Re: dd if=/dev/rdisk12 of=/dev/zero (OT, since macOS)

The dd is working on the character device, not block device.
I tried it out on a CD on my Mac right before:

cr--r-----  1 root   operator        0x1000032 Nov  2 11:35 rdisk14s0
cr--r-----  1 kuku   operator        0x1000031 Nov  2 11:35 rdisk14
br--r-----  1 root   operator        0x1000032 Nov  2 11:35 disk14s0
br--r-----  1 kuku   operator        0x1000031 Nov  2 11:35 disk14


e.g: 

Christophs-MBP:~ root# dd if=/dev/rdisk14s0 of=/dev/null bs=2048 count=2
2+0 records in
2+0 records out
4096 bytes transferred in 1.509344 secs (2714 bytes/sec)
Christophs-MBP:~ root# 



> Am 02.11.2025 um 10:21 schrieb Marco Moock <mm@dorfdsl.de>:
> 
> Am 02.11.2025 um 10:09:17 Uhr schrieb Christoph Kukulies:
> 
>> It came to memory again when I recalled that I had a similar problem
>> with the attempt to dump (dd) a CD device. One has to specify bs=2048
>> with CDROMs.
> 
> This is rather strange, as I experienced under Linux that reading block
> devices (CD is character dev in Linux) is possible with a different
> block size from the size the device reports to the storage controller.
> 
> The actual block size of the device might be different from those that
> is being reported to the storage controller, see 512e disks.
> 
> -- 
> Gruß
> Marco
> 
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