/etc/freeradius/modules/krb5 is in freeradius 2.2.8+dfsg-0.1build2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
| 1 2 3 4 5 6 7 8 9 10 11 | # -*- text -*-
#
#  $Id$
#
#  Kerberos.  See doc/rlm_krb5 for minimal docs.
#
krb5 {
	keytab = /path/to/keytab
	service_principal = name_of_principle
}
 |