Do your clients know which server software their site runs on?

When a security issue hits something like the PHP version or a plugin, the first question is always which version a given site is running. In my experience many small business owners cannot answer, and sometimes the person who built the site cannot either, because hosting was set up years ago.

A simple list of each site with its host, PHP or runtime version and last update date would answer it in a minute. But it only works if someone keeps it current.

Do you keep that kind of inventory for your own products or your clients' sites? How do you keep it up to date, and who is responsible when a version reaches end of life?