Since upgrading to Catalina 10.5.4 I have been getting Prohibited Sign pop up

Question

Since upgrading to Catalina 10.5.4 I have been getting Prohibited Sign pop up

I have recently upgraded to the latest Catalina 10.5.4 (and Supplemental Update) on my iMac

Yesterday I was greeted with a Blank Screen and the "Prohibited" Symbol

Subsequently restarted my machine (Command-R) in Recovery Mode and ran a disk check

No errors - continued the boot process and system came back up but was running slow

Did observe in the Finder Window that the Sidebar preferences were not showing correctly (unable to see my Home User folder).

In the end I resorted to re-installing MacOS from Recovery Mode. At first it seemed to fix the issue but on coming back to my machine later - I was confronted by the Prohibition Symbol again! :(

Any ideas what might be corrupt ? Machine has been working fine for sometime

Many Thanks

iMac with Retina 5K display, macOS 10.15

Posted on May 4, 2020 1:01 AM

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Answer 1

Best reply

Barney-15E

Level 10

112,746 points

May 4, 2020 5:49 AM in response to bertie bassett

Have you read through this: If your Mac starts up to a circle with a line through it - Apple Support

It used to say something like "necessary boot files are missing," which indicated something entirely different that what it says, now. Because, as you are aware, the system booted just fine with that OS loaded.

If it keeps happening, I would suspect the drive might be failing. Eventually, the corruption causes the boot files to become unusable.

Open Disk Utility and check the SMART status of the drive. You have to select "Show All Devices" from the View popup menu button, then select the drive device (top, left outdented). The info pane will show the SMART status.

Note, however, that a "verified" status doesn't mean it is good to go. It just means it hasn't seen any odd behavior.

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Answer 2

Jayseph

Level 1

51 points

May 5, 2020 8:25 AM in response to bertie bassett

Hi there,

This is happening to a lot of machines - mine included - ever since the supplemental 10.15.4 update. My iMac is only a month old and I have the same issue: the prohibited sign when I restart my machine. After talking with Apple Support, I discovered that my iMac starts fine if all of my external drives are disconnected when starting up. I can then reattach them after start up and everything works fine.

Lots more discussion here with some ideas for resolution:

https://discussions.apple.com/thread/251259424

Hopefully there will be an update soon as this is a mess for a lot of people.

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Answer 3

May 5, 2020 7:57 AM in response to Barney-15E

Thanks for your reply

Yes I had read that document - I do get the same screen as referenced in that document - but my system boots up and then crashes out back to this screen.

I have run the Disk Utility a few times - the SMART status does show verified

I have subsequently run Etrecheck - and that indicates (what you suspected) that my disk might be failing. Probably just a coincidence that this happened shortly after upgrading to Catalina 10.5.4...

Regards

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Answer 4

May 5, 2020 8:41 AM in response to Jayseph

Thanks for sharing - It does seem that the Catalina 10.5.4 Supplemental Update is the culprit looking at the number of reports!

I was starting to think it was Malware! [Given the number of problems reported the supplemental update has achieved the same result!]

As you say hopefully there is a solution soon

Cheers

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Answer 5

Barney-15E

Level 10

112,746 points

May 5, 2020 9:07 AM in response to bertie bassett

I have run the Disk Utility a few times - the SMART status does show verified

I have subsequently run Etrecheck - and that indicates (what you suspected) that my disk might be failing. Probably just a coincidence that this happened shortly after upgrading to Catalina 10.5.4...

As I alluded, "verified" means nothing. I had a failing seagate drive years ago that didn't show anything but "verified" until it actually dropped dead.

Do have a spinning HDD or an SSD? I don't know what the MTBF for an SSD might be. I think they just decay as opposed to all out fail like a spinning HDD.

Not necessarily a coincidence, but maybe related. A failing drive will fail faster as it is written to significantly like when you update the OS.

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Answer 6

May 5, 2020 9:31 AM in response to Barney-15E

Etrecheck - just states that there is a "Failing hard drive - This machine has a hard drive that appears to be failing"

So it is not clear from the report whether it is SSD or HDD

But it may be a Red Herring!

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Answer 7

Barney-15E

Level 10

112,746 points

May 5, 2020 9:40 AM in response to bertie bassett

Being that it says it has a "failing hard drive" I would assume that it is the hard drive part of the Fusion Drive. Etresoft can probably weigh in on that if you sees this. But, the I/O errors that are registered might not be attributed to a particular drive in the Fuse. SSDs don't really fail that often, though I just found one of mine that has stopped working correctly. Seems like it has failed.

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