Trying to add a single file to an existing ISO I ran into a bit of hiccup I can't see through. Here it is:
Having never done it before but encouraged by reading the advice from this question: Add/Delete/Modify files within a Disk Image (.dmg)?
hdiutil convert -format UDRW -o EditableImage.dmg givenImage.ISO
and although it created a DMG that was was "mount-able" - I was not able to edit it in any way. Trying to run
hdiutil resize -size 400m EditableImage.dmg
gave me a failure with Resource temporarily unavailable. (I rebooted just to be sure there was nothing using it)
hdiutil imageinfo EditableImage.dmg
indicated it was of Format: UDRW
but I couldn't actually write to it.. and this led me to asking here the question: what am I doing wrong?
[Runnning Catalina on a less than 1 yr old Mac with all updates]