On 24/07/2018 02:59, Henri Derksen wrote:
> A new quirk from Rasbian Stretch (necessarry for a Pi 3B+)
> is that you cannot read a 100 % backup of a SDCard of the same size.
> At older versions of Raspbian (Jessie/Wheezy) this was no problem.
> First I thought my SDcards or reader/writer were defective.
> Then I remarked I could read a 16 GB backup SDcard when booted from
> a 32 GB Raspbian Stretch OS. The other way round also worked.
> But I can not read a 100 % 16 GB backup when booted at a 16 GB card.
> The same happens to a 100 % 32 GB backup when booted from a 32 GB card.

What do you mean by 'read'? Do you mean using dd to /dev/null, or using
dd to copy it on the card the machine has booted from? I'd be very
surprised if the former failed, and you should not be doing the latter,
as writing to a running image will cause it to be corrupted.

When copying between cards, it is common to find that no two of the same
stated capacity have exactly the same number of sectors, and you can't
perform an exact copy from a larger card to a smaller one.

To get around this, after setting up an Pi image and allowing it to
expand to the size of the card, I then remove it and use gparted to
shrink the last partition by 1M. This means it can safely be copied to a
slightly smaller card without losing anything vital. Note this may not
be possible with the NOOBs card layout, which is why I avoid it.

---druck

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