A DMG Installer is convenient way to provide end-users a simple way to install an application bundle. They are basically a folder with a shortcut to the Applications directory but they can be customized with icons, backgrounds, and layout properties. A DMG file (.dmg) is a Mac OS X Disk Image file and it is used to package files or folders providing compression, encryption, and read-only to the package.
##Creating the DMG file
#Disk Utility
Type Disk Utility into Spotlite CMD+SPACEBAR from Finder
or from Terminal:
open /Applications/Utilities/Disk\ Utility.app/
File -> New -> Disk Image from Folder or CMD+SHIFT+N
Select the folder myapp.app/ when prompted then click Image.
In the Save As field enter a name for the file like myapp.dmg.
From the Image Format drop-down select read/write then click Save.
#Edit Folder Preferences Mount the dmg and open it by double-clicking the file in Finder or from Terminal:
open myapp.dmg
open /Volumes/myapp/
Create a link/shortcut to /Applications folder by right-clicking
on the Applications folder and selecting Make Alias then drag it into
the dmg folder or from Terminal:
cd /Volumes/myapp/
ln -s /Applications Applications
In Finder press CMD+1 to switch to icon view and arrange icons as needed.
Press CMD+J to show the View Options window and adjust view settings as needed.
From Background: section choose Picture then
Drag and drop the image you want to use as the
background where it says Drag image here.
Unmount/Eject the dmg when finished with View Options or from Terminal:
umount /Volumes/myapp/
#Compress and convert to Read-only
From Disk Utility right-click on myapp.dmg disk image and
select Convert "myapp.dmg".
In the Save As field enter a new name for the file like myappfinal.dmg.
From the Image Formate drop-down select read-only then click Save
or from Terminal:
hdiutil convert -format UDZO -o myappfinal.dmg myapp.dmg
#FIN Congratulations you are finished! Mount the new dmg to verify it is working properly.
Hope this helps!