[ale] Initial RSYNC data validation

[attriel]

James Taylor wrote:
> I've got about 500GB of data I need to maintain a sync of across a WAN connection, and RSYNC seems well suited for what I need to do.  However I have not been able to figure out how to establish an initial sync without copying all the data over the first time.
> 
> There must be a switch I can use to do a data compare on an initial sync to establish a baseline.
> 
> Just to be clear, I have a back up of the original data which I restore on the remote site.  I then want RSYNC to know that the files on the remote site are the actual unchanged files that they are comparing from the local site on the initial sync.  I don't want to try to copy all of this across the WAN link.

rsync starts with comparing the files (chunky md5 i think)

i think the -n switch is "don't copy anything, just tell me what you 
would do" so you can try that to see what files it thinks don't match

--attriel