Making ISOs from DMG files

If you download a DMG file and need to write it to a CD or DVD but don’t have the necessary drive on your Mac, you can convert it to the Window’s friendly ISO format using the hdiutil command.

The hdiutil command is only available in Mac OSX so these steps must be performed on the Mac side, not on a Windows host.

Open a terminal window (Finder -> Applications -> Utilities -> Terminal)Given the disk image image.dmg in the current directory, it can be converted with:

hdiutil convert image.dmg -format UDTO -o image.iso

This will actually create a file called image.iso.cdr in the current directory (even though we asked for the output to be image.iso). This file can be safely renamed to image.iso, copied to a Windows server, and burned with your CD/DVD burner of choice.

Credit for this tip belongs to link