Why you shouldn't chmod 500 /bin/login

[John Quarterman]

Quoting:

	The big win of the builtin shell "login" command is that it logs me out
	and lets you log in without hanging up the modem line.  If you chmod
	500 /bin/login, then the line will drop when exec("/bin/login") fails.
	Inconvenient.

	  -- Andrew Klossner   (decvax!tektronix!orca!andrew)       [UUCP]
	                       (orca!andrew.tektronix at csnet-relay)  [ARPA]

Of course the chmod will cause that behavior.  It is a very minor
inconvenience.  Another person uses my terminal and modem daily, and
neither of us are bothered by this:  most modems these days can re-dial
a number on a couple of keystrokes.  (I don't have much sympathy for
people who only have 300 baud, either.)

If you have a port selector which requires some sort of complicated
negotiation, it might actually be enough of a hassle to allow recursive
logins.  Of course, you've then got to worry about things like mail
return addresses, whether the various accounting commands and last(1)
will work correctly, and the convenient availability of an executable
/bin/login for use by crackers.

We could argue about this endlessly.  If you consider "inconvenient"
alone to be the telling argument, I will not agree with you.  How about
we all go on to something else?
-- 
John Quarterman, CS Dept., University of Texas, Austin, Texas 78712 USA
jsq at ut-sally.ARPA, jsq at ut-sally.UUCP, {ihnp4,seismo,ctvax}!ut-sally!jsq