아파치 에러(mod_passenger unixd_config) 처리

에러내용
$ /etc/apache2# service apache2 start
 * Starting web server apache2                                                                                  *
 * The apache2 configtest failed.
Output of config test was:
apache2: Syntax error on line 140 of /etc/apache2/apache2.conf: Syntax error on line 1 of /etc/apache2/mods-enabled/passenger.load: Cannot load /var/lib/gems/1.8/gems/passenger-4.0.46/buildout/apache2/mod_passenger.so into server: /var/lib/gems/1.8/gems/passenger-4.0.46/buildout/apache2/mod_passenger.so: undefined symbol: unixd_config
Action 'configtest' failed.
The Apache error log may have more information.

원인
Apache 2.4에서 unixd_config 이름이 ap_unixd_config 로 변경됨

해결방안
아래 바이너러를 설치하고 아파치 실행
$ apt-get install libapache2-mod-passenger

또는
./bin/passenger-install-apache2-module로 모듈 재컴파일