When I tried to download my first Mac app from the Internet (Google Earth), it got downloaded as DMG file. When I double clicked it, the file seemed to get mounted and a icon representing the contents showed up on my Desktop. I was able to open the icon and inside was an icon for Google Earth, which I could run. But after restarting the Mac, the icon representing the DMG file had disappeared from the desktop.
This app delivery format intrigued me and I also began wondering what is the correct way to use these applications and here is what I found out:
- The DMG files are similar to ISO disk images on Windows machines.
- Double clicking them automatically mounts them and adds a link to your desktop.
- The correct way to use them seems to be to mount the file and then move the contents to a location from where you can use them. (for example: in the case of Google Earth, I moved it into the Applications folder). Once you have moved the file into a permanent location, you can dismount the DMG file and even delete it.