I'm new to Linux, and looking to completely replace Windows for most of my machines. Elementary is the first linux flavour I've really loved. One thing I can't find an alternative to is a program called Unstoppable Copier by Roadkil (their linux version is way old and out of date). What I used it for is backing up my two NAS file servers (each 4TB) to offline USB drives. The cool thing it does is sequentially copies large numbers of files, skipping those that already exist on the target. If it gets interrupted it can restart from where it stopped. Can anyone recommend a program to do this on Linux, or help me with the command line to achieve the same thing? Thanks in advance.