The DMG file extension is associated with disk images created for Mac OS X. The DMG format has replaced older disk image formats used with Mac OS 9 and earlier versions of the operating system.
DMG files are raw disk images that contain block data and may have one or two additional layers applied to add encryption and compression. These layers are identified in the hdiutil command line as "CEncryptedEncoding" and "CUDIFEncoding". DMG files are mostly used as software installers for the Mac OS platform.
How to open DMG Files
When opened in Mac OS the Disk Image is mounted as a volume that can be accessed within the Finder. The DMG file format was developed by Apple specifically for their Mac OS platform.
DMG files are not intended to be used with Microsoft Windows or any other Operating System. However, there are programs that can be used to open and convert some DMG files to an extension that is usable with Microsoft Windows or Linux.