Problem with dd and /dev/sr0

[jd1008]

On 03/14/2016 11:17 AM, Rick Stevens wrote:
> On 03/14/2016 10:11 AM, jd1008 wrote:
>> Hi all,
>> time dd if=/dev/sr0 of=Our_Group_Picnic.iso bs=64M skip=5888
>> conv=noerror,notrunc oflag=append
>> dd: ‘/dev/sr0’: cannot skip: Invalid argument
>> 0+0 records in
>> 0+0 records out
>> 0 bytes (0 B) copied, 0.000301689 s, 0.0 kB/s
>>
>> but
>>
>> {3464-jd at localhost}$ time dd if=/dev/sr0 of=Our_Group_Picnic.iso bs=64M
>> conv=noerror,notrunc
>>
>> works just fine.
>>
>> So why is it that skip des not work on optical media?
>
> Skip works fine, but you must specify the units. "skip=5888" doesn't
> tell dd how far to skip. E.g. "skip=5888c" would skip 5888 bytes. From
> the man page:
>
>     N and BYTES may be followed by the following multiplicative
>     suffixes: c=1, w=2, b=512, kB =1000, K=1024, MB=1000*1000,
>     M=1024*1024, xM=M  GB=1000*1000*1000, G=1024*1024*1024, and
>     so on for T, P, E, Z, Y.
I thought that bs=64M  applies to all io for input and output, and skip.
I did not specify ibs= nor obs=, just bs=