From logs:
[Tue May 05 10:01:46.317409 2015] [authz_core:error] [pid 5837] [client 109.70.215.137:32407] AH01630: client denied by server configuration: /var/lib/roundcube/
From browser:
Forbidden
You don’t have permission to access / on this server.
To enable roundcube on Debian 8 after an upgrade add the following “Require all granted” to a virtual host configuration file:
<Directory /var/lib/roundcube/>
Options +FollowSymLinks
AllowOverride All
Order allow,deny
Allow from all
Require all granted
</Directory>
Access control
In 2.2, access control based on client hostname, IP address, and other characteristics of client requests was done using the directives Order, Allow, Deny, and Satisfy.
In 2.4, such access control is done in the same way as other authorization checks, using the new module mod_authz_host. The old access control idioms should be replaced by the new authentication mechanisms, although for compatibility with old configurations, the new module mod_access_compat is provided.
Here are some examples of old and new ways to do the same access control.
In this example, all requests are denied.
2.2 configuration:
Order deny,allow
Deny from all
2.4 configuration:
Require all denied
In this example, all requests are allowed.
2.2 configuration:
Order allow,deny
Allow from all
2.4 configuration:
Require all granted
In the following example, all hosts in the example.org domain are allowed access; all other hosts are denied access.
2.2 configuration:
Order Deny,Allow
Deny from all
Allow from example.org
2.4 configuration:
Require host example.org
More infromation:http://httpd.apache.org/docs/trunk/upgrading.html