Mavericks apache2 issue after Server 3 removed

After remove Server.app, my apache2 on Mac OS X 10.9.2 Mavericks couldn’t start normally while everything looks OK. After carefully studied the log file through Console.app and looked into the content of /usr/sbin/apachectl, I realized that the starting process of apache in OS X is quite different than that in Linux: it uses launchctl!

So, I searched the apache launchctl config file:/System/Library/LaunchDaemons/org.apache.httpd.plist. Aha! it said:

    <key>SERVER_INSTALL_PATH_PREFIX</key>
    <string>/Applications/Server.app/Contents/ServerRoot</string>
    ......
    and
<key>ProgramArguments</key>
<array>
    <string>/usr/sbin/httpd</string>
    <string>-D</string>
    <string>FOREGROUND</string>
    <string>-f</string>
    <string>/Library/Server/Web/Config/apache2/httpd_server_app.conf</string>
</array>

The key SERVER_INSTALL_PATH_PREFIX and ProgramArguments were modified by Server.app aparently. Just recover them to /usr and /etc/apache2/http.conf, there, it works again!