If you already have a Deployment Server up and running, the simplest way of getting this is probably to install the forwarder on an HP-UX machine and set it to contact the Deployment Server.
On the server you could then run splunk list deploy-clients, or check in the Deployment Monitor under the 'All forwarders' view.
The actual value is not controlled by Splunk, as the OS of the forwarding host supplies this string.
From the serverclass.conf documentation
# The value for machineTypes is a specific string that is designated by the hardware platform itself.
# The method for finding this string on the client itself will vary by platform, but if the deployment client
# is already connected to the deployment server, you can determine what this string is by using this
# Splunk CLI command on the deployment server:
# <code>./splunk list deploy-clients</code>
# This will return a value for <code>utsname</code> that you can use to
# specify <code>machineTypes</code>.
hope this helps,
Kristian
