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Re: need sd card backup on r-pi-3b

On Fri, 2017-09-22 at 22:07 -0400, Gene Heskett wrote:
> Greetings;
> Trying to dd a copy of the micro-sd card the pi-3b is booting from, to 
> another micro-sd card in a usb reader/writer, and winding up with 
> nothing but an empty lost+found directory on it.
> Obviously some sort of a syntax error, but it still takes the pi several 
> hours to do it, with the traffic led on the reader/writer showing 
> continuous activity.
> Is there another way/util that actually works for making verbatim backups 
> of these limited lifetime sd cards?
> Thanks.
> Cheers, Gene Heskett

I used to use dd quite a lot, usually to a file (from a disk) as I was
playling with virtual boxes quite a bit. It "may" be that the dd is not
from the disk, but is from a partition... or some other variation on the
theme (1). Also, its worth typing sync after the dd to make sure that
all disk access (write) is coalesced. If I recall correctly, once the
sync returns to the command line then there are no more pending writes
so even pulling the SD (not correctly un-mounting/ejecting it) shouldn't
corrupt it. 

(1) When dd'ing between physical drives I always made sure they were
matched size wise, which was probably not required but I had it in my
head that dd'ing a drive including the partition table to a larger sized
drive would cause issues. Where the drives were unmatched I'd set the
new partition(s) manually, and then dd the partitions one at a time and
I always made sure the too partition was set up to be the same size as
the from partition (even if the location differed) and then do any
re-sizing of the cloned partition & file system upwards afterwards. As I
say, possibly not required in some/all cases but gut feelings are hard
to overcome as I had it in my head - something to do with backup tables
set at the far end of partitions.

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