@Jonathanta I used scp to copy them over the network. We have a MacBook Pro, and an old Dell laptop that runs Linux.
scp comes installed with ssh. I installed an ssh server on the Linux laptop, which allows me to log into it via the Terminal. It also allows me to copy files back and forth securely.
Syntax example: scp /some/directory/on/your/mac your_username@192.168.10.1:/some/directory/on/linux/box
Change the IP address (192 etc) to whatever the IP address is for your Linux box. On your local network, it will probably either start with 10 or 192, depending on your router.