Hi, I am a bit confused about your suggestion to trash the mounted .dmg file after installing an app. I normally unmount the image and trash the .dmg. Is it a wrong procedure? Does it leave unwanted remnants? Thanks, and keep up the great work

I read about this whole topic already on Mac Kindergarten earlier this week.

@emanuele, yes, you are correct, and I will clarify the post. When I state to put the image in the trash, it means to unmount it. I have found many users have a hard time understanding what an “image” is. I should clarify.

Ha, I was collecting those dmg’s in a file till I figured out/read somewhere that they get tossed after gettin’ the application.

Thanks for the article!

I find with all new Mac users, they tend to mount the DMGs and run applications directly from them (unless there are visible instructions to do otherwise, which some developers are kind enough to include).

On top of that, they never trash any of the DMG or ZIP files.

I have high hopes that Apple will sometime address this major confusion point for new users.

@JimB, exactly, people get so caught up in the idea that deleting is destructive, that they tend to hold onto everything. As time goes on, you forget what you really need or not, and end up just keeping everything. Glad this helped to explain a few things to you.

I have a file that I save all my DMGs in. I find it is helpful when setting up a new machine to have a copy of all the bits of software I have downloaded over the years.

Hi, Scott,
Can you explain why it is necessary on a Mac to drag discs and other items to the trash (eject) before removing or disconnecting them? I don’t ever remember getting into trouble for doing so on a PC, but my Mac scolds me any time I forget to do so.

@Matt Nikos:

When you eject a disk image or physical device such as a thumb drive or external hard drive, you are ensuring that any remaining changes made to the files and other information on that device gets updated before you pull it out of the port. Mac OS X is based on BSD, which, like other Unix derivatives, will cache any changes in RAM before committing them to the physical device. This speeds up transfers for the end user, but the downside is that the changes aren’t final until the drive is ejected. This means that if you don’t eject before removing the hardware, there’s a small chance you may “lose sync” with the data still in RAM and could end up with corrupted files. By ejecting every time, you are ensuring that your data is not corrupted.

I may be wrong, but I believe that the reason you probably never had an issue with it on a PC is because you can tell the OS not to warn you about such things. Also, Windows does handle such caching a bit differently; given sufficient time the data in RAM will sync with the device in a background process, making an eject command unnecessary most of the time.

P.S.: Scott, sorry if I stepped on your toes here but I figured I’d throw in the answer since I was here. No offense intended.

@WetcoastBob, yes, drive space is cheap these days and you can in fact safely safe anything you like. I would be a little worried that the files are out of date. Software is updated so often these days, most installers do not stand the test of time.

Then again, I do find myself downloading things many times over, and your method could save some people some time, just make sure you are still using the most current version.

@Morgan, no toe stepping at all, actually, thank you for taking the time to write a reply. This has always been our hope, to get some of the more advanced users in here, helping others out.

I wan’t to emphasize the “small chance” of “loosing sync” you pointed out. For file copies off of a mounted drive, in the case of Mac OS X, if the file copy dialogue is no longer on your screen, the files in fact were moved.

I am not 100% sure, but on a copy onto, the same should apply.

This is in direct contrast to Windows, where a file copy can continue, even after the file copy dialogue is gone, and long gone, as in seconds after, the files are still catching up. This has been the case since XP, and up to Vista, though both are marginally different at how they approach it.

The main reason the OS is “scolding”, at least in my guess, is the overhead to watch the removable media, and see if it is in fact in use during a file operation is high. Easier to just alert the user to a best practice case, and not have to run a background process that will watch all removable media.

in closing, remember as Morgan states, it is a “small chance”, OS X is robust enough to know that at any time, a power failure, battery failure, or stray cat can cause your computer to shut down.

Firewire is the only one I am really careful with, as you can in fact fry the firewire bus under certain also rare cases by skipping the unmount.

One of your best and most helpful articles to-date, THANK YOU!
Did you explain about the additional downloads folder (new in Leopard) in the dock that is in addition to the downloads folder in the users area?
Another reason to delete duplicated files is to keep maximum hard-drive spare for what counts. I always run out of hard-drive space.

@Bill, the Dock is something we are working on, Caroline has been writing about it now for a month, so I assume it is going to be great, or, maybe, she is just lazy

Any item in the Dock is not a real file, but an “alias” of sorts. So while Leopard comes with a folder that is “Downloads” it is nothing more than a “shortcut” or “Alias” to the real downloads folder in your home folder.

Same for anything in the dock, which is why you can remove anything from the Dock and it is not destructive.

Hope that helps.

I loved this post because I’m a minimalist and have but worried. What do you mean by one’s downloads? The dialog box that shows what you’ve downloaded that invites you to clear it each time? Thanks!

@Mary, by downloads, we mean the actual files that are downloaded. In Leopard 10.5, they will end up in your Downloads folder, which is in your home folder. You can access this by going to the “Go” menu in the Finder, and selecting “Home” then opening the “Downloads” folder.

The dialog box you are talking about is just a download history in Safari, that shows you what you have downloaded in the past. You can click on the small magnifying glass icon and it will also take you right to the file you downloaded, assuming it still exists and you have not deleted it.

I am an experienced win and linux user. This post helped me to understand dmg-files, which seemed to behave strangely. Thank you…

I’ve posted a videocast demonstrating the download process at Learning OS X. You can see the video here.

http://www.learningosx.com/2008/06/where-do-my-downloads-go/

Scott:
The best thing about your site is that you explain in language that anyone (even I) can understand. Too often, those who know don’t know how to communicate to those who don’t know (I’ve found this problem asking questions in Apple Support Discussions), which leaves the questioner (me) feeling dumb and, at times, more confused than before. Thanks for the clarity!

@Jerry, thanks for noticing. We actually talked about that very aspect. As you probably know there are 100’s of Mac sites out there, our edge over them, if you can call it that is we try to being it down to normal language levels. People do not care about what SATA, eSATA, USB, and all the other acronyms are, we just want to teach you what the general concepts are. Once you get the general ideas, there are plenty of places to dig deeper if you so desire.

Thanks again.

I just got my first mac (iMac OS X) and was gong to download the unarchiver, when the download window popped up it and states “open with stuffit (default)” or save file. Does this mean I already have Stuffit?

@John, yes, this means that at some point, you installed Stuffit Expander. You could delete it, safely, I have not had it installed in years, and find Unarchiver to work better, and be easier to locate and get ahold of versus the way in which Stuffit is hidden for the free version on their website.

Hi. I’m a fairly new Mac user. I switched from windows early this month. I’m totally blind so I use Voiceover and what a brilliant thing it is. Thanks for this website. i’m learning a lot from it. Your bookmark organisation strategy is excellent – I should have done something like that a long time ago on windows. And thanks for mentioning unarchiver. I downloaded stuffit because I didn’t know there was another alternative. It’s now going to be removed.

@Dannie Thank you for the comment. I have always wondered how well a blind person can get along on the Macintosh. I am aware of the Accessibility options that Apple provides, and I am aware, that in my light browsing of them, comparing the features to the offerings on Windows, I find Apple’s superior.

Far from perfect, as myself, with fair enough eyesight, find some things frustrating, and I have a luxury others may not.

If there is anything in particular you get stuck on, try to find a relevant post, and leave us a comment. Please mention your disability so I can compose my reply appropriately.

Good luck with your new Mac.

Thank you so much.

I’m new to Mac and this has been very helpful.

They seem to forget to explain how to do the simple things.

Excellent article. I am a two week mac newbie & I love my iMac. I have been stuck on dos pcs since computers had two floppies and no hard drive. Vista was my last straw. I have only had two questions/problems and have been searching the net for answers. This is one topic. What to do with the dmg file after the app has been installed. From a windows perspective, you don’t get rid of anything program related. So even tho I have read to eject the dmg, I just wasn’t convinced. I do have one question tho, after installing the app, can the dmg be saved to an external drive and be reused or is it “empty”? I don’t want to have to search the net again for say tux paint & other cool apps if I accidently trash the app. I am so windows oriented, the process on the mac to uninstall apps is awesome as well as graphics, processing speed, quietness, safety, and …………

@gonzobe,

This is one topic. What to do with the dmg file after the app has been installed. From a windows perspective, you don’t get rid of anything program related. So even tho I have read to eject the dmg, I just wasn’t convinced.

A dmg is literally a single file, that when opened, will mount a virtual disk. You can eject (put in trash) the virtual disc that the dmg mounts, with no harm. Once you have copied the files you need from the dmg, or ran the installer, you can safely eject the white icon, and also throw away the dmg with zero ill effects.

<blockquote I do have one question tho, after installing the app, can the dmg be saved to an external drive and be reused or is it “empty”? I don’t want to have to search the net again for say tux paint & other cool apps if I accidently trash the app.

Yes, you can save the dmg to an external drive, or you could just keep in on your computer in some folder where you decide to save such things. It is not really a habit I would recommend getting into. You are saving a file that is an installer, or an application for a specific version of software. Most Mac software developers are releasing software updates on a speedy and regular basis.

You will end up saving a dmg that has an older version of software on it. If for whatever reason you ever need to reinstall it, I would just go to the website, and download it again. This assures you that you have the most current version. Most apps are relatively small, and can be downloaded in a few minutes.

Something like Adobe’s Creative Suite may be worth saving the installer, but even that is not that terrible of a download if you have a decent internet connection.

can the dmg be saved to an external drive and be reused or is it “empty”?

The dmg is not empty in any way. As a matter of fact, a dmg for a software installer is in almost all cases going to be a read only dmg, meaning, you can not alter it even if you were desirous to do so. You may be able to move an icon around within the window, but you would not be able to delete the files on it. Feel free to try, no harm can come from it, and it will help you understand the process a little better.

If you are worried about being able to locate the files, rather than saving the dmg, perhaps you should consider developing a system of bookmarks where you bookmark the download page for the software. My personal recommendation is that saving a dmg is a waste of disk space, and will only get you in potential trouble, as you will be installing old software.

Consider the following scenario:
Download and install coolapp version 1.3
Save coolapp 1.3 installer on your computer for future use

coolapp 1.3 has an internal update mechanism. You launch coolapp 1.3 and it says “hey, we have released coolapp 1.4, would you like to update?

Of course, you do update, and are now at coolapp 1.4. This goes on for a few months and you end up at coolapp 1.7, and all of a sudden, something goes wrong with coolapp 1.7.

You revert back to your saved dmg, and install coolapp 1.3. However, all the files and preferences for coolapp are in the format that coolapp 1.7 used to read. You are now asking coolapp 1.3 to understand an aspect of itself that was not yet programmed into it at the time of release.

In extreme cases, the above procedure can corrupt your files to the point that they are broken. Good developers will protect you from this. For example, if you try to open a newer iPhoto library with an older version of iPhoto, it simply will not allow it to happen, and tell you to update iPhoto first.

I do strongly suggest you look to sites like macupdate.com for your software as well, not so much to locate and download the software, it is always better to go directly to the source of the software, but more to read the reviews.

There is a lot of software out there, much of which is junk, or could potentially cause your computer to become unstable. The reviews on MacUpate can be helpful. Another tactic is just a google search for “Mac OS X _insert software name here_ sucks”. That will get you a good idea of others impressions of the software as well.

Let us know if you have any other questions.