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by Guido Socher
About the author:
Guido is a long time Linux fan. Most of the time he develops software or works for LinuxFocus, but from time to time he likes to design hardware parts.
In this article we design a little push button to connect to your server on the serial line. You can use it to shut the machine down when needed.
A real server machine does normally not need any keyboard, monitor or mouse. It needs a good operating system, like Linux, and a network card. External devices like mouse and keyboard disturb only. With Linux running on the machine, remote administration is the best and most convenient solution.
When I buy a computer I always verify that it has an BIOS option to not check for keyboard at startup. All good motherboard manufactures have that option today. Some that still think people run only Windows on their machines require a keyboard at startup but that is a different story and I don't recommend to buy such hardware.
Such a computer without keyboard and monitor is the perfect computer for a firewall, a web-server, a NFS file server, a mail-server, an ADSL gateway computer etc. It does not have to be a powerful machine. An old pentium 100Mhz with enough RAM will easily serve a hundred and more other machines.
Having no keyboard connected is nice and convenient because the server is then just a small box that fits somewhere in the corner or on a shelf in the cellar. Sometimes you would however like to have a button to properly shut it down without logging first in and running the shutdown command. It could be that you are already in the server room and the next workstation is 100 meters away or you have somebody who has physical access to the machine but no root password and that person needs to shutdown the computer before taking away the power supply.
Just powering it off is no good idea because you might loose data and the disk check during start up takes then very long time.
The solution is the small and inexpensive serial device presented in this article.
9 PIN D-SUB MALE at the Computer.
|9 PIN-connector||25 PIN-connector||Name||Dir||Description|
|4||20||DTR||output||Data Terminal Ready|
|6||6||DSR||input||Data Set Ready|
|7||4||RTS||output||Request to Send|
|8||5||CTS||input||Clear to Send|
You need the following parts to build this shutdown button with LEDs.
The above image shows the etched circuit board. I don't have an exact board layout for you because I prefer to do small circuits as free hand drawing directly on the board with etch resistant ink.
The final circuit with all parts is shown on the picture at the top of this article. You can carefully drill 3 holes into the front panel of your server. Two 3mm holes for the LEDs and one to screw in the push button. The whole circuit is very light and the screw of the push button will be enough to hold it.
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2001-01-27, generated by lfparser version 2.8