[zack@pongo ~]$ gphoto2 --get-all-files
                                                                               
*** Error ***              
An error occurred in the io-library ('Could not find the requested device on the USB port'): Could not find USB device (class 0x6, subclass 0x1, protocol 0x1). Make sure this device is connected to the computer.
*** Error (-52: 'Could not find the requested device on the USB port') ***       

For debugging messages, please use the --debug option.
Debugging messages may help finding a solution to your problem.
If you intend to send any error or debug messages to the gphoto
developer mailing list <gphoto-devel@lists.sourceforge.net>, please run
gphoto2 as follows:

    env LANG=C gphoto2 --debug --debug-logfile=my-logfile.txt --get-all-files

Please make sure there is sufficient quoting around the arguments.