Solution to Invalid command 'PubcookieAppID'

When setting up Pubcookie, you may encounter an "Internal Server Error" in your browser and the following error in /var/log/httpd/ssl_error_log (or wherever you're keeping your SSL error log):

[alert] [client] /var/www/html/foo/bar/baz/.htaccess: Invalid command 'PubcookieAppID', perhaps misspelled or defined by a module not included in the server configuration

This might be a headscratcher for a while, since you've probably been working hard to make sure that your Pubcookie configuration is nice and tidy and your .htaccess file is set up with PubcookieAppID, like this:

AuthType NetID
PubcookieAppID fribble
require valid-user

In fact, Apache is telling you exactly what you need to know: it can't make sense of the PubcookieAppID directive because the module that interprets that directive is not loading and thus is "not included in the server configuration."

To solve this, make sure that a line like this is actually somewhere in your configuration, normally somewhere like /etc/httpd/conf.d/pubcookie.conf:

LoadModule pubcookie_module modules/

In my case, I had commented it out while getting SSL to work. Duh.