Unable to open a dmg file

M

maverion

Registered
I created an image of an external hard drive to back it up, then I checked it and it opened fine. I moved the file to another drive and initialized the original drive and dropped the dmg file back onto the drive. Now it won't open. I really need the files on that drive. Is there any way at all to open it if even for a short time to retrieve the files?

Hoping to hear some advice.
 
Type of Macintosh, amount of RAM, version of OS X you're running, the specific drive format of the drives in question (HFS+? FAT32? GUID? APM?), type of drives (USB? FireWire? eSATA?), format of the DMG (read-only? read-write? compressed?), the exact wording of any error messages you receive, the step-by-step process you're trying to do, and any other information you may think is pertinent to helping you solve your problem.

You can't call a mechanic and say, "My car doesn't work -- what, exactly, is wrong with it, and how do I fix it?" You can't do the same with computers, either. We need very detailed information.
 
Also, if the "other disk" where you dropped the DMG was FAT32 formatted, the maximum filesize is 2GB, so if the DMG was bigger, end of it are lost.

(If you need to use FAT32 disk, try the split command on Terminal.App to split and cat to combine the splitted file back)
 
To create the image originally, I was using an older imac mini, which has been sold now, so I can't give specifics, but it was not an intel machine. It was purchased just before the intels came out. I was probably running Mac OSX 10.4.11 and it had 1 GB of RAM. I was also using Disk Utility 10.5.8.

I was having problems with a 500 GB Maxtor One Touch 4 PLUS external hard drive. I also remember compressing the image when I made it. I think I also made it Read-Only, but I cannot be sure. It had about 430 GB of files on it and it compressed to 398.3 GB. Temporarily I moved it to another Maxtor drive, but this one was 1.5 TB. All of these drives were Mac formatted. All my drives are also firewire. Currently the image lives on the original 500GB hard drive where the files were originally housed, so I can only retrieve so much because some of the info is now overwritten. I tried to reimage another drive with the image that won't open and that won't work either.

I was hoping maybe there was Software that could rescue the image, but that's probably too much to hope for...

The error message I get when I try to mount it is "no mountable file systems" but like I said, it did mount right after I created it.
 
So the disk image would mount correctly on the older Mac mini, yes? Did the disk image ever mount correctly on another machine before it started giving you the error?

Try mounting the disk image from the command line, using syntax from the Terminal like this:
Code: 
sudo hdiutil attach file name.dmg
...where "name.dmg" is the full path and filename of your DMG file. If you're not experienced with the command line, then an easier way might be to launch Terminal, type "sudo hdiutil attach file " (note the space at the end!), then drag-and-drop the DMG file from the Finder onto the Terminal window. The full path and filename should then automatically be filled in. Press enter, enter your administrator password when prompted (be aware that even though you type your password in the Terminal, nothing will show -- this is normal and is for security reasons -- rest assured it's accepting your keystrokes, though), and see if that will mount the DMG.

If it does, I would highly recommend getting the data out of that DMG and perhaps into another one.
 
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