Energy Saving in the Statistical Laboratory

Quick Start

To save energy:

All Linux workstations turn themselves off if idle at 22:00 every evening
Office computers turn back on at 08:00 every morning unless you have requested otherwise
Public computers remain off until switched on manually

What you can do to help:

Switch off monitors when they are not in use
When switching off Windows computers, shut them down via the Start menu
When switching off Linux computers, use the ``safeshutdown'' command
When restarting Linux computers, use ``safereboot''
If your computer crashes or won't turn on, tell me (I won't notice until I have cause to turn it on myself)

If you can't connect to your favourite computer:

If you just want to check your email, use sirtommy instead
For more intensive work, ssh/putty into sirtommy and activate your machine with the ``wake'' command

Overview

Monitors and other computer peripherals such as speakers and office printers can be turned off whenever they are not in use, as can Windows computers (shutting them down via Windows is preferable to pressing the power switch).

Until recently, shutting down Linux computers was not encouraged, for two reasons. First, a remote user might be using the PC or running a job on it when it was shut down, and second, they might wish to log in while the computer was off and find themselves unable to do so. However, there are now solutions to these problems - the ``safeshutdown'' command will check whether a Statslab machine is idle before powering it down, and the ``wake'' command can be run on one Statslab machine to activate another one.

Therefore I have configured the Linux computers to shut themselves down at 22:00 every night if they are idle. At present machines in offices will turn themselves on automatically at 08:00 every morning unless the user has requested otherwise, but this may change. If you would like the automatic morning wakeup disabled for your machine then please tell me. (Of course this means that if something goes wrong with your machine I'll have no way of knowing.)

Shutting Down Linux Computers

The best way to shut down a computer on the Statslab network is to type ``safeshutdown'', a local command which will automatically check that the computer is idle before powering it off. Note that Linux will only let you shut a computer down when you are actually sitting at it, not when you are logged in remotely. ``safereboot'' is a similar command which will restart only idle computers, useful if your computer seems to have got into a mess.

Those of you who use Linux machines outside the Statslab may find it useful to know more about the checks which are automatically run by safeshutdown and safereboot. To see whether a computer is in use, type ``w'' into a terminal window. The output will look like this:

 10:30:57 up 14 days, 45 min,  3 users,  load average: 0.02, 0.10, 0.08
USER     TTY      FROM              LOGIN@   IDLE   JCPU   PCPU WHAT
eva      :0       -                08:59   ?xdm?  48:42   0.16s -/bin/tcsh -c /
eva      pts/2    :0.0             08:59    0.00s  0.07s  0.01s w
eva      pts/1    :0.0             08:59   21:47   0.54s  0.02s ssh ermyers@chi

The ``load average'' mentioned in the first line is a measure of how heavily loaded the computer is. (The three numbers are the load averages for the last 1, 5, and 15 minutes.) If any of these numbers is over 0.5, someone is probably running a long job on your computer, and it should be left on.

The remaining lines indicate who is logged onto the computer, where they are logged on from, when they logged on, and what they are doing. They contain a lot of information in a very small space, but for the purpose of determining whether the computer is in use, you need only look at the first column. If you see any login name other than your own, that person is using the computer, and it must be left on.

In the example above, the computer is unloaded and no-one but me is using it, so I could safely shut it down to save power. The easiest way to do this is to select ``Shut Down'' from the System menu. You can also type ``poweroff''.

Waking Up Linux Computers

With the new policy of turning off idle machines in effect, you may find that your favourite computer is switched off when you want to connect to it from home. It is a good idea to use the ``ping'' command to check before connecting. You can either do your work on an alternative computer, or connect to sirtommy and wake up your computer with the ``wake'' command e.g. ``wake martha''. The wake command works on any Statslab machine, but sirtommy is guaranteed to be up at all times because it is the Mathematica and NAG licence server.

If you have a recurring problem with ``your'' computer being down when you want to use it, there are several options. You can leave yourself logged in at all times so that it never shuts down automatically. You can ask me to turn on the 8:00 am wakeup, which may have been disabled at the request of the previous user of your office. Technically savvy users can run their own cron jobs on sirtommy to wake up their computer at a time which suits them.

If you want to wake up some computers in order to run a number-crunching job, then this list of Statslab computers and their ages may be of interest to you.