MIT Kerberos Documentation



krb5kdc [-x db_args] [-d dbname] [-k keytype] [-M mkeyname] [-p portnum] [-m] [-r realm] [-n] [-w numworkers] [-P pid_file] [-T time_offset]


krb5kdc is the Kerberos version 5 Authentication Service and Key Distribution Center (AS/KDC).


The -r realm option specifies the realm for which the server should provide service.

The -d dbname option specifies the name under which the principal database can be found. This option does not apply to the LDAP database.

The -k keytype option specifies the key type of the master key to be entered manually as a password when -m is given; the default is des-cbc-crc.

The -M mkeyname option specifies the principal name for the master key in the database (usually K/M in the KDC’s realm).

The -m option specifies that the master database password should be fetched from the keyboard rather than from a stash file.

The -n option specifies that the KDC does not put itself in the background and does not disassociate itself from the terminal. In normal operation, you should always allow the KDC to place itself in the background.

The -P pid_file option tells the KDC to write its PID into pid_file after it starts up. This can be used to identify whether the KDC is still running and to allow init scripts to stop the correct process.

The -p portnum option specifies the default UDP port numbers which the KDC should listen on for Kerberos version 5 requests, as a comma-separated list. This value overrides the UDP port numbers specified in the [kdcdefaults] section of kdc.conf, but may be overridden by realm-specific values. If no value is given from any source, the default ports are 88 and 750.

The -w numworkers option tells the KDC to fork numworkers processes to listen to the KDC ports and process requests in parallel. The top level KDC process (whose pid is recorded in the pid file if the -P option is also given) acts as a supervisor. The supervisor will relay SIGHUP signals to the worker subprocesses, and will terminate the worker subprocess if the it is itself terminated or if any other worker process exits.


On operating systems which do not have pktinfo support, using worker processes will prevent the KDC from listening for UDP packets on network interfaces created after the KDC starts.

The -x db_args option specifies database-specific arguments. Options supported for the LDAP database module are:

-x nconns=<number_of_connections>
Specifies the number of connections to be maintained per LDAP server.
-x host=<ldapuri>
Specifies the LDAP server to connect to by URI.
-x binddn=<binddn>
Specifies the DN of the object used by the KDC server to bind to the LDAP server. This object should have read and write privileges to the realm container, the principal container, and the subtree that is referenced by the realm.
-x bindpwd=<bind_password>
Specifies the password for the above mentioned binddn. Using this option may expose the password to other users on the system via the process list; to avoid this, instead stash the password using the stashsrvpw command of kdb5_ldap_util.
-x debug=level
sets the OpenLDAP client library debug level. level is an integer to be interpreted by the library. Debugging messages are printed to standard error, so this option must be used with the -n option to be useful. New in release 1.12.

The -T offset option specifies a time offset, in seconds, which the KDC will operate under. It is intended only for testing purposes.


The KDC may service requests for multiple realms (maximum 32 realms). The realms are listed on the command line. Per-realm options that can be specified on the command line pertain for each realm that follows it and are superseded by subsequent definitions of the same option.

For example:

krb5kdc -p 2001 -r REALM1 -p 2002 -r REALM2 -r REALM3

specifies that the KDC listen on port 2001 for REALM1 and on port 2002 for REALM2 and REALM3. Additionally, per-realm parameters may be specified in the kdc.conf file. The location of this file may be specified by the KRB5_KDC_PROFILE environment variable. Per-realm parameters specified in this file take precedence over options specified on the command line. See the kdc.conf description for further details.


krb5kdc uses the following environment variables: