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NAME | DESCRIPTION | FILES | NOTES | EXAMPLES | SEE ALSO | COLOPHON |
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hosts.equiv(5) File Formats Manual hosts.equiv(5)
hosts.equiv - list of hosts and users that are granted "trusted" r
command access to your system
The file /etc/hosts.equiv allows or denies hosts and users to use
the r-commands (e.g., rlogin, rsh, or rcp) without supplying a
password.
The file uses the following format:
+|[-]hostname|+@netgroup|-@netgroup
[+|[-]username|+@netgroup|-@netgroup]
The hostname 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 hostname 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 hostname 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.
The username 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 username
may be (optionally) preceded by a plus (+) sign. You can also
explicitly deny access to a specific user by preceding the
username with a minus (-) sign. This says that the user is not
trusted no matter what other entries for that host exist.
Netgroups can be specified by preceding the netgroup by an @ sign.
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"!
/etc/hosts.equiv
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.
Modern systems use the Pluggable Authentication Modules library
(PAM). With PAM a standalone plus sign is considered a wildcard
character which means "any host" only when the word promiscuous is
added to the auth component line in your PAM file for the
particular service (e.g., rlogin).
Below are some example /etc/host.equiv or ~/.rhosts files.
Allow any user to log in from any host:
+
Allow any user from host with a matching local account to log in:
host
Note: the use of +host is never a valid syntax, including
attempting to specify that any user from the host is allowed.
Allow any user from host to log in:
host +
Note: this is distinct from the previous example since it does not
require a matching local account.
Allow user from host to log in as any non-root user:
host user
Allow all users with matching local accounts from host to log in
except for baduser:
host -baduser
host
Deny all users from host:
-host
Note: the use of -host -user is never a valid syntax, including
attempting to specify that a particular user from the host is not
trusted.
Allow all users with matching local accounts on all hosts in a
netgroup:
+@netgroup
Disallow all users on all hosts in a netgroup:
-@netgroup
Allow all users in a netgroup to log in from host as any non-root
user:
host +@netgroup
Allow all users with matching local accounts on all hosts in a
netgroup except baduser:
+@netgroup -baduser
+@netgroup
Note: the deny statements must always precede the allow statements
because the file is processed sequentially until the first
matching rule is found.
rhosts(5), rlogind(8), rshd(8)
This page is part of the man-pages (Linux kernel and C library
user-space interface documentation) project. Information about
the project can be found at
⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report
for this manual page, see
⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
This page was obtained from the tarball man-pages-6.15.tar.gz
fetched from
⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on
2025-08-11. If you discover any rendering problems in this HTML
version of the page, or you believe there is a better or more up-
to-date source for the page, or you have corrections or
improvements to the information in this COLOPHON (which is not
part of the original manual page), send a mail to
[email protected]
Linux man-pages 6.15 2025-05-17 hosts.equiv(5)
Pages that refer to this page: pam_rhosts(8)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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