I am trying to open a DMG file to install an OS X app. I get the error The following disk images couldn't be opened. Invalid Argument. I have tried to open other DMGs that I successfully managed to mount earlier and they are failing too. So the issue is not with the current DMG only. I restarted and that did not make a difference. I ran First Aid in DiskUtility and it reported that my drive was corrupt and needed repairing. I therefore restarted my mac with cmd + r pressed, selected Disk Utility and ran the repair. The repair failed after running for about 5 minutes. I would like to keep the contents of the drive if a solution exists that allows. What should I do now?


I did a time machine backup and let the iMac go get its drive formatted etc. I then attained a macbook air, and did a Restore From Time Machine onto it such that I have back where I left of on the iMac. I then tried to open a new DMG, and the same error came up. I ran First Aid on the mac air drive and it reported it to fine (Ran Successfully).

This is therefore not a drive issue right (first aid on the mac air succeeded)? What could it be, and how can I fix it.

  • 1
    Sounds like your question shouldn't be about DMGs but about how to save your data. Are you still ale to boot into OS X and use things like normal? If so, copy your important files onto an external drive. I don't know if doing a time machine backup at this point would be a good idea or not... But if you have a Time Machine backup on hand from before your problems started, restoring your Mac using a Time Machine backup may be where this goes.
    – kal-al
    Commented Jun 9, 2016 at 5:58
  • Will re-installing OS-X fix this issue, before I do so?
    – pnizzle
    Commented Jun 10, 2016 at 0:13
  • You mean as a fresh install? You may need to do that in conjunction with re-formatting the drive, and restoring from Time Machine or your backed-up files would be part of that. But this isn't something I've done at least not recently, so you may need someone else to come on here and give you better advice.
    – kal-al
    Commented Jun 10, 2016 at 0:16
  • Please confirm you have a complete Time Machine backup on external drive. If DiskUtility Repair (from System Recovery mode) has failed, then reinstalling OS X is your next step. You may not be able to reinstall without doing a full "erase and reinstall" - so you will rely on your Time Machine backup to restore your files later in the process. Others people may help you better if you confirm your system details - size of disk, type of disk (spinning HDD or solid state SSD or fusion drive), age and type of system. This sounds like corrupted system on disk - nothing to do with opening DMGs. Commented Jun 10, 2016 at 12:53
  • Yes, I have done a time machine backup. Have submitted the machine to the guys that handle such since thats their job :)
    – pnizzle
    Commented Jun 14, 2016 at 1:14

2 Answers 2


I had the same problem, and managed to open .dmg files by going into Disk Utility>File>Open Disk Image. Once opened in Disk Utility, Double Click (Right Click) the icon and click show in Finder. Then I could install what I wanted! Hop it works for you!

  • This worked for me. Commented Oct 20, 2017 at 8:20
  • Awesome. Saved my day, with Canon's broken-ass setup thing for their printer which refused to open via normal click-on-finder route.
    – StaxMan
    Commented Feb 1, 2019 at 4:48

If the Time Machine backup you used to restore the Mac was created after you started noticing problems, maybe whatever drive corruption there was messed up some files that were backed up, leaving you with a good drive but still bad system files. If you have an older Time Machine backup from when the Mac was functioning properly, that might be better to use.

Seeing as you can still basically use the Mac, I would recommend reinstalling the iMac from a fresh install, and then manually moving over your apps and files or using Migration Assistant to transfer files and settings from the MacBook Air to the iMac.

  • Can migration assistant take stuff from a time machine backup? Never used it before
    – pnizzle
    Commented Jun 15, 2016 at 2:25
  • @pnizzle I believe so. So you should be able to either use the Time Machine backup or the MacBook Air with the state of your files as you want, and from a clean install on the iMac, you can restore files and settings.
    – kal-al
    Commented Jun 15, 2016 at 2:33
  • I can not afford to do a clean install right now. Have wasted enough time for one day lol. Would you know of any other way to mount DMGs other than the default and terminal?
    – pnizzle
    Commented Jun 15, 2016 at 2:56
  • @pnizzle I personally don't know, but if you really need to open it, try to find someone else with another Mac. When you have a chance to reinstall El Capitan such that it's like new and DMGs open, you will be able to use Migration Assistant to restore your files and settings.
    – kal-al
    Commented Jun 15, 2016 at 3:53
  • @ka'al i did that. I restored from a Time Machine to a new mac and then faced the same problem. I am going to have to select specific file using migration assistant if possible. Thanks for now.
    – pnizzle
    Commented Jun 15, 2016 at 4:22

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