Define the custom information key in Spacewalk as described in Section 10.4.2, “Defining Custom Information Keys Using the Spacewalk Web Interface” and Section 10.4.3, “Defining Custom Information Keys Using spacecmd”.

For example, you could define a custom information key named uptrack-uname to store the value of the Ksplice effective kernel version.

Install the rhn-custom-info package on each client with which you want to use the key.

Use the rhn-custom-info command to make the value of the key available in Spacewalk. For example:

# rhn-custom-info uptrack-uname `uptrack-uname -r`

This command makes the value returned by uptrack-uname -r available as the value of the uptrack-uname key. You can then use the macro rhn.system.custom_info(uptrack-uname) to extract the value of uptrack-name within a configuration file.