(powerbook G4 10.2.8) it appears my DiskImageMounter.app has gone missing, i have been informed that this is near impossible to delete. It should be locted in the core services file and it does not appear there?!?! Without this i am unable to download anything with the extension.dmg. Close the DiskImageMounter window, right-click the Windows 10 ISO file, and select Eject. Right-click on the install.wim file that you copied onto your Desktop and select Get Info. Go to Name & Extension and change the name of the file to Install.esd. Open the new folder on your Desktop where you copied the contents of the Windows 11 ISO file. Is normally found in the Utilities Folder/which is in applications right? And does the computer,that I copy off of, have to be the exact version as mine which is btw MAC OSX 10.2. Big Sur DiskImageMounter.app weirdness with network read/write.dmg 4 posts oldseeker. Wise, Aged Ars Veteran et Subscriptor. Registered: Jan 17, 2008. Posted: Sat May 08, 2021 5:44 pm.

1. Diskimagemounter Utility
2. Diskimagemounter Mac
3. Diskimagemounter Windows

I have an Airport Extreme with a USB port that's my home router and WiFi. My Mac is normally connected by Ethernet. I put an older 8GB flash drive in the Airport USB port, which I use as a cache backup for small high-value data so I can make a quick copy off-Mac without spinning up my usual backup disk (USB on my Mac). I also like that it's nearly hidden, in another room.
The flash drive has only two files: An encrypted .dmg, created read/write, 200 MB, and a readme file. When I want to do this quicky backup, I use Finder to mount the flash drive (a few seconds, the password is in my Keychain) and then mount the .dmg, maybe a little longer (The .dmg password is also in my Keychain). Then copy the data of interest to the .dmg, maybe delete something older, eject the .dmg, and then eject the flash drive. This has worked reliably since 2013, predating my current Airport installed in 2018.
Since upgrading to Big Sur (I waited until 11.2) the .dmg mount using either double-click, invoking DiskImageMounter.app, or choosing it from the context menu, fails. There's a progress popup 'Verifying AirPortDisk.dmg ...' which consistently fails after a few seconds with a popup “AirPortDisk.dmg” is damaged and can’t be opened. You should eject the disk.'. That has a '?' button, and clicking that tells me 'The app has been modified or damaged. The app has been modified, and its code does not match the original signed code. The app may be broken or corrupted, or it may have been tampered with. ...' along with some other irrelevant noise about security preferences that I could not relate to this context.
If I plug the flash drive into a USB hub connected to my Mac, DiskImageMounter.app mounts the .dmg without a problem.
If I use Finder to simply copy the .dmg from the Airport-mounted flash drive to the Desktop, then double-click on the copy, DiskImageMounter.app mounts it successfully.
Search found me the Terminal commands:

Diskimagemounter Utility

This mounts the .dmg directly from the Airport flash drive without complaint.
I looked at the man page for hdiutil to see if I would learn something, and found this under the 'verify' verb:

Diskimagemounter Mac

'... Read/write images don't contain checksums and thus can't be verified. ...', and sure enough,

Diskimagemounter Windows

I don't have any other NAS, so I can't tell if this is just Airport disk or a more general problem. So it seems to be some confused attempt to check a (nonexistent by design) signed code signature on my read/write data file .dmg, that only is incorrectly invoked using the GUI, and only on a network-mounted volume. But I don't know enough about whatever they did in Big Sur that's responsible, or more importantly, how to fix it. There are workarounds, but they are awkward, and this used to work.
I couldn't find anything related to this issue with internet search. Any idea from the community?