I'm unable to mount a DMG, getting a "no mountable filesystems" error

Solution 1:

I have just had the same problem, with a disk image created by Disk Utility itself. In my case, the disk image is whole disk image, i.e. it contains a bare filesystem, no partition map whatsoever. Neither Disk Utility nor hdiutil attach disk.dmg would work, both complaining about the dreaded "no mountable file systems" issue.

What helped was to mount it from the command line, in two easy steps:

hdiutil attach -noverify -nomount disk.dmg

This only creates the device node. Now run

diskutil list

and note the diskN part of your image, where N is a positive integer.

Finally, to mount the device, do

diskutil mountDisk /dev/diskN

where diskN is the device identifier you determined before.

Note that you are mounting the entire disk, whereas normally you would mount a slice, such as disk0s2.

Be aware that this helps if your problem is with a disk image similar to mine. Nonetheless, it should still work with partitioned disk images, see man diskutil.

Solution 2:

Generally, if you are receiving "No mountable file system", that generally means that the disk image is corrupt or damaged.... Try re-downloading the disk image, or downloading the disk image from within another browser....

I have seen infrequent issues when Firefox has been used to download an disk image. Very uncommon, but it has happened...

Solution 3:

I had the same problem on an AES-128 encrypted dmg containing all of my most essential files, the kind worth spending thousands of dollars to have Drivesavers recover. I couldn't even copy the dmg to another drive (could not be read or written -36). My G4 (yes, I'm old school) is running 10.4.11.

This worked:

1. Booted from external hard drive also running 10.4.11.
2. Used Stellar Phoenix quick recovery to find and recovery the dmg to the external hard drive. All subsequent work was on that copy.
3. Ran that drives OS versions built in Disk Utility.
4. In Disk Utility, went to "File" menu upper left, chose "Open Disk Image".
5. Mounted volume then appears as sub dir of dmg in left column, just as any other volume does from it's hard drive, except greyed out (ie: invisible).
6. I use tinkertool to show all my invisible files, the mounted volume still did not appear on the desktop.
7. Attempted repair using Disk Utility without success.
8. BUT, launched DiskWarrior 4.0 and the mounted volume appeared there as well.
9. Ran directory repair (plain, not scavenge) and at the "Report" stage chose "Preview".
10. DiskWarrior reports new and old versions now appear on dektop.
11. I couldn't see either on my desktop (I had too much garbage there & may have missed it), but opening a new Finder window did show the preview volume in left column.
12. Grabbed my files off that preview volume and copied them to the external drive.
13. Praised everything good and right in the universe.
14. Allowed DiskWarrior to complete the rebuild, which was successful and the repaired volume mounted when finished.

Hope this helps.

Solution 4:

I tried everything as mentioned here, as I too had a similar problem, but had to go a bit further to fully solve my issue.

Problem:

I created an image of my disk using Disk Utility on Snow Leopard. Instead of making sure if the image was created correctly, I went ahead and reformatted the drive. Afterwards, I tried to mount the image but it wouldn't let me verify, scan for recovery and the CRC checksum was wrong. All that, just to remove a stubborn boot sector EFI partition that wouldn't go away. Total nightmare!

Solutions:

I tried creating a new checksum and disc scan for recovery. In some cases that helps, but not with this dmg as it was corrupted from the beginning.

What worked best for me was @simonair's answer; although it didn't mount the image completely, it at least allowed it to show the dmg as a "ghosted" active partition under disk utility as well as a working/retrievable partition disk7 under terminal.

Once it was finally visible, I used "Data Rescue 3" in "Advanced View" mode to also show the dmg for scanning. The simple view only shows internal and external physical drives, it seems.

Click on your name.dmg file/virtual drive and make it do a full scan. Depending on its size, it may take from seconds to hours (mine was over 450GB, took approx 6 hours for "deep scan").

I now have all my documents, projects, backed up software and Aperture photo library restored to the original drive after a whole day of suffering.

Moral of the story:

For important data, forget dmg's as they may backfire. If you must create a dmg, make sure it works before deleting the original data. A full 1:1 backup works best to optical media (CD/DVD/BD) or to an additional internal/external hard drive.

Observations:

Disk Drill and Stellar Phoenix didn't help as much as I thought they would. Data Rescue is worth the money, no contest!

Solution 5:

I also had this problem. In the end, what worked for me was Data Rescue.

What didn't work

I tried to follow the recommendations above and copy the dmg to read/write format. I tried both Disk Utility convert and hdiutil command in the terminal, but in both cases Finder hang in the end of the process and I had to restart the computer (forced restart of Finder didn't help).

What worked

I tried to mount the image within Disk Utility. As said above, this doesn't work, but the image now shows up as a greyed-out name in the left column of Disk Utility. This step is necessary so that Data Rescue can see the broken disk image. Next, launch Data Rescue. With "Quick Scan", Data Rescue found the entire folder structure and I could choose what files to recover. All in all, this took only 2-3 minutes.

Thanks sozuke80 for the Data Rescue tip!

// Niklas