The Kerberos system authenticates individual users in a network
environment. After authenticating yourself to Kerberos, you can use
network 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:
kinit(v5): Client not found in Kerberos database while getting initial
credentials
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:
david
jennifer/admin
joeuser@BLEEP.COM
cbrown/root@FUBAR.ORG
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 transparently, 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-authenticate yourself.
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 forwardable 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 .
