Honey, I broke the server

Here's how I caused 25 minutes of downtime to my web server today.

Upon restart of the http deamon, Apache runs an action called configtest, which parses all files in conf.d/ the name of which ends in .conf, and decides if they are valid configuration files. This is defined in your server's configuration file, in a line that should be something similar to:

Include conf.d/*.conf

What I didn't know was that the server will refuse to start altogether, if it doesn't like an instruction in those files, so, not only had I placed textfiles in that folder that were not valid apache config files, but at some point I recommended this to others also. In my case, the files were combinations of credentials used for authentication by .htaccess rules, files produced with htpasswd.

The problem only came up when I restarted httpd to enable new configuration elsewhere. Of course Apache offered a useful explanation (where USERNAME and aSdFG123456ASdFG are the username and the hashed password used for access by .htaccess):

Invalid command 'USERNAME:aSdFG123456ASdFG', perhaps misspelled or 
defined by a module not included in the server configuration
Action 'configtest' failed.
The Apache error log may have more information.

It seemed like a logical and convenient place to put the credentials' files upon creation, but it made apache refuse to launch, because I had the inspiration to name those files something.conf. I checked some older web servers, with prehistoric versions of apache -some 5 years old- and I estimate that this is not an issue for those versions, I assume that maybe older versions of Apache ignored unknown instructions and started anyway.