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.\" Man page generated from reStructuredText. . .TH "KERBEROS" "7" " " "1.17" "MIT Kerberos" .SH NAME kerberos \- Overview of using Kerberos . .nr rst2man-indent-level 0 . .de1 rstReportMargin \\$1 \\n[an-margin] level \\n[rst2man-indent-level] level margin: \\n[rst2man-indent\\n[rst2man-indent-level]] - \\n[rst2man-indent0] \\n[rst2man-indent1] \\n[rst2man-indent2] .. .de1 INDENT .\" .rstReportMargin pre: . RS \\$1 . nr rst2man-indent\\n[rst2man-indent-level] \\n[an-margin] . nr rst2man-indent-level +1 .\" .rstReportMargin post: .. .de UNINDENT . RE .\" indent \\n[an-margin] .\" old: \\n[rst2man-indent\\n[rst2man-indent-level]] .nr rst2man-indent-level -1 .\" new: \\n[rst2man-indent\\n[rst2man-indent-level]] .in \\n[rst2man-indent\\n[rst2man-indent-level]]u .. .SH DESCRIPTION .sp The Kerberos system authenticates individual users in a network environment. After authenticating yourself to Kerberos, you can use Kerberos\-enabled programs without having to present passwords or certificates to those programs. .sp If you receive the following response from kinit(1): .sp kinit: Client not found in Kerberos database while getting initial credentials .sp you haven\(aqt been registered as a Kerberos user. See your system administrator. .sp A Kerberos name usually contains three parts. The first is the \fBprimary\fP, which is usually a user\(aqs or service\(aqs name. The second is the \fBinstance\fP, which in the case of a user is usually null. Some users may have privileged instances, however, such as \fBroot\fP or \fBadmin\fP\&. 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 ssh service running on the machine ABC (\fI\%ssh/ABC@REALM\fP), which is different from the ssh service running on the machine XYZ (\fI\%ssh/XYZ@REALM\fP). The third part of a Kerberos name is the \fBrealm\fP\&. The realm corresponds to the Kerberos service providing authentication for the principal. Realms are conventionally all\-uppercase, and often match the end of hostnames in the realm (for instance, host01.example.com might be in realm EXAMPLE.COM). .sp 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: .INDENT 0.0 .INDENT 3.5 .sp .nf .ft C david jennifer/admin joeuser@BLEEP.COM cbrown/root@FUBAR.ORG .ft P .fi .UNINDENT .UNINDENT .sp When you authenticate yourself with Kerberos you get an initial Kerberos \fBticket\fP\&. (A Kerberos ticket is an encrypted protocol message that provides authentication.) Kerberos uses this ticket for network utilities such as ssh. The ticket transactions are done transparently, so you don\(aqt have to worry about their management. .sp Note, however, that tickets expire. Administrators may configure more privileged tickets, such as those with service or instance of \fBroot\fP or \fBadmin\fP, to expire in a few minutes, while tickets that carry more ordinary privileges may be good for several hours or a day. If your login session extends beyond the time limit, you will have to re\-authenticate yourself to Kerberos to get new tickets using the kinit(1) command. .sp Some tickets are \fBrenewable\fP beyond their initial lifetime. This means that \fBkinit \-R\fP can extend their lifetime without requiring you to re\-authenticate. .sp If you wish to delete your local tickets, use the kdestroy(1) command. .sp Kerberos tickets can be forwarded. In order to forward tickets, you must request \fBforwardable\fP tickets when you kinit. Once you have forwardable tickets, most Kerberos programs have a command line option to forward them to the remote host. This can be useful for, e.g., running kinit on your local machine and then sshing into another to do work. Note that this should not be done on untrusted machines since they will then have your tickets. .SH ENVIRONMENT VARIABLES .sp Several environment variables affect the operation of Kerberos\-enabled programs. These include: .INDENT 0.0 .TP \fBKRB5CCNAME\fP Default name for the credentials cache file, in the form \fITYPE\fP:\fIresidual\fP\&. The type of the default cache may determine the availability of a cache collection. \fBFILE\fP is not a collection type; \fBKEYRING\fP, \fBDIR\fP, and \fBKCM\fP are. .sp If not set, the value of \fBdefault_ccache_name\fP from configuration files (see \fBKRB5_CONFIG\fP) will be used. If that is also not set, the default \fItype\fP is \fBFILE\fP, and the \fIresidual\fP is the path /tmp/krb5cc_uid, where \fIuid\fP is the decimal user ID of the user. .TP \fBKRB5_KTNAME\fP Specifies the location of the default keytab file, in the form \fITYPE\fP:\fIresidual\fP\&. If no \fItype\fP is present, the \fBFILE\fP type is assumed and \fIresidual\fP is the pathname of the keytab file. If unset, \fBFILE:/etc/krb5.keytab\fP will be used. .TP \fBKRB5_CONFIG\fP Specifies the location of the Kerberos configuration file. The default is \fB/etc\fP\fB/krb5.conf\fP\&. Multiple filenames can be specified, separated by a colon; all files which are present will be read. .TP \fBKRB5_KDC_PROFILE\fP Specifies the location of the KDC configuration file, which contains additional configuration directives for the Key Distribution Center daemon and associated programs. The default is \fB/opt/alt/krb5/usr/var\fP\fB/krb5kdc\fP\fB/kdc.conf\fP\&. .TP \fBKRB5RCACHETYPE\fP Specifies the default type of replay cache to use for servers. Valid types include \fBdfl\fP for the normal file type and \fBnone\fP for no replay cache. The default is \fBdfl\fP\&. .TP \fBKRB5RCACHEDIR\fP Specifies the default directory for replay caches used by servers. The default is the value of the \fBTMPDIR\fP environment variable, or \fB/var/tmp\fP if \fBTMPDIR\fP is not set. .TP \fBKRB5_TRACE\fP Specifies a filename to write trace log output to. Trace logs can help illuminate decisions made internally by the Kerberos libraries. For example, \fBenv KRB5_TRACE=/dev/stderr kinit\fP would send tracing information for kinit(1) to \fB/dev/stderr\fP\&. The default is not to write trace log output anywhere. .TP \fBKRB5_CLIENT_KTNAME\fP Default client keytab file name. If unset, \fBFILE:/opt/alt/krb5/usr/var/krb5/user/%{euid}/client.keytab\fP will be used). .TP \fBKPROP_PORT\fP kprop(8) port to use. Defaults to 754. .UNINDENT .sp Most environment variables are disabled for certain programs, such as login system programs and setuid programs, which are designed to be secure when run within an untrusted process environment. .SH SEE ALSO .sp kdestroy(1), kinit(1), klist(1), kswitch(1), kpasswd(1), ksu(1), krb5.conf(5), kdc.conf(5), kadmin(1), kadmind(8), kdb5_util(8), krb5kdc(8) .SH BUGS .SH AUTHORS .nf Steve Miller, MIT Project Athena/Digital Equipment Corporation Clifford Neuman, MIT Project Athena Greg Hudson, MIT Kerberos Consortium Robbie Harwood, Red Hat, Inc. .fi .sp .SH HISTORY .sp The MIT Kerberos 5 implementation was developed at MIT, with contributions from many outside parties. It is currently maintained by the MIT Kerberos Consortium. .SH RESTRICTIONS .sp Copyright 1985, 1986, 1989\-1996, 2002, 2011, 2018 Masachusetts Institute of Technology .SH AUTHOR MIT .SH COPYRIGHT 1985-2019, MIT .\" Generated by docutils manpage writer. .