Install "libapache-mod-auth-kerb" - of course you'll also need apache setup and this article assumes you've already got kerberos setup as it's discussed here. One example of how you can take advantage of Kerbose & Apache in a case like this is to enable authentication with your Active Directory server.
sudo apt-get install libapache-mod-auth-kerb
You need to setup a kerberos keytab, put it where ever, I put mine at /etc/krb5.keytab.
This file should contain a line of the form HTTP/replace_your_web_server_full_hostname_here@ACTIVE_DIRECTORY_FULL_DOMAIN_NAME.
So, to put that another way: HTTP/www.mydomain.com@MYDOMAIN.COM
In whatever sections of your Apache VirtualHosts (or just apache config if you're running only one site), you want to add lines of the following form:
AuthName "Kerberos Login" AuthType Kerberos Krb5Keytab /etc/krb5.keytab KrbAuthRealm EXAMPLE.COM KrbMethodNegotiate off KrbSaveCredentials off KrbVerifyKDC off Require valid-user
sudo /etc/init.d/apache restart
* This article borrows heavily from here.