS is also connected via USB.

When I had attempted to install the 2020-001 Security Update, my iMac failed to recognize my SSD upon restart -- it appears that the update was never applied. My iMac had restarted from the internal HD.

In order to get booted up again, I had to do the following:

1. disconnect all USB devices
2. connect my SSD to the first USB port (next to the Thunderbolt ports)
3. reset NVRAM (three "chimes" -- don't know if this was necessary, but I did it as a precaution)
4. thought about an SMC reset, but I did not (sometimes needed to reset USB power, etc.)
5. reconnected remaining USB devices

Been running normally from the SSD (w/o 2020-001 SU) as I was prior to attempting the update.

In my case, I had to disconnect all USB-related devices, except for my SSD w/ Catalina on it, moved my SSD to the 1st USB port (next to the Thunderbolt ports on my iMac), reset the NVRAM, and finally I was able to successful boot up.

Another forum member mentioned that it could be some sort of timing issue associated with 10.15.7 and the USB devices.

Having done the new Catalina security update on my late 2013 iMac and noting that I can no longer boot from the external HD running Catalina, I searched the internet and found many, many things to try. After reformatting the external with High Sierra (none of the other multiple Macs here run anything higher than High Sierra)—and thinking that this was a problem with my external until all the reports of issues started coming in—NVRAM resets, selecting the external HD as the startup drive and multiple others, I tried all, varied all and this is what seemed to have worked for me.

Computer was shut down.

All USB devices were unplugged.

Turned on computer and immediately after the bong, held down the OPTION key. My internal HD came up as the only startup  choice. 

At this point, I replugged my external into the USB slot closest to the FireWire port. This was mentioned somewhere on the net as critical to this adventure. My external then showed up as another startup choice. Using the tab key on my Apple wireless keyboard, I was able to select the external HD.

External booted the computer. I was then able to upgrade to Catalina from High Sierra by using a previously made USB bootable Catalina system disk. Completed the Catalina install, DID NOT do the security update, then shut down and restarted the computer. Rebooted each time from the external drive...no special key presses. Ahhh....now to reload all my programs and data onto the external.

This is part of what finally after 1,5 days trying everything saved me, too.

1. Deleted the system part of my SSD (so not the "xyz-data" volume, just the system volume
2. Installed disconnected everything else from USB, only leaving this SSD plugged, as said to the 1st port of my iMac close to the thunderbolts (or called 4th or whatever you want)
3. Installation successful, so I re-connected other drives.
4. Then, after a next restart, problems seems to re-appear, booting from internal. Disconnected everything again, shut down
5. SMC Reset (unplug from power, in case of desktop machines)
6. NVRAM Reset (alt-cmd-p-r on immediately after powering on, hand keep them pressed together until your Mac really chimes and starts another time (yes, our fingers might hurt, get prepared)
7. To be safe and avoid one more time booting from internal, pressed alt after that, to call boot-manager
8. In Finder, reconnected drives again
9. What happened then to me: Only the first port with system SSD delivered the used speed. The other three port were ****** slow as a floppy disk (well, 20 MB/s, instead of 420-450 what I usually have on the other SSD or 15o on another 7200 HD)
10. Another restart, again, disconnecting all, and again resetting NVRAM
11. Now it's working, usb bus port speed seems to be fine again (checking now the last drive, my Time Machine Drive, which I can't check with Blackmagic disc-tool, cause it's read only)

What I avoid until any further update about this update:

• No Shut-Down, setting my Mac to sleep instead
• Ignoring this security update (well, I don't like to ignore, but anyway, I won't ride this ****-trip again

See another post with my system specs for more:

https://discussions.apple.com/thread/252193478

I totally agree to you, and don't see no need for any conspiracy. It is a bug, that was concerning really special constellations. What I figured out, it seems more and more that following combination COULD lead to the described Problem

• iMac, late 2013
• Catalina 10.15.7 installed and running on external disk (Crucial X8 2B SSD). I had the same system on my internal original Mac HD
• Installing the security update 2020-001, with included Safari Updates
• And, I think, this is by hardware quite interesting: More that one external disk (or maybe other USB devices too, in my case it was both)
• Some SMC, NVRAM reset might help (I did it, but I've done so much in a row, that this is hard to be proven as necessary or binding)
• More interesting: Even with all other disks unplugged, the iMac only accepts the external volume connected to the first port, counting from right to left, so just beside the thunderbolts)
• The other USB ports suffered after successful booting significant drop of speed of speed, down to 15 MBs on SSD drives
• This might especially explain the Time Machine problem, described as being slow. Same for me, when ran migration tool, was wondering, but I found the problem Wirth the affected slow ports when trying to work in Logic, and my instruments were loading like time travel to Floppy Disks ;-) Of course, this does affect massively the Time Machine restore time. It really becomes a time-wasting-machine ;-)

So my personal opinion, why there are quite a lot users around suffering this problem, but not really thousands of them: iMac 27 late 2013 is not used that often anymore. So there are two user groups:

1.) The ones just using this "old" iMac for casual stuff, it is still running, and yes, it is a stable and lovely machine (I work professionally in graphic design, animation, till 3D, so everyday on S,AE, PP, AI, INDD and Blender / Cinema 4D (yes this is a pain in the a** concerning rending of course, but I have good deals with render farms, and always on my main clients side (an agency) a lot of other Macs, so sometimes we just let them all share rendering). I'm working a lot with Audio, too, right now on a classical composition using BBCSO from Spitfire Audio, with some 30 tracks Dorchester, some clips of course, but this iMac is still a lovely working horse. Sorry lost my track, back tip the users (you see, I really love my old iMac beside other ones haha)

These casual users might have (if they have) maybe one external disks, but I think quite few using this as a system disk. I run 2 SSDs, three HDDs and Midi/Music equipment. But this is NOT the normal user on an 6-8 year old machine I guess, nope?

And even if - maybe nothing would have happened if my external System SSD would have been on this USBN port when doing the security update. Who knows? I won't try it, go of course ;-)

I'm working on Mac since early mid 90ies, and I really don't see any sense in these ideas. Apple users will update their systems on their own, they don't need to be forced to do, usually once you have a Mac, you'll stay (special uses e.g. switching to a windows Machine for better graphic card support in 3D worlds is another topic)

So: NO, it is just bad luck, to have this special iMac with this kind of setup running this security update. And maybe it was a rainy day, or you ate too much garlic, before, **** who knows 🤣

In case of any more questions, please fell free to ask on, I'm always willing to help, like all others around here too.

Cheers and all the best, will go on composing a bit. On my loved old iMac, who's running pretty stable on this "****** Catalina" system (I had no a single prob with Catalina all the time, don't understand everyone complaining about "Crapalina". And again, I am a power user (oh yes, I had one problem, a "pirated" plug in didn't want to run with Catalina in Logic. I don't care, 'cause I was just waiting to buy it, and there was no demo version. I'm a bad guy, I know. But I bought it, as anyway planned, so I'm a nice guy again 😇

Stay tuned 🤘😎

Phil

After one unsuccessful attempt at resetting NVRAM via the Terminal, I did as CapsuleFab described and disconnected all peripherals from my iMac except the SSD. I managed to get three solid chimes during a keyboard NVRAM reset and booted up with my internal HD.

I reformatted my external USB SSD to HFS+ (journaled), GUID, downloaded a fresh Catalina installer, crossed my fingers, said a prayer, and launched the installer.

Everything went as before, but this time the iMac booted up and completed the installation. I just spent 60 minutes transferring files via Migration Assistant, held my breath during the reboot to complete the setup, and I now have Catalina successfully running again on my external SSD.

I immediately received a notice that there were updates to 10.15.7 and Safari, which I summarily ignored -- I simply don't want to go through this again.

I’ve had a similar problem after what must have been the same update (running Catalina on IMac 2013 external SSD) and driven me nuts trying to figure out what happened (wiped my external drive to start again only for it to no longer want to accept any install or boot to it). I removed all external drives, to get in to recovery mode, rebuilt my internal drive, had to create a new partition in my internal drive, install Catalina there also (just to prove it was a external drive issue). Then I could reinstall the OS to external SSD - the second internal install seems to have cleared/reset something. Hoping I can then recovery files from backup. 2.5 wasted days on this.... 🙄 I wondered why this suddenly happened.

A solution that work for me. 2013 iMac 14,2. My iMac hard been functioning perfectly, even with 10.15.6 installed, till the fateful day I updated to 10.15.7. My fix was to remove the original HDD, with my SSD. That however is not an option for all. My external SSD however ( Samsung T5 ) is still not usable as an external boot drive until I did the following.

1. Buckup the external SSD
2. Shutdown your Mac
3. Restart, Hold down the Command +R on startup till the Apple logo appears, release keys
4. One in recovery mode, select Disk Utility
5. In Dish Utility select your external SSD
6. Select erase
7. Give the Disk a name, format OSX Extended (Journaled), and GUID Partition Table
8. Select Security Options
9. Move slider from fastest on the left, 1 tick to the right, this will erase and do 1 pass of zeroes.
10. Once the format is complete. Restart and follow normal Mojave install process.,
11. Worked for me, after many, many other attempts to fix the Catalina bug.

Primarily booting from internal drive. However, also booting from external SSD attached to thunderbolt (USB C) port. Internal drive is original to the iMac. Internal drive is also a SSD. (Also have a second external SSD and external hard drive attached - not booting from those)

I did not say in the above post, but the specific problems encountered were:

Booting from the wrong drive, e.g., boot from external SSD although internal drive was specified as the boot drive.

Boot failure - the computer would not boot up and would have the prohibitive symbol (circle/slash). It would fail to boot about 1 in 4 times.

Just for more information, the following was done to solve the problem that did not work:

Reset SMC

Reset NVRAM

Cleared out old software on the internal drive (bits and pieces from previous installs)

Ran etrecheck to look for problems - none identified.

Perform first aid on the internal drive - no problems found.

Erased internal drive and reinstalled Catalina. (See next line)

Then what worked:

Erased internal drive and reinstalled Catalina a second time. Then reset NVRAM after reinstall.

That solved the problem. I have since booted up now about 15 times with no errors. From both the internal drive and external SSD. (And as stated above, the only difference now is 2020-001 is not installed along with 2 safari updates.)

If you are wondering, all of the boot ups have been to test the system to see of the problem is solved.

Thanks for posting this solution. Additionally I believed that Catalina left something on the external SSD, in my case a Samsung T5, that turned the SSD into a read-only drive, even post reformat. After many attempts I finally decided to go beyond the default format option in disk Utility . At startup press CMD+R hold till Apple Logo appears. Select “Disk Utility” from the OS X Utilities list. Click Continue. Select the disk ( External SSD) you’d like to erase by clicking on it in the sidebar. Click the Erase button. Now, Click the Security Options button. Here is where I found the solution that has worked for me. The Security Options window includes a slider that enables you to determine how thoroughly you want to erase your hard drive. Move the slider over 1 NOTCH to the RIGHT. Click OK. Then Click Erase, the more secure method you select, the longer it will take. Once complete you can clone your HDD to the External SSD. You should now be able to change the Startup Disk to the External SSD, and restart. This has worked for me and has been operating normally, including restarts and shutdowns.

Look here:

https://discussions.apple.com/thread/252178875

Someone had success after multiple (!) PRAM resets.

Just a note to my reply above....do not plug any other USB device in until the computer boots from your external HD, which I found worked when plugged into the USB port closest to the Firewire port. YMMV...but if it helps let us know.

The internal HD is a clone of the external, startup SSD. Both are APFS, yes. I don't know any more when it was, long prior to Catalina there was an update when even conventional HDs where converted to APFS. Could have been 2018? 2017? Until that 2020-001 update that was not a problem at all.

I'm no expert but thought the EFI/boot-rom is ALWAYS on the internal device, booting to the startup-volume is 2nd step. It *seems* the security update cannot handle it, if the startup-volume isn't on the same physical device, or at least there are issues.

Unfortunately I cannot remember what did the trick in my case, I think I installed the 2020-001 update directly to the internal HD at one point, and than at the external again, so I basically ran it twice; but I tried so many things, it could be it's just coincidence. Sorry, this is not very scientific, I know, I was just in panic to get that thing to work, trying all I knew at once ...

I have a 2017 iMacPro. Having major boot problems since installing the Catalina security update in December. After a lot of troubleshooting the following seems to have solved the problem (fingers crossed).

Used System Recovery - completely erased the internal drive and installed a fresh copy of Catalina. Note that the security patch 2020-001 does not install when this is done. Do not install the patch.

Started up computer & had same boot issue, but..... then reset NVRAM. After resetting NVRAM my boot issues have gone away. At least I think so. Have done 12 test boots with various attached drives and all have been successful.

So the sequence was to replace Catalina, (do not install the 2020-001 patch), then reset NVRAM. Will continue to monitor to verify this have finally fixed the issue.