Creating an ISO from unmountable CDR

Question

Level 1

56 points

Creating an ISO from unmountable CDR

I have a CDR with some proprietary data for a legacy hardware sampler. I'd like to create an ISO file from the disk on my Mac since I may just need to refer back to the data in the dim distant future. The CD won't mount on my Mac because it doesn't recognise it. Is there a way of creating a copy of it blind to back it up on my Mac? I used to use Toast to do such things but haven't had a version for a very long time and certainly nothing that will work with Catalina. I tried Disk Utility but that didn't work. I am using a Mac external USB CD drive.

Thanks

Mac Pro, macOS 10.15

Posted on Oct 11, 2020 8:52 AM

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Answer 1

Oct 11, 2020 9:05 AM in response to insch

CD-R doesn’t last forever, and may become unreadable over time. The brand (the factory it came from) also plays a role. Some discs are just crappy and are not archival quality. Exposure to daylight will also reduce the longevity.

Sometimes a different drive can read what other drives can’t. You probably know a few people that may want to give it a go for you.

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Answer 2

Oct 11, 2020 9:06 AM in response to insch

insch wrote:

...The CD won't mount on my Mac because it doesn't recognise it. Is there a way of creating a copy of it blind to back it up on my Mac?...

If it doesn't mount, either the drive is dead or the CD is no longer

functional.

If it is the first case, you need a new drive. If it is the second case,

you can't recover a corrupted/ruined/defunct CD.

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Answer 3

insch Author

Level 1

56 points

Oct 11, 2020 9:46 AM in response to woodmeister50

Just to clarify - my ext CD drive is not dead and I don't believe that the CD in question is damaged or corrupted. I am sure that the issue here is that this is a proprietary disc that a Mac would never have mounted. The disc was formatted for a hardware sampler (an E-mu E6400 to be precise) back in the days of such things. I don't expect to be able to mount this disc on my Mac or for my Mac to make sense of it but many years ago I used to be able to blind copy CDRs and create ISOs of them as a more future proof backup than a physical CDR. I would just like to be able to do that with this CDR. What might be the best way to do a blind copy?

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Answer 4

HWTech

Level 9

55,784 points

Oct 11, 2020 5:21 PM in response to insch

If the CD is proprietary, then it likely includes some type of copy protection which will prevent it from being copied.

As others have noted burned CDs will degrade over time and may not be recoverable.

As for cloning the CD bit for bit you can try using GNU ddrescue since it doesn't require the volume to be mounted. GNU ddrescue is made to try and recover data from failing media so it will make multiple attempts to read the data until it believes it has recovered the data. You will need to install GNU ddrescue using Homebrew. This will only work if the CD is not copy protected. GNU ddrescue is a command line utility.

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Answer 5

Barney-15E

Level 10

112,722 points

Oct 12, 2020 5:26 AM in response to insch

Thank you. So there is no way of just creating a blind ISO of the disc?

Creating anything from the disk requires that it can be read. If it can't be mounted, there is nothing on the Mac that can read it.

If you can find someone with a disk duplicator, that might work, but then it might just duplicate what is wrong with the disk.

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Answer 6

insch Author

Level 1

56 points

Oct 12, 2020 6:12 AM in response to Barney-15E

OK, thanks. I had a way of cloning CDRs many years ago even though they wouldn't mount on my Mac. Maybe that was through Roxio Toast. I can't remember but I have definitely done it - sometimes to have a 2nd copy of an essential disc. Maybe that is not going to be possible now.

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Answer 7

HWTech

Level 9

55,784 points

Oct 12, 2020 9:02 AM in response to insch

insch wrote:

Thank you. So there is no way of just creating a blind ISO of the disc?

GNU ddrescue can perform a bit for bit clone of an unmounted drive. If the CD is not copy protected and is still readable, then it should work. If the CD is copy protected or has degraded, then it is unlikely anything will be able to copy the CD. It is one of the downsides of proprietary media.

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Answer 8

HWTech

Level 9

55,784 points

Oct 12, 2020 9:07 AM in response to Barney-15E

Barney-15E wrote:

Thank you. So there is no way of just creating a blind ISO of the disc?

Creating anything from the disk requires that it can be read. If it can't be mounted, there is nothing on the Mac that can read it.

GNU ddrescue does not need to have a drive mounted in order to make a bit for bit copy (in fact it requires the drive to be unmounted). GNU ddrescue is a much better version of the command line utility "dd". Assuming the CD is not degraded or copy protected, then GNU ddrescue will work. Even "dd" may work, but GNU ddrescue is better as it can try to skip past any read errors and it shows the progress of the transfer. Plus GNU ddrescue clone can be resumed if the logging/mapping file is used.

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