Mount DMG Read Write

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Borrowed from MacEnterprise

One of the interesting things that can be done with hdiutil is attaching a read-only image using a shadow file. Here's how:

First, attach the read-only image as with the shadow option:

hdiutil attach -owners on your.dmg -shadow


After typing this command, the image will be attached as a new device to your operating system. Usually this is shown from the command line.

Next, copy over any items, or modify anything on the read-only image. Detach the image when finished by right clicking and ejecting it.


Now, convert the image back to read-only

hdiutil convert -format UDZO -o new.dmg your.dmg -shadow

You now have a brand new dmg, and the time and space required to convert the image to read-write has been eliminated.