[X-Unix] So what is a dmg file?

[Albert Lunde]

On Thu, Jan 22, 2004 at 08:12:09AM -0700, Doug McNutt wrote:
> .dmg  .smi   are two Apple disk image formats that are rather new.
> 
> How long will they be supported? Is it reasonable to use them for such things as archiving on a CD-ROM? Some of the older floppy image files that I once made can be unpacked only if I crank up my Mac IIFX for the job. Remember DropDisk?

In a related vein, are there cross-platform archive formats that support
Unicode file names and deep tree structures?

The leading contenders for broad support might seem to be .tar, .zip,
and .iso CD image files, but all those specs are showing their
age.  I've made Apple/Joliet/Rock Ridge ISO images with mkisofs 
and burned them to CDs and DVDs, but depending on what options
on chooses there are lots of warnings in the man page about
spec violations. On the PC side, Roxio's Easy CD Creator, balks
at burning deep directory trees, which Toast on the Mac will
burn without complaint. And my system at work was forced to a PC
I discovered a bunch of gotchas with respect to file/directory
names which made files unreadable on a PC.

So I'm kind of concerned about creating archives I'll be unable
to read on some future platform.