Combining multiple small DMGs into one large "virtual" DMG I created 50 small (1GB) encrypted DMGs using DiskUtility, and want to 
combine them into a single 50GB "virtual" drive but still have 50 1G 
images on disk. How? Why: 


I want to encrypt my files (even the filenames) before backing 
them up without using half my disk space just for encrypted files. 
I use an external backup service that'll backup 1G disk images
(files), but not 50G files. The smaller the individual disk images, 
the better. 
I'm running Mac OS X 10.4.11, so I can't use cryptomfs (plus, I'm 
not sure if cryptomfs creates several small files or one large 
file). I have MacFUSE installed, so I tried installing cryptomfs anyway,
but it failed (both 1.0 DMG and 1.1 pkg file). 
Since upgrading is neither free nor easy, I'd prefer to avoid it. 
I've considered other options (eg, a directory of hard links to 
the files with encrypted names for the hard links and relying on my 
backup service for content encryption), but they get fairly complex.
If you are on Leopard (OS X 10.5 or above) you can do this by having one encrypted disk image containing all the files.

The dmg to create in DiskUtility is a sparsebundle. This creates one bundle that mounts as a disk to OSX but actually is a directory and all the files in it are of a much smaller size. In Finder select the sparsesbundle and then Show Package Contents.

I just created a sparsebundle of capacity 1TB and copyied a 400GB vieo file onto it. The structure of the bindle had many files none of which were above 9MB

The band size can be controlled see hdiutil. But I have not done or worked out how do do this.