man-pages/man5/hosts.equiv.5.html
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<H1>HOSTS.EQUIV</H1>
Section: Linux Programmer's Manual (5)<BR>Updated: 2015-07-23<BR><A HREF="#index">Index</A>
<A HREF="/cgi-bin/man/man2html">Return to Main Contents</A><HR>
<A NAME="lbAB">&nbsp;</A>
<H2>NAME</H2>
hosts.equiv - list of hosts and users that are granted &quot;trusted&quot;
<B>r</B>
command access to your system
<A NAME="lbAC">&nbsp;</A>
<H2>DESCRIPTION</H2>
The file
<I>/etc/hosts.equiv</I>
allows or denies hosts and users to use
the <B>r</B>-commands (e.g.,
<B>rlogin</B>,
<B>rsh</B>,
or
<B>rcp</B>)
without
supplying a password.
<P>
The file uses the following format:
<DL COMPACT>
<DT id="1"><I>+|[-]hostname|+@netgroup|-@netgroup</I> <I>[+|[-]username|+@netgroup|-@netgroup]</I><DD>
</DL>
<P>
The
<I>hostname</I>
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
<I>hostname</I>
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
<I>hostname</I>
by a minus (-) sign.
Users from that host must always supply additional credentials,
including possibly a password. For security reasons you should always
use the FQDN of the hostname and not the short hostname.
<P>
The
<I>username</I>
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
<I>username</I>
may
be (optionally) preceded by a plus (+) sign.
You can also explicitly
deny access to a specific user by preceding the
<I>username</I>
with
a minus (-) sign.
This says that the user is not trusted no matter
what other entries for that host exist.
<P>
Netgroups can be specified by preceding the netgroup by an @ sign.
<P>
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 &quot;any host&quot;!
<A NAME="lbAD">&nbsp;</A>
<H2>FILES</H2>
<I>/etc/hosts.equiv</I>
<A NAME="lbAE">&nbsp;</A>
<H2>NOTES</H2>
Some systems will honor the contents of this file only 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.
<P>
Modern systems use the Pluggable Authentication Modules library (PAM).
With PAM a standalone plus sign is considered a wildcard
character which means &quot;any host&quot; only when the word
<I>promiscuous</I>
is added to the auth component line in your PAM file for
the particular service
(e.g., <B>rlogin</B>).
<A NAME="lbAF">&nbsp;</A>
<H2>EXAMPLE</H2>
Below are some example
<I>/etc/host.equiv</I>
or
<I>~/.rhosts</I>
files.
<P>
Allow any user to log in from any host:
<P>
<BR>&nbsp;&nbsp;&nbsp;&nbsp;+
<P>
Allow any user from
<I>host</I>
with a matching local account to log in:
<P>
<BR>&nbsp;&nbsp;&nbsp;&nbsp;host
<P>
Note: the use of
<I>+host</I>
is never a valid syntax,
including attempting to specify that any user from the host is allowed.
<P>
Allow any user from
<I>host</I>
to log in:
<P>
<BR>&nbsp;&nbsp;&nbsp;&nbsp;host&nbsp;+
<P>
Note: this is distinct from the previous example
since it does not require a matching local account.
<P>
Allow
<I>user</I>
from
<I>host</I>
to log in as any non-root user:
<P>
<BR>&nbsp;&nbsp;&nbsp;&nbsp;host&nbsp;user
<P>
Allow all users with matching local accounts from
<I>host</I>
to log in except for
<I>baduser</I>:
<P>
<BR>&nbsp;&nbsp;&nbsp;&nbsp;host&nbsp;-baduser
<BR>&nbsp;&nbsp;&nbsp;&nbsp;host
<P>
Deny all users from
<I>host</I>:
<P>
<BR>&nbsp;&nbsp;&nbsp;&nbsp;-host
<P>
Note: the use of
<I>-host&nbsp;-user</I>
is never a valid syntax,
including attempting to specify that a particular user from the host
is not trusted.
<P>
Allow all users with matching local accounts on all hosts in a
<I>netgroup</I>:
<P>
<BR>&nbsp;&nbsp;&nbsp;&nbsp;+@netgroup
<P>
Disallow all users on all hosts in a
<I>netgroup</I>:
<P>
<BR>&nbsp;&nbsp;&nbsp;&nbsp;-@netgroup
<P>
Allow all users in a
<I>netgroup</I>
to log in from
<I>host</I>
as any non-root user:
<P>
<BR>&nbsp;&nbsp;&nbsp;&nbsp;host&nbsp;+@netgroup
<P>
Allow all users with matching local accounts on all hosts in a
<I>netgroup</I>
except
<I>baduser</I>:
<P>
<BR>&nbsp;&nbsp;&nbsp;&nbsp;+@netgroup&nbsp;-baduser
<BR>&nbsp;&nbsp;&nbsp;&nbsp;+@netgroup
<P>
Note: the deny statements must always precede the allow statements because
the file is processed sequentially until the first matching rule is found.
<A NAME="lbAG">&nbsp;</A>
<H2>SEE ALSO</H2>
<B><A HREF="/cgi-bin/man/man2html?5+rhosts">rhosts</A></B>(5),
<B><A HREF="/cgi-bin/man/man2html?8+rlogind">rlogind</A></B>(8),
<B><A HREF="/cgi-bin/man/man2html?8+rshd">rshd</A></B>(8)
<A NAME="lbAH">&nbsp;</A>
<H2>COLOPHON</H2>
This page is part of release 5.05 of the Linux
<I>man-pages</I>
project.
A description of the project,
information about reporting bugs,
and the latest version of this page,
can be found at
<A HREF="https://www.kernel.org/doc/man-pages/.">https://www.kernel.org/doc/man-pages/.</A>
<P>
<HR>
<A NAME="index">&nbsp;</A><H2>Index</H2>
<DL>
<DT id="2"><A HREF="#lbAB">NAME</A><DD>
<DT id="3"><A HREF="#lbAC">DESCRIPTION</A><DD>
<DT id="4"><A HREF="#lbAD">FILES</A><DD>
<DT id="5"><A HREF="#lbAE">NOTES</A><DD>
<DT id="6"><A HREF="#lbAF">EXAMPLE</A><DD>
<DT id="7"><A HREF="#lbAG">SEE ALSO</A><DD>
<DT id="8"><A HREF="#lbAH">COLOPHON</A><DD>
</DL>
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