Okay, I found the answer to my problem. Mounting an USB drive on OSX which is formatted as Fat32, will not behave nicely when being accessed through samba. Trying to start multiple copy processes simultaniously will cause seemingly random “file locked” errors. I just formatted the drive as HFS+, and the problem dissapeared. This is a screenshot you’d expect when copying, but I was very happy to see it just a minute ago:
Now that I’ve cleared that problem, I can start working on the backup and virusscanning processes, and writing a nice “how to” so you can do the same with your mac mini!
I should have done this right away like I planned. HFS+ is far better than Fat32 (journalled, auto-defragmenting, case preserving, and better in preserving file integrity).