“Identical” DMGs: one installs, one does not

dmg

We've got a DMG from a vendor that we put on our web server for download. After download, the file on my Mac (OSX 10.10.1) is identical to the original file (did a hex compare), and the DMG mounts fine… but the installer inside the DMG will not work after download.

To put it a different way, I have two seemingly identical DMG's, both of which mount, but only one of which will actually run the installer in the image, once mounted.

The permissions were slightly different between the two DMG's after download. Changed them so they are now identical.

We've tried this on three Macs with at least two versions of OSX, and the results are the same.

What else could be wrong? Is there anything in the OS security settings that could have saved some information about the file having come from the internet and blocking the installer somehow? If so, where?

Best Answer

There is information in extended attributes.

What is the setting in Preferences/Security & Privacy/General "Allow apps⋯"?

This needs to be set to an appropriate value to allow non-App Store apps to be opened.

Related Solutions

DMG mounts but does not auto-open

Here are a few online guides to creating auto-opening DMG files.

From the first guide by Bill Bateman, step 23 seems to be the key:

Click Convert on the toolbar. Enter a new filename and make sure the image format is compressed. Click Save. This creates a new image.

Another guide (via this post) has a bunch of information. The info regarding the auto-open piece is here:

But we found that the .dmg doesn't always open up its window when mounted. This “autoOpen” utility solves that problem: http://autoopen.nibfile.com/

One of these two guides should help you set up the auto-opening DMG.

Unique volname for DMGs

After a lot of searching and much cursing, I think that this is really a problem that practically nobody is aware of or concerned about. Still, I was able to find a solution, it's not great, but it should work. The idea is to mount the DMG in a known directory with some random name -- this name (the last element in the -mountpoint path) will be the name property of the disk. So using this I walk over all of the disks and look for ones with a matching name -- complain if I find none or more than one, otherwise, I have the needed object ready to work with.

mnt="some-random-name-$$"
hdiutil attach -readwrite -noverify -noautoopen \
               -mountpoint "/tmp/$mnt" "/tmp/out.dmg"
/usr/bin/osascript <<-EOF
      tell application "Finder"
        set myDisks to every disk of desktop
        set theDMGDisk to ""
        repeat with d in myDisks
          if name of d = "$mnt"
            if theDMGDisk = ""
              set theDMGDisk to d
            else
              error "Too many attached DMGs found!"
            end if
          end if
        end repeat
        if theDMGDisk = "" then error "Attached DMG not found!"
        -- found a single matching disk, continue
        tell theDMGDisk
... etc ...

Best Answer

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DMG mounts but does not auto-open

Unique volname for DMGs

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