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Berkeley r-commands

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The Berkeley r-commands are a suite of computer programs designed to enable users of one Unix system to log in or issue commands to another Unix computer via TCP/IP computer network.[1] The r-commands were developed in 1982 by the Computer Systems Research Group at the University of California, Berkeley, based on an early implementation of TCP/IP (the protocol stack of the Internet).[2]

The CSRG incorporated the r-commands into their Unix operating system, the Berkeley Software Distribution (BSD). The r-commands premiered in BSD v4.1.[2] Among the programs in the suite are: rcp (remote copy), rexec (remote execution), rlogin (remote login), rsh (remote shell), rstat, ruptime, and rwho (remote who).[2][3]

The r-commands were a significant innovation, and became de facto standards for Unix operating systems.[4][5]

rlogin

Overview
Service Port Transport Refs
Client Daemon
rcp 514 TCP
rexec 512 TCP [6]
rlogin rlogind 513 TCP [7]
rsh rshd 514 TCP
rstat rstatd UDP
ruptime rwhod 513 UDP [8]
rwho [7][8]

rlogin enables a user to log in on another server via computer network, using TCP network port 513.

rlogin is also the name of the application layer protocol used by the software, part of the TCP/IP protocol suite. Authenticated users can act as if they were physically present at the computer. RFC 1282, in which it was defined, states: "The rlogin facility provides a remote-echoed, locally flow-controlled virtual terminal with proper flushing of output." rlogin communicates with a daemon, rlogind, on the remote host. rlogin is similar to the Telnet command, but is not as customizable and is able to connect only to Unix-like hosts.

rcp, rexec, rsh, and rwho

Further information: Remote Shell

The original Berkeley package that provides rlogin also features rcp (remote-copy, allowing files to be copied over the network) and rsh (remote-shell, allowing commands to be run on a remote machine without the user logging into it). These share the hosts.equiv and .rhosts access-control scheme (although they connect to a different daemon, rshd), and as such suffer from the same security exposures. The Secure Shell suite contains suitable replacements for both: scp replaces rcp, and ssh replaces both rlogin and rsh.

Like rsh, rexec enables the user to run shell commands on a remote computer. However, unlike the rsh server, the rexec server (rexecd) authenticates users by reading the username and password (unencrypted) from the socket.[9] rexec uses TCP port 512.

With rwho, a user can display a list of users who are logged into a remote, multi-user computer.

See also

Notes

  1. ^ Horwitz, Jeff (2003) [2002]. "Using the Berkeley r-commands Without a Password". Unix System Management: Primer Plus. Sams Publishing. p. 339. ISBN 978-0-672-32372-0. Retrieved 2018-03-04 – via Google Books.
  2. ^ a b c McKusick, Marshall Kirk (1999). "Twenty Years of Berkeley Unix: From AT&T-Owned to Freely Redistributable". Open Sources: Voices from the Open Source Revolution. O'Reilly & Associates. Section: "4.2BSD". ISBN 978-1-56592-582-3. Retrieved 2018-03-03.
  3. ^ Pyles, James; Carrell, Jeffrey L.; Tittel, Ed (2017). "Which IP Services Are Most Vulnerable?". Guide to TCP/IP: IPv6 and IPv4 (5th ed.). Cengage Learning. p. 659. ISBN 978-1-305-94695-8 – via Google Books.
  4. ^ Casad (2008), p. 346
  5. ^ Negus, Christopher. "About "r" Commands". Red Hat Fedora Linux 2 Bible. Wiley. ISBN 0-7645-5745-9. OCLC 441918216. Retrieved 2018-03-04.
  6. ^ "REXEC command—Execute a command on the remote host and receive the results on your local host". z/OS Communications Server: IP User's Guide and Commands. 2013 [1990]. Retrieved 2018-03-04.
  7. ^ a b "More on Ports". FreeBSD Network Administrators Guide. Retrieved 2018-03-04.
  8. ^ a b Casad (2008), pp. 350–51
  9. ^ "rexecd(8)". manpagez.com. Retrieved 2018-03-03.

References

  • This article is based on material taken from the Free On-line Dictionary of Computing prior to 1 November 2008 and incorporated under the "relicensing" terms of the GFDL, version 1.3 or later.
  • Casad, Joe (2008). "Berkeley Remote Utilities". Sams Teach Yourself TCP/IP in 24 Hours. Pearson Education. ISBN 978-0-13-271513-3 – via Google Books.

Further reading


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