The hosts.equiv file 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][username]
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 expicitly deny access
to a host by preceding the hostname 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.
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"!
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.
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 promiscuous is added to the auth
component line in your PAM file for the particular service (e.g.