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.