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jobborrow 02-13-2010 05:30 PM

Corrupted DMG files on external drive...

I have an external drive where I store loads of stuff, one of the things I store there is lots of apps, some of which I can get again. However, there are a few that will be hard to get again and I also had some really good NFR software there I want to use. It all worked at one point, but now if I try and mount a DMG file it says "image data corrupted unable to mount disc" (or something).

Is there anyway to recover these dmg files? I have no idea what could have happened to the data on my external drive, I don't remember the drive being dropped or anything. If I drag a new dmg file to the drive and then try it, it works.

I tried checking the disc in the disc the utilities and running a repair, that doesn't help.

Thanks for any help.

chscag 02-13-2010 06:28 PM

It sounds like that external drive has problems. Use Disk Utility to check the drive. Mount the drive, open DU, click on the First Aid tab and do a verify and repair. If the drive shows a lot of errors, don't use it any more as it's probably getting ready to die.

Just a suggestion: If you need to archive programs or files, a better way would be to burn them to DVD media. Hard drives fail, even good ones. CD and DVD media are not 100% fool proof either, but they'll outlast a hard drive. I have old files archived on CDs and DVDs from 10 years ago and I can still open them or copy them. I'm a pack rat. :)


jobborrow 02-13-2010 06:42 PM

Thanks for the reply. I tried to do a full repair, it says the disk appears to be fine, it has a Mac area and a windows partition (FAT). The strange thing is all my files that aren't dmg file are perfect, for example I have some websites stored on there, html pages etc and some word documents and some pdfs and they are all fine, the only things that are corrupted are all my dmgs, very strange... So there's no way to recover them? There's nothing to indicate that the disc is dying....

chscag 02-13-2010 08:52 PM

No way to recover a DMG file that I know of. DMG files are compressed which makes recovery more difficult than say a corrupt document. If possible, try to download them again. And yes, it is strange that only the DMG files are corrupt and not the others. I'm wondering if they were somehow damaged when you copied them to the external drive. I have had that happen to me with large image files.


jobborrow 02-13-2010 09:04 PM

Maybe that's what happened. Really annoying. I will have to seek out all the apps again, most won't be a problem. Just annoying. I guess the moral of the story is; once uploaded and back up, check your DMG files from the drive to make sure they're working before deleting everything you thought you had saved.....

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