A user filed SERVER-17977 after modifying the configuration files that come with packages and not being able to remove or upgrade the packages.

They said we should add a note to http://docs.mongodb.org/manual/reference/configuration-options/.

We could mention that Linux packages come with included configuration files and modifications to them should be made carefully or upgrading and removing processes won't work.

We could also specifically call out the fork, log path, and db path options, which will be especially problematic if people change them.