After a long day working on an upgrade, I realized I needed to adjust the permissions of directories and files that were owned by nobody.nobody.
I was about to send a ticket to the hosting company, when I realized you can use PHP to change the permissions, and invoke the script through the browser.
It wasn’t graceful, or efficient, but, it did let me change permissions and continue.
The real lesson is to wait until the last minute to ask the hosting company to change ownership of the files. I hurried, because the server was hacked when I logged in.