Tools/tips to recover data from a corrupt DMG disk image?

Question

Please share, if you know any tips to salvage data from a "compressed DMG" which no longer mounts (in my case, something went wrong during "scan image for restore").

Answer 1

Answering my own question here with a list of things to try.

• Disk Utility > First Aid > Repair Disk
• Disk Utility, try converting the image to an ISO
• try using 3rd party utility to convert the image, such as "dmg2iso" (sometimes this has a side effect of ignoring corrupt data, and the image will mount)
• try mounting with 3rd party utility such as Toast
• hdiutil attach -ignorebadchecksums /Volumes/path/to/image
• hdiutil mount -nomount -readwrite /Volumes/path/to/image (then try repair using DiskWarrior, etc)

I'll probably be fleshing this list out over the next week as I do more research. I want to take a look through these sites:

• http://discussions.apple.com/thread.jspa?threadID=1218394
• http://discussions.apple.com/thread.jspa?threadID=2065256
• http://lorenzo.yellowspace.net/corrupt-sparseimage.html

Answer 2

DiskWarrior can be used to rebuild some corrupt disk images, depending on the nature of the corruption. Might be worth a shot if you have a copy.

Answer 3

I had to use the -noverify and -mount suppressed flags to get my disk to mount. Without those flags, the errors kept causing the mount to abort. After mounting in this way, I was able to select a blank entry in the Disk Warrior drop-down and recover the majority of my files.

hdiutil attach -noverify -mount suppressed /Volumes/path/to/image

Answer 4

Most probably, it is dead beyond repair.

You will need to download or obtain it again.