Berkeley r-commands: Difference between revisions

Revision as of 16:23, 4 March 2018

Revision as of 20:15, 6 March 2018

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rlogin is also the name of the [[application layer]] [[Communications protocol|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 (computer software)|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|Remote Shell}}

The original Berkeley package that provides rlogin also features rcp (remote-copy, allowing files to be copied over the network) and [[Remote Shell|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.<ref>{{cite web |url=http://www.manpagez.com/man/8/rexecd/ |title=rexecd(8) |website=manpagez.com |access-date=2018-03-03}}</ref> rexec uses TCP port 512.

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

==rcp==

rcp can copy a file or directory from the local system to a remote system, from a remote system to the local system, or from one remote system to another.<ref name="Farrell">{{cite web |url=https://earthsci.stanford.edu/computing/unix/netcommands/rcp.php |title=rcp |last=Farrell |first=Phillip |date=3 August 2004 |website=earthsci.stanford.edu |publisher=Stanford University School of Earth, Energy & Environmental Sciences |access-date=2018-03-06}}</ref> The command line [[Parameter (computer programming)|arguments]] of cp and rcp are similar, but in rcp remote files are prefixed with the name of the remote system:

cp file.txt subdomain.___domain:~/home/foo/file.txt

As with the Unix copy command [[cp (Unix)|cp]], rcp overwrites an existing file of the same name in the target; unlike cp, it provides no mechanism for warning the user before overwriting the target file.<ref name="Farrell"/> Like rsh, rcp uses TCP port 514.<ref>{{cite web |url=http://sourcedaddy.com/networking/rlogin-rsh-and-rcp.html |title=Rlogin, RSH, and RCP |website=SourceDaddy |access-date=2018-02-18}}</ref>

== See also ==