On 10/01/2019 08:18, Jan Panteltje wrote:
> Henri Derksen wrote in
>> You forget two important things, i.e. the block size and the Sync !
>> So the two commands should be at least:
>>
>> sudo dd if=/sda of=/dev/sdb bs=1M conv=noerr,sync [RETURN]
>> sudo sync                                         [RETURN]
>>
>
> Not in my uexperience.
> I _do_ use dvdimagecmp to test if the image is the same as the card:

[Snip]

> So far never seen an error with
> dd if=/dev/whatever of=my_new_perfect_image

Omitting block size will still copy the card OK, it will just do it very
slowly and may rapidly degrade life of the card. You will be writing in
512 byte sectors, and the controller may (if it isn't very clever) have
to rewrite an entire flash block of at least 128KB each time. By
specifying bs=1M you will ensure the controller always writes whole
flash blocks, and is much quicker.

Omitting sync normally doesn't cause a problem if removing the card a
second or two after the copy has finished. So it depends if you always
want to do things correctly, or see how long you can get away with
sloppy practice before things go wrong!

---druck

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