Telnet & rlogin

Derek Martin dmartin at
Mon Feb 14 11:52:38 EST 2000

On Mon, 14 Feb 2000, Udaya Krishna wrote:

> Hi,
> 	Can anyone explain me the difference in detail between telnet
> and rlogin. I am quite confused with both these terms.

Telnet is a little bit insecure and rsh/rlogin is a LOT insecure. Both
will transmit your password in cleartext if you give it one. rlogin gives
you the ability to log in remotely without supplying a password, but this
can easily be spoofed and is a Bad Thing(TM) in general, though on a
secure, trusted network can be acceptable. Problem being that there is no
such thing as a secure, trusted network that's connected to the outside
world in any way.

> 	From what I know, rlogin can be used only on unix and telnet can
> be used on any system. But, how these two programs differ from
> each other ?

The best answer someone could give you here is "read the man pages."  If
you aren't already, you should get in the habit of reading the man pages,
since (except on Sun Solaris pre-2.7 machines -- UGH) the man pages have
the most complete and detailed information about all of the commands on
your system.  There are also implementation-dependent differences for all
commands from operating system to operating system (i.e. Linux's rsh may
have different options from that of Irix's rsh, etc.).  The only way to
find out about these differences is to read the man pages.

All that said, just download ssh and use that instead.  It's much more
secure (or can be -- you can make it fairly insecure if you try hard) and
a lot more featureful/flexible than either telnet or rlogin/rsh.

On a final note, it isn't necessarily true that you can't use rlogin on
non-Unix platforms... it just so happens that most other platforms don't
provide rlogin.  In theory, you could write an rlogin client for any
system that supports TCP/IP networking, though the implementation might be
a little non-standard on some OSes that are not designed to be multi-user
systems (like MS-DOS).

"Quis custodiet ipsos custodes?"    "Who watches the watchmen?" 
-Juvenal, Satires, VI, 347 

Derek D. Martin      |  Senior UNIX Systems/Network Administrator
Arris Interactive    |  A Nortel Company
derekm at  |  dmartin at

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