man-pages/man5/hosts.equiv.5

.\" Copyright (c) 1995 Peter Tobias <tobias@et-inf.fho-emden.de>
.\" This file may be distributed under the GNU General Public License.
.TH HOSTS.EQUIV 5 2003-08-24 "Linux" "Linux Programmer's Manual"
.SH NAME
/etc/hosts.equiv \- list of hosts and users that are granted "trusted"
\fBr\fP command access to your system
.SH DESCRIPTION
The \fBhosts.equiv\fP file allows or denies hosts and users to use
the \fBr\fP-commands (e.g., \fBrlogin\fP, \fBrsh\fP or \fBrcp\fP) without
supplying a password.
.PP
The file uses the following format:
.TP
\fI[ + | \- ]\fP \fI[hostname]\fP \fI[username]\fP
.PP
The \fIhostname\fP is the name of a host which is logically equivalent
to the local host.
Users logged into that host are allowed to access
like-named user accounts on the local host without supplying a password.
The \fIhostname\fP may be (optionally) preceded by a plus (+) sign.
If the plus sign is used alone it allows any host to access your system.
You can explicitly deny access to a host by preceding the \fIhostname\fP
by a minus (\-) sign.
Users from that host must always supply a password.
For security reasons you should always use the FQDN of the hostname and
not the short hostname.
.PP
The \fIusername\fP entry grants a specific user access to all user
accounts (except root) without supplying a password.
That means the
user is NOT restricted to like-named accounts.
The \fIusername\fP may
be (optionally) preceded by a plus (+) sign.
You can also explicitly
deny access to a specific user by preceding the \fIusername\fP with
a minus (\-) sign.
This says that the user is not trusted no matter
what other entries for that host exist.
.PP
Netgroups can be specified by preceding the netgroup by an @ sign.
.PP
Be extremely careful when using the plus (+) sign.
A simple typographical
error could result in a standalone plus sign.
A standalone plus sign is
a wildcard character that means "any host"!
.SH FILES
.I /etc/hosts.equiv
.SH NOTES
Some systems will only honor the contents of this file when it has owner
root and no write permission for anybody else.
Some exceptionally
paranoid systems even require that there be no other hard links to the file.
.PP
Modern systems use the Pluggable Authentication Modules library (PAM).
With PAM a standalone plus sign is only considered a wildcard
character which means "any host" when the word
.I promiscuous
is added to the auth component line in your PAM file for
the particular service
.RB "(e.g., " rlogin ).
.SH "SEE ALSO"
.BR rhosts (5),
.BR rlogind (8),
.BR rshd (8)