Remote Shell
Encyclopedia
The remote shell is a command line computer program
Computer program
A computer program is a sequence of instructions written to perform a specified task with a computer. A computer requires programs to function, typically executing the program's instructions in a central processor. The program has an executable form that the computer can use directly to execute...

 that can execute shell commands as another user
User (computing)
A user is an agent, either a human agent or software agent, who uses a computer or network service. A user often has a user account and is identified by a username , screen name , nickname , or handle, which is derived from the identical Citizen's Band radio term.Users are...

, and on another computer across a computer network
Computer network
A computer network, often simply referred to as a network, is a collection of hardware components and computers interconnected by communication channels that allow sharing of resources and information....

.

The remote system to which rsh connects runs the rshd daemon
Daemon (computer software)
In Unix and other multitasking computer operating systems, a daemon is a computer program that runs as a background process, rather than being under the direct control of an interactive user...

. The rshd daemon typically uses the well-known Transmission Control Protocol
Transmission Control Protocol
The Transmission Control Protocol is one of the core protocols of the Internet Protocol Suite. TCP is one of the two original components of the suite, complementing the Internet Protocol , and therefore the entire suite is commonly referred to as TCP/IP...

 (TCP) port number 514.

History

Rsh originated as part of the BSD Unix
Berkeley Software Distribution
Berkeley Software Distribution is a Unix operating system derivative developed and distributed by the Computer Systems Research Group of the University of California, Berkeley, from 1977 to 1995...

 operating system
Operating system
An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...

, along with rcp
Rcp (Unix)
rcp stands for the Unix 'remote copy' command. It is a command on the Unix operating systems that is used to remotely copy—to copy one or more files from one computer system to another...

, as part of the rlogin
Rlogin
rlogin is a software utility for Unix-like computer operating systems that allows users to log in on another host via a network, communicating via TCP port 513.It was first distributed as part of the 4.2BSD release....

 package on 4.2BSD in 1983. rsh has since been ported to other operating systems.

The rsh command has the same name as another common UNIX utility, the restricted shell
Restricted shell
The restricted shell is a Unix shell that restricts some of the capabilities available to an interactive user session, or to a shell script, running within it. It is intended to provide an additional layer of security, but is insufficient to allow execution of entirely untrusted software...

, which first appeared in PWB/UNIX
PWB/UNIX
The Programmer's Workbench was an early version of the Unix operating system created in the Bell Labs Computer Science Research Group of AT&T....

; in System V Release 4, the restricted shell is often located at /usr/bin/rsh.

Limitations

As described in the rlogin
Rlogin
rlogin is a software utility for Unix-like computer operating systems that allows users to log in on another host via a network, communicating via TCP port 513.It was first distributed as part of the 4.2BSD release....

 article, the rsh protocol is not secure
Computer security
Computer security is a branch of computer technology known as information security as applied to computers and networks. The objective of computer security includes protection of information and property from theft, corruption, or natural disaster, while allowing the information and property to...

 for network use, because it sends unencrypted information
Cryptography
Cryptography is the practice and study of techniques for secure communication in the presence of third parties...

 over the network, among other reasons. Some implementations also authenticate
Authentication
Authentication is the act of confirming the truth of an attribute of a datum or entity...

 by sending unencrypted password
Password
A password is a secret word or string of characters that is used for authentication, to prove identity or gain access to a resource . The password should be kept secret from those not allowed access....

s over the network. rsh has largely been replaced with the secure shell
Secure Shell
Secure Shell is a network protocol for secure data communication, remote shell services or command execution and other secure network services between two networked computers that it connects via a secure channel over an insecure network: a server and a client...

 (ssh) program on untrusted networks like the Internet
Internet
The Internet is a global system of interconnected computer networks that use the standard Internet protocol suite to serve billions of users worldwide...

.

Example

As an example of rsh use, the following executes the command mkdir testdir as user remoteuser on the computer host.example.com running a UNIX-like system:
rsh -l remoteuser host.example.com "mkdir testdir"

After the command has finished rsh terminates. If no command is specified then rsh will log in on the remote system using rlogin
Rlogin
rlogin is a software utility for Unix-like computer operating systems that allows users to log in on another host via a network, communicating via TCP port 513.It was first distributed as part of the 4.2BSD release....

. The network location of the remote computer is looked up using the Domain Name System
Domain name system
The Domain Name System is a hierarchical distributed naming system for computers, services, or any resource connected to the Internet or a private network. It associates various information with domain names assigned to each of the participating entities...

.
The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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