I need to add to the PATH environment variable used by Splunk Universal Forwarder.
I have tried editing splunk-launch.conf and I have checked the envvars using splunk envvars
but this doesn't seem to set the path.
Is it possible to set the PATH variable that Splunk uses?
(Note, I only want to setup this specialized PATH for the splunkd instance. I do not want it to be systemwide)
Why do you think that you need to do this? I have never had to do any such thing.
because I need to have splunk call a specific python interpreter. The system has python 3 installed. I need to install python 2, and set the PATH so that SUF calls python 2.
If that is truly necessary, several people have indeed made changes like this. You should ask for exactly that, namely "How do I configure my Splunk app so that it uses a different Python version installed outside of Splunk" or some such. You have far, FAR more likely to get a response to such a question.