I moved my Splunk instance to another machine and I'm getting the following error message: 2010-06-15 16:20:24,739 ERROR [4c17e085c52d202e8] parser:103 - Error in 'script': Getinfo probe failed for external search command 'diff'. How do I get this script to execute correctly?
Sounds like you may have a problem after your migration. The diff.py is an internal command in the search app that should work out of the box.
I took a quick look at that script on my 4.1.2 install and diff.py does call splunk.Intersplunk.isGetInfo and commands.conf is set accordly with supports_getinfo = true. So I suspect that you have a out-of-sync install. I'm guessing you will continue to find other components that that may not be working properly anymore.
Have you tried re-installing the latest version overtop of your install. I suspect that would replace these built in components and get them working again. That's just a thought.
You may also want to add to your question the details of your migration process. Specifically, did you move across platforms, did your install path change between systems, and so on.