I got the following error message after compiling apache against the latest OpenSSL version.
Cannot load modules/mod_fcgid.so into server: undefined symbol: ap_unixd_setup_child
It looks like a compiler error that happened, but it isn’t. In fact, there are two options why there is this error message appears.
One mod_unixd isn’t loaded or loaded after mod_fcgid. Two mod_fcgid can’t create a directory for the socket or the socket itself. aka file permissions.
That error message could be much better. It is misleading. This error does not happen on Windows. It comes from the old Unix philosophy: “Everything is a file”. This lead to a ton of code in the kernels. Even more, code exists for block devices in /dev. All that symlinks and magic directories. I wonder when “Everything is a file” will have exceptions everyone agrees on.