Cloning a multi-partition hard drive

Question

Cloning a multi-partition hard drive

Is it possible through either Terminal or Disk Utility, or even a third party app to clone an entire hard drive that has several partitions to a second same-size hard drive? I've got several TB and want to back everything up at one go rather than doing a Finder copy of each partition, three of which have different versions of MacOS necesitating tge use of something like CCC. I want to set it and forget it, letting the operation run overnight unattended.

Thanks.

Mac mini, macOS Sierra (10.12.4), 10GB SDRAM 740 GB fusion drive

Posted on May 7, 2017 11:39 PM

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Answer 1

May 8, 2017 3:37 AM in response to TodFromIndiana

I am not aware of any GUI based tools that offer this feature but can suggest one possible approach. It would I feel only have a change of working if both drives are identical sizes and preferable identical models as well. (Which in your case seems a possibility.)

There is a command-line tool called dd which stands for disk duplicate presumably. Normally one uses it to duplicate an individual partition but you can specify the entire drive as well.

Here is the command to copy an example individual 2nd partition to another individual 2nd partition -

sudo dd if=/dev/disk0s2 of=/dev/disk2s2 bs=128m conv=noerror,sync

Here is the equivalent command to copy the entire drive -

sudo dd if=/dev/disk0 of=/dev/disk2 bs=128m conv=noerror,sync

Some people suggest using the /dev/rdisk variants rather then the above /dev/disk speeds things up, also adjusting the block size might also speed things up. I think most people would consider /dev/disk to be the 'safer' form as it uses the operating system caching feature and also auto handles sector alignment issues.

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Answer 2

May 8, 2017 2:04 PM in response to John Lockwood

@ John, thanks for the very detailed and informative reply. You are right about the drives I am using: I bought a Seagate from Amazon last week and I was impressed with its performance that I decided to order another identical drive to use as a backup of the first drive. In addition to having partitions for 10.10, 10.11, and 10.12, I have one for games, one for movies/videos, one for photo editing and storage (tens of thousands of 35mm slides and negs being digitized), and another for a couple of large DevonThink databases.

I won't be able to try your solution until Friday, when the new drive arrives. At that time I'll report on how it worked (fongers crossed!).

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