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I just plugged in a microsd and doing a diff before and after

   ls -l /dev/ > before   
   ls -l /dev/ > after

these 4 new devices show up:

  1. /dev/disk1
  2. /dev/disk1s1
  3. /dev/rdisk1
  4. /dev/rdisk1s1

I understand that disk1s1 could be one a partition of disk1 but what is rdisk1 ? another partition ?

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/dev/disk1 is the raw block device. /dev/disk1s1 is a partition of the device if it had more partitions you would also see /dev/disk1s2 and disk1s3 and so on.

You would use /dev/disk1sN (N is the partition you are interested in) if you are going to manually mount or unmount a partition. You would use /dev/disk1 if you are going to dump something to or from the device. For example, you could

sudo dd bs=8k if=/somefile.iso of=/dev/rdisk1 

or dd bs=8k if=/dev/rdisk1 of=./image_of_drive.iso The /dev/rdisk* I think are buffered versions of /dev/disk* I am not sure, but you can read or write to disk1 or rdisk1 interchangeably

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I got rdisk and disk backwards. rdisk is the raw device disk is the buffered block device – Kyle-Euclid Jun 15 '13 at 17:13

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