RHOSTS(5) BSD File Formats Manual RHOSTS(5)NAME
rhosts -- allow rlogin, rsh and rcp connections to the local machine without a password.
The .rhosts file can allow specific remote users and/or hosts to execute commands on the local machine. The file uses the following format:
host [user | @group]
Such an entry grants password-free access for the user with the login name user from host. If no user is specified, the user must have the
same login name on the remote host and the local host. For security reasons you should always use the FQDN of the hostname and not the short
hostname. Netgroups can be specified by preceeding the group by an @ sign.
The .rhosts file must be owned by the user or root, and writable only by the owner.
SEE ALSO rsh(1), rlogin(1), rcp(1).
September 9, 2019
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HOSTS.EQUIV(5) BSD File Formats Manual HOSTS.EQUIV(5)NAME
hosts.equiv, .rhosts -- trusted remote hosts and host-user pairs
The hosts.equiv and .rhosts files list hosts and users which are ``trusted'' by the local host when a connection is made via rlogind(8),
rshd(8), or any other server that uses ruserok(3). This mechanism bypasses password checks, and is required for access via rsh(1).
Each line of these files has the format:
The hostname may be specified as a host name (typically a fully qualified host name in a DNS environment) or address, ``+@netgroup'' (from
which only the host names are checked), or a ``+'' wildcard (allow all hosts).
The username, if specified, may be given as a user name on the remote host, ``+@netgroup'' (from which only the user names are checked), or a
``+'' wildcard (allow all remote users).
If a username is specified, only that user from the specified host may login to the local machine. If a username is not specified, any user
may login with the same user name.
A common usage: users on somehost may login to the local host as the same user name.
The user username on somehost may login to the local host. If specified in /etc/hosts.equiv, the user may login with only the same
The user username may login to the local host from any machine listed in the netgroup anetgroup.
Two severe security hazards. In the first case, allows a user on any machine to login to the local host as the same user name. In the
second case, allows any user on any machine to login to the local host (as any user, if in /etc/hosts.equiv).
The username checks provided by this mechanism are not secure, as the remote user name is received by the server unchecked for validity.
Therefore this mechanism should only be used in an environment where all hosts are completely trusted.
A numeric host address instead of a host name can help security considerations somewhat; the address is then used directly by iruserok(3).
When a username (or netgroup, or +) is specified in /etc/hosts.equiv, that user (or group of users, or all users, respectively) may login to
the local host as any local user. Usernames in /etc/hosts.equiv should therefore be used with extreme caution, or not at all.
A .rhosts file must be owned by the user whose home directory it resides in, and must be writable only by that user.
Logins as root only check root's .rhosts file; the /etc/hosts.equiv file is not checked for security. Access permitted through root's
.rhosts file is typically only for rsh(1), as root must still login on the console for an interactive login such as rlogin(1).
/etc/hosts.equiv Global trusted host-user pairs list
~/.rhosts Per-user trusted host-user pairs list
SEE ALSO rcp(1), rlogin(1), rsh(1), rcmd(3), ruserok(3), netgroup(5)HISTORY
The .rhosts file format appeared in 4.2BSD.
The ruserok(3) implementation currently skips negative entries (preceded with a ``-'' sign) and does not treat them as ``short-circuit'' neg-
BSD November 26, 1997 BSD