Yesterday one of our team changed the permissions on /sites/default. I'm not sure exactly what permissions he set, he said he turned on write and execute with his ftp client but didn't say exactly what change mode he used. Looks to me like he changed it to write and execute with no read. Then he said he removed write and execute. Then he tried to deactivate install.php by renaming it because the site now showed the install page instead of the site we've been building. The result was when you went to the home page, there was a notice that said we were in a loop.
So I went in and changed all the permissions to match a test installation that was working, 0755 for /sites/default, and 0644 for settings.php and 0775 for /sites/default/files, and restored the install.php fie to its proper name. The result was that the site came back.
From this little exercise, I came up with some questions about how, exactly, does Drupal deliver the website. I see that index.php executes bootstrap.php, and bootstrap.php is in charge of delivering everything. How does bootstrap.php decide whether or not to go to install.php? Looks to me like install.php came up because settings.php was changed so that it was not readable any more.
Now that everything is back, should we delete install.php?