What's up with all these disk images?

jove

Member
Hello,

Is there a reason why so much software comes as disk images? There are countless ways to package, compress, and build installers for software. The disk images always leave the mounted image that has to be thrown away. I have had many people from end-users to new-Mac-old-Windows-users ask me what to do with that left-over.

BTW - My instincts are to pronounce .dmg as "dot damage".
 

Matrix Agent

Masochist Mascot
I started a thread about this a little while back.

While i find disk images to be very convenient because they require no installation, just a drag and drop the app, many newbies will problably not understand that just mounting a disk image does not result in it becoming stored perminantly. In all probablility, once newbies beat the learning curve, they'll problably prefer then to a standard decompression-installation type procedure. Plus, disk images are endorsed by apple.


One problem: Aren't disk images usually bigger than standard compressed files? I wonder why so many are used for the net then, hmm...
 

Red Phoenix

Registered
I tried posting this a while ago, but Macosx.com went down, or something...

It's actually the way Apple is pushing developers to release their software. While I don't think it's any better than files that have been tarred and gzipped, it's certainly better than developers using the pkg format. At least when it's a disk image, the developer keeps the installation process simple (as in, drag the icon to the Applications folder), and hence the uninstallation process is just as simple (drag the icon to the trash). While disk image files are a little bit of a pain with having to "eject" the disk, I think Apple felt it was a small price to pay to avoid the installation mess that Windows has.

As for disk images being larger, I think it's kind of negligable (as in, I haven't paid close attention to the difference, and haven't noticed any big difference.) Besides, most places gzip the files. This seems kind of odd, though. Do dmg files not have any kind of compression like img files can? A developer for Apple at one point claimed that compression with img files was comparable to sit compression. Since making dmg's is a little clunkly still, I haven't checked to see if it's there.
 

knighthawk

Registered
I think one of the biggest problems with this format for developers is that it does not allow the developer the control over the user. Say for example, there is a demo application that expires in 30 days. Because the use just dragged it onto the hard drive, the preferences are stored only in that persons preference folder allowing a user to recreate the user and clear the preferences. If the installer requires the Admin password (which I don't think that .dmg methods allow this) it allows the developer to install the preferences in the main library instead.

From the stand-point of a computer admin, using the .dmg for applications does not allow me to prevent users from installing applications in their own home directory unless I made the DiskCopy utility unexecutable to the user.

Another funny thing that surprised me is that the .dmg files do not eject when you log out. Maybe there will be more options when Apple comes out with 10.1.
 

AdmiralAK

Simply Daemonic
I think that giving out software in .img or .dmg files is quite natural actually.

The reason is this:

Most software developers like M$, apple, Netscape also have their software available as CD-ROMs. Why not burn the CD-ROM first (which they probably do with their GMs of their software) and then just make the .dmg or .img file.



Admiral
 

jove

Member
Hello,

If the use of dmg files were more consistant and streamlined I wouldn't be so hesitant to use them myself. Unfortunately I have downloaded .dmg.sit.hqx files with installers in them!

I beleive the ideal is the simple package installer. The interface is simple and the developers can do logic invisible to the user. Remember most end-users do not want choice in the setup context. They want to be guided with simple instructions.

I solid system can handle when a user intentially or mistakenly exerts choice at unexpected times :) But that is another discussion entirely.
 

jove

Member
Hello,

The OS9 version of DiskCopy lets you create a .img from a folder. The X version does not have that option. Nor was I able to find any appropriate tool in the dev tools. The package maker is there.

Good question >-|
 

Matrix Agent

Masochist Mascot
Toast can create them, its about $50, well worth it any way you look at it.
 

jove

Member
Hello,

Search Results:
DMG Fixer 1.0  -  Fixes OS X .dmg files that show up as TEXT files 70k Freeware 05/02/2001 (Both X and 9)
DMG Maker 1.1.4  -  front end for creating disk images (.dmg or .img) 280k Freeware 07/16/2001 (Just X)

Ain't VersionTracker splendid!

And one of the reviews

Heh, nope you cant do this stuff in DiskCopy on OSX..That is sort of the problem...It can, however, be done using a the mac os x shell (hdiutil, hdid, newfs_hfs). There is a tutorial on stepwise on that. This is all in all a handy utility, but not essential.  
 

Red Phoenix

Registered
If I remember, one of the limitations with dmg files is that files with resource forks need not apply. This obviously makes them of limited use for OS 9 since practically everything has them. Anyway, that's why I'm not surprised that OS 9 has limited (if any) support for dmg files.
 

RacerX

Old Rhapsody User
I've been using standard disk images for quite some time for back-ups. Using the write-only form, you can make an image file of a 1Gb drive or folder that can fit on a CD (depending ob the types of files on the image). It's great, you put in a CD, mount the image on the CD and a read-only image appears that is larger than what could normally be pu on a CD. StuffIt is a good internet transfer format, but I usually send things as images that have been gnu-zips (that is they appears as "File.img.gz"). All of this stuff is free, so I don't see any reason to pay for StuffIt for this type of stuff.
 

RacerX

Old Rhapsody User
The addition of gzip to any other format makes it more internet friendly. Infact if you have problems openning a download that seem to be a tar file, you may want to try un-zipping it first and then try again (I have had the .gz extension dropped on files with long file names). I have seen many .dmg.gz files out there ever since the release of the final version of Mac OS X. It was strange downloading things that I have been using for years that have always been in the .tar.gz form, and now they are almost all .dmg.gz (though OpenUp is still a must on OPENSTEP/Rhapsody/Mac OS X Server 1.x systems).

I seem to remember hearing that gzip is a text based document format the same way that bin and hqx are. Image and installer files would have the problem of having there resource forks removed or changed to text docs making them unusable (though you could try fixing them with ResEdit). That at least was my understanding of it.
 

AdmiralAK

Simply Daemonic
That;s happened to me with newton packages.
IF you download a newton package (unzipped) it is treated by the newton connection utils as a non-entity so I;ve spent a lot of time in res edit changing creator types and file types lol :p

is there an OS X equivilent of are file/creator types obsolete ?


Admiral
 

RacerX

Old Rhapsody User
Actually in 10.1 if you give a file an extension at the end of the name, the Finder should assign it the correct resource information. And I imagine a native version of ResEdit may come out sometime in the next year (before people stop using classic to run other apps).
 
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