KERBEROS(1) General Commands Manual KERBEROS(1)
kerberos - introduction to the Kerberos system
The Kerberos system authenticates individual users in a network environment. After authenticating yourself to Kerberos, you can use net-
work utilities such as rlogin, rcp, and rsh without having to present passwords to remote hosts and without having to bother with .rhosts
files. Note that these utilities will work without passwords only if the remote machines you deal with support the Kerberos system.
If you enter your username and kinit responds with this message:
Principal unknown (kerberos)
you haven't been registered as a Kerberos user. See your system administrator.
A Kerberos name usually contains three parts. The first is the primary, which is usually a user's or service's name. The second is the
instance, which in the case of a user is usually null. Some users may have privileged instances, however, such as ``root'' or ``admin''.
In the case of a service, the instance is the fully qualified name of the machine on which it runs; i.e. there can be an rlogin service
running on the machine ABC, which is different from the rlogin service running on the machine XYZ. The third part of a Kerberos name is
the realm. The realm corresponds to the Kerberos service providing authentication for the principal.
When writing a Kerberos name, the principal name is separated from the instance (if not null) by a slash, and the realm (if not the local
realm) follows, preceded by an ``@'' sign. The following are examples of valid Kerberos names:
When you authenticate yourself with Kerberos you get an initial Kerberos ticket. (A Kerberos ticket is an encrypted protocol message that
provides authentication.) Kerberos uses this ticket for network utilities such as rlogin and rcp. The ticket transactions are done trans-
parently, so you don't have to worry about their management.
Note, however, that tickets expire. Privileged tickets, such as those with the instance ``root'', expire in a few minutes, while tickets
that carry more ordinary privileges may be good for several hours or a day, depending on the installation's policy. If your login session
extends beyond the time limit, you will have to re-authenticate yourself to Kerberos to get new tickets. Use the kinit command to re-
If you use the kinit command to get your tickets, make sure you use the kdestroy command to destroy your tickets before you end your login
session. You should put the kdestroy command in your .logout file so that your tickets will be destroyed automatically when you logout.
For more information about the kinit and kdestroy commands, see the kinit(1) and kdestroy(1) manual pages.
Kerberos tickets can be forwarded. In order to forward tickets, you must request forwardable tickets when you kinit. Once you have for-
wardable tickets, most Kerberos programs have a command line option to forward them to the remote host.
Currently, Kerberos support is available for the following network services: rlogin, rsh, rcp, telnet, ftp, krdist (a Kerberized version of
rdist), ksu (a Kerberized version of su), login, and Xdm.
kdestroy(1), kinit(1), klist(1), kpasswd(1), rsh(1), rcp(1), rlogin(1), telnet(1), ftp(1), krdist(1), ksu(1), sclient(1), xdm(1),
des_crypt(3), hash(3), krb5strings(3), krb5.conf(5), kdc.conf(5), kadmin(8), kadmind(8), kdb5_util(8), telnetd(8), ftpd(8), rdistd(8),
sserver(8), klogind(8c), kshd(8c), login(8c)
Steve Miller, MIT Project Athena/Digital Equipment Corporation
Clifford Neuman, MIT Project Athena
Kerberos was developed at MIT. OpenVision rewrote and donated the administration server, which is used in the current version of Kerberos
Copyright 1985,1986,1989-1996 Massachusetts Institute of Technology