Codeigniter+ubuntu

saya buat aplikasi tapi saya ganti os dri win ke ubuntu, tapi aplikasinya gak bisa diakses kalau di ubuntu. output di browser seprti ini

Access forbidden! You don't have permission to access the requested object. It is either read-protected or not readable by the server.

If you think this is a server error, please contact the webmaster.

Error 403 localhost Apache/2.4.18 (Unix) OpenSSL/1.0.2e PHP/7.0.0 mod_perl/2.0.8-dev Perl/v5.16.3

ini kenapa yaa..? padahal gak ada perubahan apapun di aplikasinya