This question is for those of you familiar with command-line tools and disk images. I'm stumped!
Previously, I could mount a read-only disk image with a "shadow" file to make it read-write using this command:
hdiutil attach "someDiskImage.dmg" -shadow "someShadowFile.dmg"
However, on Catalina (macOS 10.15) this doesn't work. I'm not sure why or whether it is related to the OS version. Here is the output I get:
-> ls -al
total 391168
-rw-r--r--@ 1 myname admin 188484680 Nov 7 2018 example.dmg
-rw-r--r-- 1 myname admin 11767808 Nov 7 2018 example.dmg.shadow
-> hdiutil attach -shadow example.dmg.shadow example.dmg
Usage: hdiutil attach [options] <image>
hdiutil attach -help
->
Can anyone help me figure this out? Is -shadow just broken on Catalina? Thanks. Also, can you verify if you can reproduce this issue?
Best Answer
Alas, it seems that either macOS has changed the format of .shadow files in a breaking way, or that my .shadow files are corrupted (hundreds of them) without any corruption to the DMGs themselves (hundreds of them, all with checksums that match). I'm going to guess it's the first option. Nonetheless, the usage message only shows when mounting with these specific shadow files. When I create new shadow files, the disk images mount just fine.