Introduction to the Unix Cluster. Node: telnet and rlogin

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telnet and rlogin

If you are already logged into one machine, and/or you are on an X-terminal and your desired host isn't among the menu of choices, there is the option of using either the command telnet or the command for a Remote Login, rlogin. All of the computers here at the laboratory are connected together via a network, which allows fairly free interchange between systems. For example, suppose our user `karney' was already logged into Suntsu and now wishes to log onto HAX. He could type and see:

        [lyman|3] telnet hax
        Connected to hax.
        Escape character is '^]'.
        Username: karney 
                    VAX/VMS V5.5-2
  *  Warning:  Unauthorized access to this computer system is  *
  *  prohibited.  Violators are subject to criminal and civil  *
  *  penalties.                                                *
Last interactive login on Friday,  9-JUL-1993 11:06

If we had used the command rlogin, the result would have been the same. The only difference between the two commands is that the first is used mostly when dealing with large-scale networks, while rlogin assumes more of a localized cluster of computers and takes advantage of a (presumed to be existing) `~/.rhosts' file on the target computer. This file includes a computer name and username on that computer (i.e. your username on HAX may be different from that on the UNIX machines), allowing that user to log in and bypass the normal login procedures. The nice thing about this system is that you only have to give your password once (when you log onto your X terminal).

A file similar to the `/.rhosts' file is the `.netrc' file, which holds ftp remote login data. See FTP, and man netrc for more information.

On the PPPL UNIX machines, a useful shorthand version of rlogin is to simply type the name of your intended host:

        [lyman|4] suntsu

Again, as in the case with xrsh, the absence of a command after the host name implies a default command. Here the default is rlogin, allowing you to log in to that computer. In addition, this process requires that `/usr/hosts' be in your PATH in `~/.cshrc'. After logging out (same process as with direct login), the prompt returns to that of your original login computer.

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