If I plug an external USB device (e.g., SD card, hard drive) into my
sleeping 2020 iMac, when it wakes up, the device is not recognized. I
have to unplug/re-plug it to show up.

Feature or bug?

--
Maybe I was raised wrong, but I was taught if you wanted something- you
worked for it.

On 2021-10-19 11:45, Wade Garrett wrote:
> If I plug an external USB device (e.g., SD card,  hard drive) into my
> sleeping 2020 iMac, when it wakes up, the device is not recognized. I
> have to unplug/re-plug it to show up.
>
> Feature or bug?

Neither? When the system wakes there is no 'event' to tell the OS that
something has happened on the USB subsystem.

That said, I don't know if it's different on this iMac or the Mini at
work. I'm going back there after lunch and I'll try to remember to
check it. Can't check it here presently.

--
"...there are many humorous things in this world; among them the white
man's notion that he is less savage than the other savages."
-Samuel Clemens

In message <skmp7p$f9o$1@dont-email.me> Wade Garrett <Wade@cooler.net> wrote:
> If I plug an external USB device (e.g., SD card, hard drive) into my
> sleeping 2020 iMac, when it wakes up, the device is not recognized. I
> have to unplug/re-plug it to show up.

> Feature or bug?

Feature. This is a security policy to prevent rogue USB devices from
hijacking your computer.

--
There used to be such simple directions, back in the days before they
invented parallel universes - Up and Down, Right and Left,
Backward and Forward, Past and Future... But normal directions
don't work in the multiverse, which has far too many dimensions
for anyone to find their way. So new ones have to be invented so
that the way can be found. Like: East of the Sun, West of the
Moon Or: Behind the North Wind. Or: At the Back of Beyond. Or:
There and Back Again. Or: Beyond the Fields We Know. --Lords and
Ladies

On 2021-10-19 15:45:59 +0000, Wade Garrett said:
>
> If I plug an external USB device (e.g., SD card, hard drive) into my
> sleeping 2020 iMac, when it wakes up, the device is not recognized. I
> have to unplug/re-plug it to show up.
>
> Feature or bug?

It's not just on waking either. It can also happen on booting.

I have two external hard drives plugged into my Mac, both of which are
recognised and appear on the desktop when the computer finishes
booting. When I plug in a USB keyring drive before booting or waking
the computer, that does not appear on the Desktop, and has to be
unplugged and plugged back in again.

I haven't ever bother to test it, but the only difference I can see is
that the hard drives are plugged directly into the computer, while the
USB keyring drive is plugged in via a USB hub ... but it's the same hub
used for the keyboard and mouse, which are recognised.

There's a similar weird issue with my USB printer. If I turn on the
printer after booting, the MacOS print window says it's not connected,
but will still actually print to and scan from it. If I turn the
printer off and on again, the MacOS can then see it. :-\

On 2021-10-19 11:45, Wade Garrett wrote:
> If I plug an external USB device (e.g., SD card, hard drive) into my
> sleeping 2020 iMac, when it wakes up, the device is not recognized. I
> have to unplug/re-plug it to show up.

At a lower level, this is handled by automount which itsel gets messages
from others like autofs etc. ( "man automount" from command line).
There are cases where the system itself will see the drives and mount
them, but Finder won't be aware of it.

When this happens, look at the /Volumes folder to see if the device was
in fact mounted even if Finder didn't put an icon on desktop of show it
in file selection dialogs.

( ls /Volumes from command line if Finder won't let you display the
contents).

While this is unlikely your case, one can disable automounting of
specific disk.

in /etc/autofs.conf , f you see a like such as:

UUID=FF9DBDC4-F77F-3F72-A6C2-26676F39B7CE none hfs rw,noauto

it means the disk with that UUID is not to be automounted. I am not
sure if there are GUI ways to do same and if such ways result in
autofs.conf to be updated. If you have no such lines in the file, than
you can rule out that specific keyring having been speficically
targetted to not be mounted.

At boot time, I have found some interesting behaviour with spinning
external drives. If I power up the mac and then the drive enclosure, the
mac would boot too quickly and not see the drives during initial scan of
buses etc and it wouldn't be until a munitor or two after booting that
the drives would appear. If I power the drive enclosure before powering
up the mac, then it sees all drives in it at boot and all is fine.

At boot time, the scanning is done by the EFI firmware, and that info is
handed over to the OS as it starts and automount doesn't kick in until
much later in boot process).

My speculation: if EFI doesn't understand a USB drive disk structure (or
your keychain behaves as a camera instead of a USB drive), it is quit
possible the OS wouldn't see that drive in the list of drives that EFI
provides the OS early on, and it wouldn't be seen until later when the
automount kicks in. Try to see why one USB devices mounts file at boot
and the other doesn't. What is different about them ? (use disk utility
to see how each is formatted, file system etc).

On 10/19/21 11:45 AM, Wade Garrett wrote:
> If I plug an external USB device (e.g., SD card,  hard drive) into my
> sleeping 2020 iMac, when it wakes up, the device is not recognized. I
> have to unplug/re-plug it to show up.
>
> Feature or bug?
>
Thanks, all, for the informative replies...

On Oct 19, 2021 at 5:09:27 PM PDT, "Your Name" <YourName@YourISP.com> wrote:

> On 2021-10-19 15:45:59 +0000, Wade Garrett said:
>>
>> If I plug an external USB device (e.g., SD card, hard drive) into my
>> sleeping 2020 iMac, when it wakes up, the device is not recognized. I
>> have to unplug/re-plug it to show up.
>>
>> Feature or bug?
>
> It's not just on waking either. It can also happen on booting.
>
> I have two external hard drives plugged into my Mac, both of which are
> recognised and appear on the desktop when the computer finishes
> booting. When I plug in a USB keyring drive before booting or waking
> the computer, that does not appear on the Desktop, and has to be
> unplugged and plugged back in again.
>
> I haven't ever bother to test it, but the only difference I can see is
> that the hard drives are plugged directly into the computer, while the
> USB keyring drive is plugged in via a USB hub ... but it's the same hub
> used for the keyboard and mouse, which are recognised.

I have three harddrive's plugged into a usb hub, which is then plugged into
the MacBook Pro (circa 2015). They never go unrecognized at boot-up or after
sleeping.

On 2021-10-22 00:41:40 +0000, gtr said:

> On Oct 19, 2021 at 5:09:27 PM PDT, "Your Name" <YourName@YourISP.com> wrote:
>
>> On 2021-10-19 15:45:59 +0000, Wade Garrett said:
>>>
>>> If I plug an external USB device (e.g., SD card, hard drive) into my
>>> sleeping 2020 iMac, when it wakes up, the device is not recognized. I
>>> have to unplug/re-plug it to show up.
>>>
>>> Feature or bug?
>>
>> It's not just on waking either. It can also happen on booting.
>>
>> I have two external hard drives plugged into my Mac, both of which are
>> recognised and appear on the desktop when the computer finishes
>> booting. When I plug in a USB keyring drive before booting or waking
>> the computer, that does not appear on the Desktop, and has to be
>> unplugged and plugged back in again.
>>
>> I haven't ever bother to test it, but the only difference I can see is
>> that the hard drives are plugged directly into the computer, while the
>> USB keyring drive is plugged in via a USB hub ... but it's the same hub
>> used for the keyboard and mouse, which are recognised.
>
> I have three harddrive's plugged into a usb hub, which is then plugged into
> the MacBook Pro (circa 2015). They never go unrecognized at boot-up or after
> sleeping.

The problem could actually be related to the version of USB the devices
have. Perhaps older versions of the USB standard are less
"handshakeable", for example. My USB sticks are certainly older than my
hard drives.