Mac dmg no mountable file systems has become a problem for you. Dmg files are the installation files of any software on Mac, that means to install any software on Mac you need dmg file of it. The file is first mounted on a virtual disk and then you can extract the contents of it. So in case you are facing Mac dmg no mountable file systems issue then you will not be able to install that software. The problem mainly occurs if the dmg file is somehow corrupted, try to get a fresh copy of that file. You can either download it again or get a hard copy of it. If you are still getting Mac dmg no mountable file systems error then check by installing another dmg file, if the case is same, may be the problem is with the Mac OS X . You need to rectify using the disk utility which can deal with minor issues related to file system of Mac. Otherwise you have to format the drive and reinstall the OS again. Do not get worried about the lost data as you can get it with the time Machine backup. But if the backup is not there you can use Mac data recovery software. This is how you can fix Mac dmg no mountable file systems.