If your system does not recognize serial hardware, try disabling modemmanager. 
This software appears to conflict with use of the ports for serial device
control.  


If you are using a USB to serial converter, then you will need read/write access
to /dev/ttyUSB0 or something similar.  You will have this if the device is
operated by a user who has membership in the group to which this device is
assigned.  For example, check

ls -l /dev/ttyUSB0

and if it is "dialout", add this group to your user.

Alternatively, make the device available to the world by 

(1) as root chmod a+rw /dev/ttyUSB0

whenever a USB device converted is inserted or powered on

or

(2) adding a MODE="666" entry to the appropriate line of a rules  file in
/etc/udev/rules.d .  

For example, with an FTDI USB-serial converter in  OpenSuse 11.3, if the file
51-gpsd.rules is present, change it to add MODE="666":

# "FTDI 8U232AM" KERNEL=="ttyUSB*", SYSFS{idVendor}=="0403",
SYSFS{idProduct}=="6001", RUN="/lib/udev/gpsd.sh", MODE="666"


USB serial devices made by FTDI work well with Linux.  Devices from other
manufacturers may not.  If you are using Optec accessories like the filterwheel
or rotator, then only FTDI devices will work with any operating system.  Support
for the converter used in the Paramount is included in the Linux kernel.