Powersaving

Turning machines off

We are trying to reduce the electricity we use, so our plan is for office computers which are not doing anything useful to turn themselves off.

The current proposal is that at 6pm and also 5 minutes after anyone logs out of the console, a script will run which turns the machine off if no user processes are running. User processes are local and remote logins and batch computing jobs.

This means that machines will not turn themselves off when anyone is logged in (although exceptions could be made) and if your office mate logs out you can comfortably log in without the machine turning off on you.

You could turn your office computer yourself (with either the button on the front with the blue light or from one of the on-screen menus - even when logged off!) but this risks interrupting any long-running calculations or people who are using the machine remotely. Just log off and let the machine turn itself off if it can do so safely.

Turning machines on

Our desktop computers are intended to be available for members of the department to use for long or large calculations. It may help such number crunchers to know that they can turn our machines on remotely from any of our machines with the command:
  wake <machinename>
One way would be to use ssh (or putty) to log into ssh.dpmms.cam.ac.uk and run wake from there.

Turning machines on automatically

If you often work in college and log into your office machine at 9 every weekday morning you could set a cron job to wake your machine up; the cron line would be:

0 9 * * 1,2,3,4,5 wake machinename

You would probably want both tern and pheasant to run this command (in case one of them was unavailable). If you are not familiar with the command crontab -e the easiest way to set this up would to run the command on both machines:

vcron -regular wake machinename

and select the time the command should run. This does require a graphical session - you may have to investigate crontab -e if you only have a putty connection.

Screens

Our LCD screens use very little power (too little for my meter to measure) when the computer is sending a powersaving screen-blank signal. You are however free to turn the screen off yourself if you wish.

If the powersaving screen-blank kicks in too slowly (or to quickly) you can change the timings with the dpms option to the xset command.