Skip navigation

Won't mount DMG files unless in safe mode

2598 Views 9 Replies Latest reply: May 7, 2012 9:08 PM by Topher Kessler RSS
peakoverload Level 1 Level 1 (0 points)
Currently Being Moderated
May 7, 2012 2:27 AM

This has suddenly started happening on my new iMac running Lion and I don't know why or how to fix it. It was fine for months and then the other day this started happening.


If I try to mount almost any DMG file I just get an error message saying that there is no mountable file system. I know that these are not corrupt dmg files because these are ones that I have mounted before, it affects almost every single one and more importantly if I reboot in Safe Mode every single one mounts perfectly.


Clearly then something is running in normal mode that is preventing dmg's from mounting but I don't know how to find out what. I went to System Properties>User & Groups>Login Items and removed everything that was there but that was just iTunes Helper and something called WDC something or other which was unchecked anyway and is just a utility that controls my external hard drives. With everything removed and rebooted still DMG files won't mount.


Safe Mode = DMG's mount

Normal Mode = DMG's won't mount.


Anyone know how I can find out what is causing this problem and/or how to fix it as it's annoying as **** and preventing me from easily updating software.

iMac, Mac OS X (10.7.3), 3.1Ghz Quad-Core Intel core i5
  • Radiation Mac Level 5 Level 5 (4,630 points)
    Currently Being Moderated
    May 7, 2012 3:50 AM (in response to peakoverload)

    Since you are using Lion I would recommend you restart the computer while holding down Command - R to boot into the Lion Recovery Partition. Then Go into Disk Utility there and run "Repair Disk".  Then run "Repair Permissions" twice. Hopefully this will resolve your problem.


    Hope this helps

  • Linc Davis Level 10 Level 10 (107,955 points)
    Currently Being Moderated
    May 7, 2012 6:15 AM (in response to peakoverload)

    Select one of the files and open the Info window. What application does it open in?

  • Topher Kessler Level 6 Level 6 (9,305 points)
    Currently Being Moderated
    May 7, 2012 6:55 AM (in response to peakoverload)

    Try rebooting the system into Safe Mode (hold the Shift key at startup) to see if the DMG will open either when in Safe Mode, or afterwards once you have again restarted the system to boot normally.

  • etresoft Level 7 Level 7 (23,905 points)
    Currently Being Moderated
    May 7, 2012 7:58 AM (in response to peakoverload)

    peakoverload wrote:


    This has suddenly started happening on my new iMac running Lion and I don't know why or how to fix it. It was fine for months and then the other day this started happening.

    Did anything else happen at around the same time? Such as installing anti-virus software?

  • Linc Davis Level 10 Level 10 (107,955 points)
    Currently Being Moderated
    May 7, 2012 10:38 AM (in response to peakoverload)

    Please read this whole message before doing anything.


    This procedure is a diagnostic test. It won’t solve your problem. Don’t be disappointed when you find that nothing has changed after you complete it.


    Third-party system modifications are a common cause of usability problems. By a “system modification,” I mean software that affects the operation of other software — potentially for the worse. The following procedure will help identify which such modifications you've installed. Don’t be alarmed by the complexity of these instructions — they’re easy to carry out and won’t change anything on your Mac.


    These steps are to be taken while booted in “normal” mode, not in safe mode. If you’re now running in safe mode, reboot as usual before continuing.


    Below are instructions to enter some UNIX shell commands. The commands are harmless, but they must be entered exactly as given in order to work. If you have doubts about the safety of the procedure suggested here, search this site for other discussions in which it’s been followed without any report of ill effects.


    Some of the commands will line-wrap or scroll in your browser, but each one is really just a single line, all of which must be selected. You can accomplish this easily by triple-clicking anywhere in the line. The whole line will highlight, and you can then either copy or drag it. The headings “Step 1” and so on are not part of the commands.


    Note: If you have more than one user account, Step 2 must be taken as an administrator. Ordinarily that would be the user created automatically when you booted the system for the first time. The other steps should be taken as the user who has the problem, if different. Most personal Macs have only one user, and in that case this paragraph doesn’t apply.


    Launch the Terminal application in any of the following ways:


    ☞ Enter the first few letters of its name into a Spotlight search. Select it in the results (it should be at the top.)


    ☞ In the Finder, select Go ▹ Utilities from the menu bar, or press the key combination shift-command-U. The application is in the folder that opens.


    ☞ If you’re running Mac OS X 10.7 or later, open LaunchPad. Click Utilities, then Terminal in the page that opens.


    When you launch Terminal, a text window will open with a line already in it, ending either in a dollar sign (“$”) or a percent sign (“%”). If you get the percent sign, enter “sh” (without the quotes) and press return. You should then get a new line ending in a dollar sign.


    Step 1


    Copy or drag — do not type — the line below into the Terminal window, then press return:


    kextstat -kl | awk '!/com\.apple/{printf "%s %s\n", $6, $7}'


    Post the lines of output (if any) that appear below what you just entered (the text, please, not a screenshot.)


    Step 2


    Repeat with this line:


    sudo launchctl list | sed 1d | awk '!/0x|com\.(apple|openssh|vix)|edu\.mit|org\.(amavis|apache|cups|isc|ntp|postfix|x)/{print $3}'


    This time, you'll be prompted for your login password, which won't be displayed when you type it. You may get a one-time warning not to screw up. You don't need to post the warning.


    Note: If you don’t have a login password, you’ll need to set one before taking this step. If that’s not possible, skip to the next step.


    Step 3


    launchctl list | sed 1d | awk '!/0x|com\.apple|edu\.mit|org\.(x|openbsd)/{print $3}'


    Step 4


    ls -1A /e*/mach* {,/}L*/{Ad,Compon,Ex,Fram,In,Keyb,La,Mail/Bu,P*P,Priv,Qu,Scripti,Servi,Spo,Sta}* L*/Fonts 2> /dev/null


    Important: If you synchronize with a MobileMe account, your email address may appear in the output of the above command. If so, anonymize it before posting.


    Step 5


    osascript -e 'tell application "System Events" to get name of every login item' 2> /dev/null


    Remember, steps 1-5 are all drag-and-drop or copy-and-paste, whichever you prefer — no typing, except your password. Also remember to post the output.


    You can then quit Terminal.

  • Linc Davis Level 10 Level 10 (107,955 points)
    Currently Being Moderated
    May 7, 2012 11:24 AM (in response to peakoverload)

    Please read this whole message carefully, especially the warnings, before doing anything.


    The changes to your configuration suggested here should be considered provisional; they may not solve your problem, or they may remove functionality that you find useful. If a third-party system modification that you want to keep is causing the problem, seek help from its developer.


    WARNING: Back up all data now if you haven’t already done so. Before proceeding, you must be sure you can restore your system to its present state, even if it becomes unbootable. If you’re not sure you can do that, STOP — DON’T CHANGE ANYTHING. If you’re dissatisfied with the results of the procedure suggested below, restore from your backup. I will not be responsible for the consequences, and I will not help, if you ignore this warning.


    You should either remove or update the following system modification(s), if an update is available from the developer:




    and definitely remove at least the following:


    WD SmartWare

    Terminus driver


    PACE iLok driver (required for Digidesign product; uninstall or deactivate temporarily)

    Nalpeiron (possibly required for other "pro" application)


    Whatever you remove must be removed completely, and (unless otherwise specified in this message) the only way to do that is to use the uninstallation tool, if any, provided by the third-party developer, or to follow his instructions. In some cases it may be necessary to re-download or even reinstall the software in order to get rid of it. I can't be more specific, because I don't install such things myself. Please do your own research.


    Here are some general guidelines to get you started. Suppose you want to remove something called “BrickYourMac.” First check the developer's website, say, for instructions. If you don’t find any, email the developer. Failing that, download BrickYourMac.dmg and open it. There may be an application in there such as “Uninstall BrickYourMac.” If not, open “BrickYourMac.pkg” and look for an Uninstall button.


    If you can’t remove the software in any other way, you’ll have to erase your boot volume and perform a clean reinstallation of the Mac OS. Never install any third-party software unless you're sure you know how to uninstall it; otherwise you may create problems that are very hard to solve.


    WARNING: Trying to remove complex system modifications by hunting for files by name often will not work and may make the problem worse.


    I recommend that you never reinstall the modifications marked with a dagger (†) above, if any. If your problem is resolved after uninstalling all the above modifications and rebooting, but you still want to use some of those not marked with a dagger, you can experiment with putting them back, one at a time, testing carefully after each step. Keep in mind that system modifications may be incompatible with each other or with future Mac OS updates, so it may not be clear which one is at fault.


    If you still have problems after making the suggested changes and rebooting, post again. Remember: if you don’t like the results of this procedure, you can undo it by restoring from the last backup you made before you started.

  • Topher Kessler Level 6 Level 6 (9,305 points)
    Currently Being Moderated
    May 7, 2012 9:08 PM (in response to peakoverload)

    I'd recommend the following. First download Pacifist ( and then open the application (you will have to wait 15 seconds, and then do not install any quicklook plugins when prompted). In this program, go to the "Pacifixt" menu and then choose "Display Kernel Extensions Report."


    When the report appears, sort the list by "Apple Provided" and then list here the ones that either say "No" or "Unknown." Optionally you can try removing them from their respective extensions folders (you can see the path in the top-right of the window) and then restart the system to see if that helps. You can do this one at a time to better specify which ones, if any, are the root of the problem.


More Like This

  • Retrieving data ...

Bookmarked By (0)


  • This solved my question - 10 points
  • This helped me - 5 points
This site contains user submitted content, comments and opinions and is for informational purposes only. Apple disclaims any and all liability for the acts, omissions and conduct of any third parties in connection with or related to your use of the site. All postings and use of the content on this site are subject to the Apple Support Communities Terms of Use.