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).