This is optional, but makes things more convenient…

udev rules

create a file /etc/udev/rules.d/90-smoothie.rules and add the following to it…

SUBSYSTEM=="usb", ATTRS{idVendor}=="1d50", ATTRS{idProduct}=="6015", MODE="0666"
SUBSYSTEM=="tty", ATTRS{idVendor}=="1d50", ATTRS{idProduct}=="6015", SYMLINK+="smoothie%n"

when you've done that, you need to reload the udev rules in order to get them working.

udevadm control --reload-rules
or
sudo service  udev restart # ubuntu

Under fedora, smoothieboard is handled by the modem manager (as an openmoko).
To avoid this , add in the udev rule :

ENV{ID_MM_DEVICE_IGNORE}="1"

Then plug in Smoothie, and it should appear as /dev/smoothie0
If you have two USB serial devices configured the second one will be /dev/smoothie1

TODO : The distribution specific sections need to be verified for other distributions

Fedora, Ubuntu, Debian and derivatives

If you want to be able to talk to the /dev/smoothie0 with your regular non-superuser login then you need to add your user to the dialout group.
To be able to flash via DFU as a regular user then add the user to the plugdev group too
This can be done either with.

sudo adduser <username> dialout
sudo adduser <username> plugdev

or

sudo vigr

and add the username to the end of the line for dialout and plugdev

Arch

To be able to talk to the smoothie on Arch linux you need to be in the uucp group.

usermod -a -G uucp <username>

where <username> is the name of your user

To be able to upload firmware using make upload without the need of using sudo, you need the udev rule shown above.
It sets the permissions for all users to rw (0666).

PID problems

If your PID and VIDs are 0000, take a look at this forum post.