Nexus devices use media transfer protocol to transfer files to and from the device. There is no removable storage so you can’t take the card out and copy files from it via a card reader.
In the past I’ve used adb tools to push and pull to my device over USB debugging, however while we wait for nautilus gvfs support to be more reliable, this is what I do now (found online somewhere).
Unplug Nexus device.
sudo yum -y install fuse fuse-libs libmtp simple-mtpfs
sudo wget http://christophersmart.com/files/99-nexus.rules \
sudo udevadm control --reload-rules
Plug in device and look for mtp device.
ls -l /dev/libmtp*
simple-mtpfs ~/nexus && ls -l ~/nexus
Now rsync to your heart’s content
rsync -Pa ~/nexus/DCIM/ ~/Photos/nexus/
fusermount -u ~/nexus