OSX: can I dd a usb thumb drive into a file?

Question

I have mounted a usb thumb drive into my MBP.

Here is the partial output from mount

/dev/disk2s1 on /Volumes/KINGSTON (ntfs, local, nodev, nosuid, read-only, noowners)

When I tried

$ dd if=/dev/disk2s1 of=usb.img bs=512
dd: /dev/disk2s1: Resource busy

It seems like 'Resource busy' error prevent me from using dd on the thumb drive.

Is there any solution?

Answer 1

Use Disk Utility to unmount the drive, and possibly also to do the copy; this has the advantage that you can mount the image afterward if you need to get at any files in it. If you prefer the command line, hdiutil is the command line version of Disk Utility.

Answer 2

Unmount the volume after you learn its device, then repeat.

Answer 3

Maybe unmount usb drive first and then rerun dd?