I'm finding multiple answers to the question, so wanted to ask people that actually use it, rather than just want to make the biggest blog by filling out with random semi useless information.
rsync -av --progress /dir/a /dir/b
and it does its thing.
I add new files to /dir/a and run the same command again, it knows what it did and only copies the new files.
I add new files to /dir/a and rename some files in /dir/b, and maybe delete a few too.
If I run
rsync -av --progress /dir/a /dir/b again, what will be copied? Just the new files because it knows what it has previously copied, or the files that were renamed/deleted ones too, because they are no longer present.
And as a bonus, if the previously copied files are copied again, is there a way to prevent that, so that only new additions to /dir/a are copied?
At the moment I'm happy checking things manually, but as the data gets bigger I'm going to need more automation to perform this task.