rsync

Am I correct in assuming that the following command:

rsync -a /a /b

does not make any changes on /a if there are files on /b that are newer

Shouldn't it be like this?

rsync -a <src> <dst>

I think you want this

rsync -a /b /a

regards,
Ahamed

That's correct, rsync works one way only , source to destination however you should learn to use --list-only option.