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NAME | DESCRIPTION | FILES | NOTES | EXAMPLE | SEE ALSO | COLOPHON |
HOSTS.EQUIV(5) Linux Programmer's 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 release 4.12 of the Linux man-pages project. A
description of the project, information about reporting bugs, and the
latest version of this page, can be found at
https://www.kernel.org/doc/man-pages/.
Linux 2015-07-23 HOSTS.EQUIV(5)
Pages that refer to this page: pam_rhosts(8)