Unix Tip: KEEPING MORE USERS OUT

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UNIX GURU UNIVERSE
UNIX HOT TIP

Unix Tip 2197 - January 6, 2006

http://www.ugu.com/sui/ugu/show?tip.today

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KEEPING MORE USERS OUT

Here's an alternate approach to tip 1807, regarding keeping users from logging in during maintenance (or whatever).

Create a file called "nologin" that contains the text of a message to display to denied login attempts. The file location depends on the UNIX variant. BSD-derivatives (including Solaris) seem to favor /etc. Linux prefers /var/run.
Make the file world-readable.

With that file in place, anyone (except root) attempting to log in will be shown the contents of the file, and then dropped. Some variants will (I think) await a keystroke, to be sure the message is seen - others just flash it by.
I don't know if that timing is tuneable.

This is referenced in the man page for the login command.

Several years ago, in an environment where I had to deal with this a lot, I worked up a script (cryptically named "logins") that would either query the state of login acess, or allow me to toggle it on or off quickly. It's not elegant, but it did the job. If anyone is interested, I'd be happy to send it.
8-)

This tip is supported by: swezwho@yahoo.com

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