rshserver

rshserver refers to the daemon component that implements the remote shell (RSH) protocol, enabling the execution of commands on a remote host from a local client. It is commonly implemented by a program named rshd and has historically been part of BSD Unix and other UNIX-like environments. In typical deployments, rshd runs under a supervisor such as inetd, xinetd, or systemd and listens for incoming connections on the RSH service port. Upon receiving a request, it authenticates the client and, if permitted, executes the specified command with the appropriate user privileges on the target system.

Authentication for rsh is based on trust relationships rather than passwords. Access control is usually defined using host-based files such as .rhosts in the user’s home directory or system-wide equivalents like hosts.equiv. While this design can simplify automated administration, it introduces significant security risks because access is granted based on host identity and user matching, which can be spoofed or compromised if not carefully managed. As a result, rsh is widely regarded as insecure in modern networks.

Security and administration considerations have led many systems to disable rsh services by default and to recommend secure alternatives. When used, administrators may supplement access controls with TCP wrappers or equivalent mechanisms, though these do not address the protocol’s fundamental vulnerabilities. The contemporary recommended replacement is SSH, which provides encrypted communication, stronger authentication, and safer remote command execution practices.

See also: rsh, rsh client, rlogin, SSH.