Copy new files only - is this possible? Basically want to merge two folders I have a folder on Drive 1 called Music, and it is 100GB. I have a folder on Drive 2 called Music, and it is 116GB. It's the most updated version. How do I copy the Music folder from Drive 2 to Drive 1 without having to rewrite every single file?
This is a classic use case for rsync:

rsync -av /source-path/source-dir /destination-path


rsync will copy only new and changed files to the new location.

It is important to understand how a trailing slash on the source argument functions.  If there is a trailing slash then the contents of /source-path/source-dir will be copied to destination-path.  If there is no trailing slash then source-dir itself will be copied to the destination and its contents will be another level down in the destination hierarchy.

So if you want to replicate one path to another include the trailing slash as follows:

rsync -av /sourcepath/sourcedir/ /duplicatpath/sourcedir/