Some possible solutions to this problem:
i) Check if .htaccess file is making any redirections
ii) Check if /LocalSettings.php have any invalid reference to root
ii) If you have freshly installed the server, check if AppArmor or SELinux is installed on the machine. If it is try to remove those software and try you website url.
To remove appArmor follow the below steps:
$ /etc/init.d/apparmor stop
$ update-rc.d -f apparmor remove
$ apt-get remove apparmor apparmor-utils
