4.1.1.2 krb5.conf

The krb5.conf file contains Kerberos configuration information, including the locations of KDCs and admin servers for the Kerberos realms of interest, defaults for the current realm and for Kerberos applications, and mappings of hostnames onto Kerberos realms. Normally, you should install your krb5.conf file in the directory /etc. You can override the default location by setting the environment variable KRB5_CONFIG.

The krb5.conf file is set up in the style of a Windows INI file. Sections are headed by the section name, in square brackets. Each section may contain zero or more relations, of the form:

     foo = bar

or

     fubar = {
             foo = bar
             baz = quux
     }

Placing a `*' at the end of a line indicates that this is the final value for the tag. This means that neither the remainder of this configuration file nor any other configuration file will be checked for any other values for this tag.

For example, if you have the following lines:

     foo = bar*
     foo = baz

then the second value of foo (baz) would never be read.

The krb5.conf file may contain any or all of the following sections:

libdefaults

Contains default values used by the Kerberos V5 library.

login

Contains default values used by the Kerberos V5 login program.

appdefaults

Contains default values that can be used by Kerberos V5 applications.

realms

Contains subsections keyed by Kerberos realm names. Each subsection describes realm-specific information, including where to find the Kerberos servers for that realm.

domain_realm

Contains relations which map domain names and subdomains onto Kerberos realm names. This is used by programs to determine what realm a host should be in, given its fully qualified domain name.

logging

Contains relations which determine how Kerberos programs are to perform logging.

capaths

Contains the authentication paths used with direct (nonhierarchical) cross-realm authentication. Entries in this section are used by the client to determine the intermediate realms which may be used in cross-realm authentication. It is also used by the end-service when checking the transited field for trusted intermediate realms.

If you are not using DNS TXT records, you must specify the default_realm in the libdefaults section. If you are not using DNS SRV records, you must include the kdc tag for each realm in the realms section. To communicate with the kadmin server in each realm, the admin_server tag must be set in the realms section. If your domain name and realm name are not the same, you must provide a translation in domain_realm. It is also higly recommeneded that you create a [logging] stanza if the computer will be functioning as a KDC so that the KDC and kadmind will generate logging output.

An example krb5.conf file:

     [libdefaults]
         default_realm = ATHENA.MIT.EDU
     
     [realms]
         ATHENA.MIT.EDU = {
         	kdc = kerberos.mit.edu
         	kdc = kerberos-1.mit.edu
         	kdc = kerberos-2.mit.edu
         	admin_server = kerberos.mit.edu
         {
     
     [logging]
         kdc = FILE:/var/log/krb5kdc.log
         admin_server = FILE:/var/log/kadmin.log
         default = FILE:/var/log/krb5lib.log