Ubuntu 10.04 and Sprint 3G/4G

The instructions are here:

http://jebus.nu/tech-corner/sprint-u300

You can probe your USB devices and see which one has a CMOTECH, a South Korean company that manufactures eVDO data modems.

# lsusb
Bus 002 Device 008: ID 16d8:6008 CMOTECH Co., Ltd. 

Unlike the link, the product ID was 6008. So I used the following command to add the unit as a serial device:

sudo modprobe usbserial vendor=0x16d8 product=0x6008

The /etc/udev/rules.d/50-u301modem.rules looks like:

ACTION!="add", GOTO="3G_End"

SUBSYSTEMS=="usb", ATTRS{idProduct}=="6008", ATTRS{idVendor}=="16d8", RUN+="/sbi
n/modprobe usbserial vendor=0x16d8 product=0x6008"
LABEL="3G_End" 

Note: for Ubuntu 12.04, you don't need to make these changes. In fact, you shoud remove the rules, sudo service restart udev, and restart Gnome (logout).  Ubuntu 12.04 already seems to have rules for these modems (at least the U600 device), and having this rule appears to conflict with the Mobile Broadband option that gets provided.