If you are trying to configure Apache, it can be handy to see what Apache modules are enabled Ubuntu. Here is how to check which apache modules are enabled/installed.
apache2ctl -M
This will provide a list the apache modules which are enabled like so:
Loaded Modules: core_module (static) so_module (static) watchdog_module (static) http_module (static) log_config_module (static) logio_module (static) version_module (static) unixd_module (static) access_compat_module (shared) alias_module (shared) auth_basic_module (shared) authn_core_module (shared) authn_file_module (shared) authz_core_module (shared) authz_host_module (shared) authz_user_module (shared) autoindex_module (shared) deflate_module (shared) dir_module (shared) env_module (shared) expires_module (shared) filter_module (shared) mime_module (shared) mpm_prefork_module (shared) negotiation_module (shared) php5_module (shared) rewrite_module (shared) setenvif_module (shared) socache_shmcb_module (shared) ssl_module (shared) status_module (shared)