Re: using dmg files (fwd)

[Markus Hitter]

Am 24.09.2004 um 10:30 schrieb Richard Frith-Macdonald:

> On 24 Sep 2004, at 09:26, Alex Perez wrote:
>
> > Rogelio Serrano wrote:
> >
> > > I wonder why apple uses that format. Can we do something
> > > similar like using iso or cramfs format instead? So we can loop 
> > > mount the
> > > image then drag and drop to the Apps directory or wherever?
> > we could but there's no point
>
> Yes, I can't see what the advantage of using a disk image would be...

You can mount the image and run the app directly off the compressed 
"archive", without touching the disk. Mac OS allows to mount volumes 
(images, removable disks) as an average user: just double click the 
image. Very handy and very fast if you want to try out a package.

Very handy if you have to deal with self-modifying apps. Shadow-mount 
the image and there you go. All changes go into the shadow file while 
the distributed image its self isn't modified. This enables you to put 
such apps on read-only volumes.

Apple's .dmg format even allows to distribute a small image and when 
mounting the image, the system will automatically download the 
remaining part from the net. Many users don't like such "automatic" net 
access, however.

> You could mount it and then copy the contents out of it, but I don't 
> see
> how that would be any better than having a .tar.gz file which you could
> unarchive directly to where you want it.

A .tar.gz file requires you to fiddle with the command line. Something 
John Doe's grandma and even the average computer user isn't very savy 
on.


Am 24.09.2004 um 09:12 schrieb Rogelio Serrano:

> Can we do something similar like using iso format instead?

Partially, yes. Don't know how many UNIX-like OS's allow mounting 
volumes in user space. Plus, iso images can't be compressed internally. 
Dunno about cramfs.


This all requires a self containing app, of course. If you want your OS 
X app to be a success, you better package it this way.


HTH,
Markus

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Dipl. Ing. Markus Hitter
http://www.jump-ing.de/