Connecting Cognos 8.3 to Informix 11.5 on Linux via ODBC

Download the Informix ClientSDK from IBM's website

On the server side (ubuntu) make sure that a service is created with the IP/port/protocol in the file is specified under SQLHOSTS environment variable
Add the service to /etc/services specifying port/protocol
Start informix
$oninit
from the logon specified in the ODBC connection. No startup error messages should be displayed
Adding the ubuntu logon to the informix group (created at install time) solves quite a few problems.

Installing on Windows Installation of the CSDK is straightforward :
Extract the contents of the downloaded zip file
The installer creates an entry IBM Informix Client-SDK 3.50 under 'All Programs'
From there, it is easy to access Setnet32 to create the ODBC connection

Run setnet32:

Select the Host Information tab and under
Server Information enter the connection parameters :
Database : database
Host name: Host IP
Server: INFORMIXSERVER that is set on the linux server
Protocolname: onsoctcp (or whatever protocol specified for the service in sqlhosts)
Service: port (service specified in /etc/services file or the port number)

Under the Host Information tab:
Current Host: Host IP
Username: ubuntu logon
Password Option: Specify if a password is required
Password: Enter the ubuntu userid password

On the server side:
Update the sqlhosts file with the service name
Edit /etc/services to include the service IP/protocol and port numbers

Test the connection and then Save the connection under a name such as informix115
You can now use the saved connection wherever an ODBC connection is allowed