# How do I open a DMG file?



## wainwra (Sep 29, 2005)

It's so horribly embarrassing to have to ask this.  I'm a very experienced Windows user, and I'd have thought I could manage this.  I can't.

I have a Mac (a PowerBook G3) which I got second hand, in order to find out a bit about the Apple world (and to give my wife a machine she can use for her emailing).  I'm really struggling to work it.  I could really use some help.

Right now, I have been trying to install Folding@Home, which is delivered via a DMG file.  I KNOW that I've opened these before, because I can see some on the desktop - eg Firefox, which is installed and working.  But now, when I click on (any) DMG file, all that happens is that "Disk Utility" opens.  That told me to select a disk or folder.  I clicked on a disk.  (Now what?)

I've done a lot of searching, and I've found a reference to "repairing associations".  How would I do this?  I've looked at the menu options in Disk Utility and see nothing useful.

Please help me.  I would really like to be a Mac bigot - I'm sure it's my calling.  But I'm really struggling to work out how to use a Mac.  

(And does anyone know of a good website for experienced Windows users who are new to Macs?)


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## Lt Major Burns (Sep 29, 2005)

dmg stands for Disk Image. when you open them, it mounts what appears to be a disk drive on the desktop, alongside cds, dvds and hard drives.  you then open up this disk image and take out /copy what ever was in it to your hard disk. once you have finished with them, "eject" the disk by trashing it.  you shouldn't have a disk image on your desktop for any longer than it needs to be. it's just messy.

this .dmg, it seems, has a wrong file association with it, it's trying to open disk utility, instead of Disk Image Mounter.  right click/ctrl-click on it and select open with... (while holding alt) Disk Image Mounter.

this should work.  use the contents/copy the application across to your applications folder, and then eject it.


what system are you running? for example i am running MacOS X 10.4.2.  you can find out in the apple menu>about this mac.


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## barhar (Sep 29, 2005)

'.dmg' files can be opened with a few utility applications - 'Disk Utility', 'DiskImageMounter', and 'StuffIt Expander'.

01. To answer your question of 'when I click on (any) DMG file, all that happens is that "Disk Utility" opens. That told me to select a disk or folder. I clicked on a disk. (Now what?)' - once 'Disk Utility' opens ...
01.01. Locate and click once on the '.dmg' file (you initially double clicked on) in the lower portion of the left side list. 
01.02. Next, click on the 'Open' button - in the toolbar (along the top of 'Disk Utility's window). A (ghost) disk image will now appear on your 'Desktop'.

After installing the software from the disk image, click on the disk image and eject it ('Finder' 'File, Eject ...', 'Command E', or via a contextual menu ['<control>' click or right button click - 'Eject ...'])

02. By default the application to open '.dmg' files should be 'DiskImageMounter' [not 'Disk Image Mounter']. To return 'DiskImageMounter' as the default application, to automatically process a '.dmg' file:
02.01. Click once on any 'dmg' file. Select 'Finder's 'File, Get Info' menu item. A 'Get Info' window will appear.
02.02. From the 'Open with:' popup menu (you may have to click on the disclosure triangle to see it) select 'DiskImageMounter'. [Or, you may have to click the popup menu's 'Other...' menu item and navigate to the '/System/Library/CoreServices/' folder to select 'DiskImageMounter'.]
02.03. Click on the 'Change All...' button. An alert box will appear.
02.04. Click on the 'Continue' button.
02.05. Close the 'Get Info' window.
02.06. Double click on any '.dmg' file to test whether MacOS X actually accepted the changes you just made.

Note. Even if you applied the changes of '02.' above - do not be surprised, if at a later time, the settings change ... by themselves (actually, by MacOS X) ... ... ... just think of it a another MacOS X 'feature'.

03. Also, dragging a '.dmg' file onto 'StuffIt Expander', will result in its (ghost) disk image appearing on the 'Desktop'.


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## wainwra (Sep 29, 2005)

Lt Major Burns, thank you very much for your quick reply.  I tried to open the dmg file with DiskImageMounter, but I wasn't able to find that on my system.  Where should I have looked?  I looked in Applications, and in Utilities, and in Library, but the closest I could find were Disk Utility and Disk Copy.

I tried opening the file with StuffIt Expander, (which was there), but that didn't do me any good - I could see StuffIt Expander loading (the stuffit vice-like icon appeared in the err, system bar is it called?  and started bouncing), but after a while, Disk Utility also loaded, and StuffitExpander went away, without any new window appearing.  Then the Disk Utility window opened again.

I found Repair File Permissions, by the way (under First Aid in the Disk Utility, if there are any other newbies reading this), and ran that.  Took a while, and found and fixed lots of things, but didn't help me with my problem.

I'm running Mac OS X 10.2.8


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## wainwra (Sep 29, 2005)

barhar, thank you too for replying.  

I'm having problems with your very first instruction "01.01. Locate and click once on the '.dmg' file (you initially double clicked on) in the lower portion of the left side list."  (this is from Disk Utility).  I don't see a lower portion on the left side list.  I have two portions.  The left hand side has a (drive icon?) with the text "3.82 GB IBM-" and then under it, indented, the same icon again, with the text "\".  

I tried double clicking on that, but nothing happened.  Having selected that "\", the right hand portion of the window fills with information about the hard drive, saying not very much, including "mount point: /" "format: UFS", some size information and "Number of Folders: Unknown"


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## wainwra (Sep 29, 2005)

barhar, I forgot to reply to the second part of your reply, where you say that DiskImageMounter should be in System\Library\CoreServices.  I couldn't see DiskImageMounter there.  Alphabetically it went from coreservicesd to Dock.

Does this mean that the application has somehow got deleted from my machine?  That seems extremely unlikely given the very infrequent use this machine has had, both by me (who never delete anything) and by my wife (who has never done anything outside of mail or browsing).


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## RacerX (Sep 29, 2005)

wainwra said:
			
		

> Does this mean that the application has somehow got deleted from my machine?


It means that they aren't using 10.2 and they aren't quite sure what to advise (in later versions of Mac OS X Disk Utility and Disk Copy are merged into one app). So barhar's instructions were wrong for your system starting with... 01.

If anything other than Disk Copy is opening when you double click on a DMG file on your system... then the file is corrupt or incomplete.

What it sounds like to me is that the download of Folding@Home wasn't completed. I would suggest trying to download it again (using Safari).

I just tried downloading the GUI and Screensaver versions on my system (which *is* running 10.2) and didn't seem to have any issues. When the download was complete Disk Copy mounted the image.



> (And does anyone know of a good website for experienced Windows users who are new to Macs?)


Honestly, experienced Windows users are going to have a harder time than the average user when moving to Macs because they are used to being an _experienced_ user.

For your situation, you are going to need to find a used bookstore. You need 10.2 information, which is rare these days both on the net and in most  bookstores. I know that both CompUSA and MicroCenter have older books on sale so there is a good chance you'll find some 10.2 references there.

There is also the option of finding a Mac consultant/specialist (which is what I do for a living) who can take the time to show you how some things work. Additionally you could check into Mac User Groups. I co-run a General Mac SIG and help out with a Mac OS X SIG in my area, and we answer many questions about things just like this.



*For anyone reading this...* 
Help comes best when you let people know what operating system you are using when you ask a question.

People trying to help should (if it hasn't been noted in the original post) ask what operating system the person is using. And if it is an operating system that you are unfamiliar with you may want to skip trying to answer.


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## wainwra (Sep 29, 2005)

Thank you RacerX - very clear answer!  

However (sigh)...

1.  I tried re-downloading the file - no difference.   I also was able to click on some dmg files which I still have on my desktop, and they also don't open any more.  They used to - I know this, coz I've previously installed VNC and StuffIt Expander, and those work fine, but their dmg files do just the same as Folding@Home's does (which is, to start Disk Utility).

2.  Apologies re not giving the OS version.  I thought the OS was Mac OS X, and that version number differences were like Service Pack levels in Windows - not something which affects how the OS works.  Now I know better, I guess.  

3.  Mind you, I'm pretty certain I bought this code in early January 2004, and that I bought the latest version available at the time.  I've been applying software updates whenever they came out, and thought that that would keep me current.  I suppose then, that going to 10.3 or 10.4 would be something I have to pay for?  Is it expensive?  If it's just a small fraction of the cost of the 10.2 in the first place, then I'll just upgrade.

So - my main question is now this:  DMG files no longer seem to open on my machine.  What can I do to restore normal operation?


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## RacerX (Sep 29, 2005)

Well, first, if DMG files are starting up Disk Utility, then somewhere along the line the system was told that that was the helper application for opening them.

To fix this, single click on one of the DMG files. Then go to the _File_ menu down to _Get Info_. You should be presented with a panel with information about the selected file (in this case, one of the DMG files).

Usually the General information arrow is pointing down (showing general information), below that there should be an arrow next to _Open with_. Click that arrow. Right now I'm guessing that it lists Disk Utility as the default... we need to change this to Disk Copy. After you have Disk Copy selected, click the _Change All..._ button.

Odds are that some other app (I'm guessing Firefox, but it could have been StuffIt) changed this setting because the developers forgot that in 10.2 disk images are opened with Disk Copy (and not Disk Utility).

As for versions of Mac OS X... 10.2, 10.3 and 10.4 are whole versions (like Windows 95, 98 and ME, or Windows NT 3.51, NT 4.0, 2000 and XP). The updates (like 10.2.8) are like the Service Packs in the Windows XP line.

As such, each version is independent of the previous one... and they each cost $129.00 when new (currently, that would be for 10.4). Older versions are often sold at a reduced rate by third party venders (Apple rarely continues to sell older versions).

As for going up to 10.3 or 10.4... there are factors to keep in mind. First, can your PowerBook run 10.3 or 10.4? 

You said you have a PowerBook G3. 

Does it have USB ports (built into the system, not via a PCMCIA card)? If yes, then you can move up to 10.3 if you would like. 

Does it have Firewire ports (built into the system, not via a PCMCIA card)? If yes, then you can move up to 10.4 if you like.

If your system has neither, then you have a PowerBook like mine... and 10.2.8 is as high as Apple supports on that system.

Of course then comes the question of if you should move up. This depends on how fast your processor is (266 MHz, 300 MHz, 333 MHz, 400 MHz or 500 Mhz are some of the speeds that the PowerBook G3 was released at), how much RAM you have (256 MB is the minimum I would run 10.2 at, 512 MB would be better and needed for 10.3 or 10.4) and how large your hard drive is (early PowerBook G3s required partitioning the drive with an 8 GB beginning partition for Mac OS X, later PowerBooks didn't need this).

So knowing more about your system would help to determine what version of Mac OS X would be right for you... if you felt the need to upgrade at all (which you don't have to).

Hope this helps a little.


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## barhar (Sep 29, 2005)

It is the responsibility of the poster to post explictly the model number, System / MacOS X, application name, etc. No one should have to request the obvious, no one. 

By posting 'Disk Utility' (in the original post, even though no specific MacOS X version was mentioned) - yes, I can see why 'Lt Major Burns' and I replied as we did.

While I have the ability to quickly reboot in various MacOS X 10.2, 10.3, and 10.4 versions (and, 10.1 if needed) - I do not do such for each MacOSX.com post I reply to.

'Apologies re not giving the OS version. I thought the OS was Mac OS X, and that version number differences were like Service Pack levels in Windows' - well, you thought wrong.
Sadly, MacOS X remains a beta OS. With every '10.x.0' release Apple shuffles many controls of the various 'System Preferences' utilities (which renders many related AppleScript scripts / applets useless); plus, restricts the Mac User Interface and experience more and more as it conforms to a more Windoze like format and experience (yes, even though it is UNIX based).

Again, before anyone posts a question or problem - they should review the existing forums posts and replies; and, if then creating a post - being very specific of the problems and related hardware, software, etc.


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## wainwra (Sep 29, 2005)

RacerX - THAT WORKED!  Thanks so much!

I think the last thing installed was StuffItExpander (which was delivered via a DMG file) - so it's the most likely candidate for all this, btw.

Re potential upgrades, my PowerBook G3 is pre USB and pre firewire.  It has a 4Gb hard drive, runs at 250MHz and has 160Mb RAM....

...  which rather answers the question quite nicely I think!


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## wainwra (Sep 29, 2005)

barhar, as I thought I had explained, I am a very novice Mac user.  As I've explained already, I thought that Mac OS X WAS the version number (X=10, right?) and that the point numbers after it were minor (I'm typing this on a Win XP machine - I would never dream of saying it's Windows 5.1.2600, which is actually what it is.  Nor would anyone ever ask me.)

Well as you rather bluntly put it, I was wrong.  I apologise.  I'm afraid I'm a novice Mac user.  

But isn't it novice users who most need help?

Speaking now as someone with considerable experience of IT support, I think RacerX's advice about how to handle questions like mine makes a lot of sense.  Clearly we should be encouraged to provide all the pertinent information upfront.  However, it's worth bearing in mind that precisely because we're novice users, we might not know what that information actually is.

But thank you barhar, for the information about how Apple handles version releases.  Sounds frustrating.


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## RacerX (Sep 29, 2005)

barhar said:
			
		

> It is the responsibility of the poster to post explictly the model number, System / MacOS X, application name, etc...
> 
> While I have the ability to quickly reboot in various MacOS X 10.2, 10.3, and 10.4 versions (and, 10.1 if needed) - I do not do such for each MacOSX.com post I reply to.


Maybe you could add that warning to your signature. 



> well, you thought wrong.


If you don't have the temperament to help, then maybe you should avoid doing it in the future. As someone with experience in these areas you should have asked questions that someone new to Macs wouldn't have known to ask.

But as you are new to the forum, maybe you aren't used to this type of post.

My advice... get used to it. I've been answering questions on this site for four and a half years now, this is nothing new (including your response).

His mistake is understandable. Yours was less understandable, but still understandable. At least Burns asked the question (he has been around a little longer  ).



> Sadly, MacOS X remains a beta OS.


Opinions vary.  




			
				wainwra said:
			
		

> I think the last thing installed was StuffItExpander (which was delivered via a DMG file) - so it's the most likely candidate for all this, btw.


Thanks for posting that follow up. It is good to know that the new version of StuffIt Expander causes these types of issues... Sorry that you had to be the one to find this out for us.

Hope you take the time to explore Mac OS X a little more. If you need references on Mac OS X v10.2, just PM me. I work with pretty much all versions and can point you to some of the better resources. Plus I have a number of clients running Mac OS X on the same type of PowerBook you have, so I have a pretty good idea of the issues that may arise.



Oh, by the way... welcome to the forum!


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## barhar (Sep 29, 2005)

'... information about how Apple handles version releases. Sounds frustrating', while is may sound frustrating, or be confusing - it really should not be.

Think of MacOS X this way ... MacOS X version 10.x.y.
Every time Apple increments 'x' (called a 'major' release) you pay around $129 (every 12 to 18 months).
Every time Apple increments 'y' (called a 'minor' release, or an 'update') you can download the update - automatically via 'System Preferences' 'Software Update', or from Apple Downloads - for free.

[
Added 30 Sept. 2005 - 00.32
As noted by fryke (below) - the PowerBook G3 wamwra has can only go as high as MacOS X 10.2.8.

Thus the following ...

'You currently have MacOS X 10.2.8, so - to install MacOS X 10.3 ('Panther') you would have to purchase it. To update to 10.3.1, 10.3.2, to 10.3.9 you can obtain the respective Update installer from Apple Downloads. The same applies for 'Tiger' 10.4 - 10.4.2 (with 10.4.3 expected soon).'

... does not apply here specifically.
]

The benefit of installing 'Panther', and perhaps 'Tiger' - improvements in the OS overall, new features, etc.

One benefit of MacOS X 10.2.8, is the ability to easily connect to System 8.x and later Macs Systems / MacOS X'es. MacOS X 10.3 and 10.4 removed this user friendly 'ease of connect' feature.
'Panther' - MacOS X 10.3.4 is quite stable and zippy; yet, to run 'iLife '05' - 10.3.6 or later is suggested.
MacOS X 10.4 handles virtual memory ('swapfiles') most effectively.


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## fryke (Sep 29, 2005)

However: I don't think the 250 MHz Wallstreet supports anything higher than 10.2.8. So you're fine.


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