I have a 64 gb SD card that is starting to have problems. I want to duplicate as much of it as I can. Is DD the safest/best option to deal with failing sd cards?
I would use
I'd suggest looking up https://help.ubuntu.com/community/DataRecovery for more information, and especially note the caution:
You should NOT write to the failed device, as it can worsen a hardware failure, and overwrite existant data in case of lost files .
(it's covered in the Imaging a damaged device, filesystem or drive section)