Command line to compare two external drives?

http://stackoverflow.com/questions/...y-trees-how-can-i-find-out-which-files-differ

 

You can use rsync to do this. The options vary depending on what you want to check. If you just want to verify that the files are there with the right dates et al, you could use this:

rsync -nav /Volumes/disk1/ /Volumes/disk2

It will print out a list of things on disk 1 that do not match disk 2.

n.b.: the trailing slash on the first volume is important, do not leave it out.

If you want to read all the files and checksum their contents, add the -c switch. This will take a long time.

A.