hosts.equiv(5) - phpMan

HOSTS.EQUIV(5) Linux Programmer's Manual HOSTS.EQUIV(5)

NAME
hosts.equiv - list of hosts and users that are granted "trusted" r command access to your
system

DESCRIPTION
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:

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) with-
out 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 re-
sult in a standalone plus sign. A standalone plus sign is a wildcard character that means
"any host"!

FILES
/etc/hosts.equiv

NOTES
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 stand-
alone 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).

EXAMPLES
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 lo-
cal 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.