Hi,
I'm interested in saving power on Linux desktops and I'd like to
compare notes with like-minded people.
I'm a system administrator in a University department with roughly a
thousand Linux desktops. Starting in a few months' time the
department is going to be responsible for its own electricity bills
and this is concentrating our minds wonderfully on ways we might make
our computers run more efficiently.
One way of doing this is obviously through the kernel improvements
championed on the Less Watts site, but we're hoping that we'll
basically get these improvements over the next few years more or less
for free as we upgrade to newer kernels with more power-saving
features - our freedom to upgrade to newer kernel versions between
annual OS upgrades is severely constrained. So, for the moment we're
looking mainly at making our desktops sleep when idle.
Currently the Linux desktops run 24 hours per day, 7 days per week.
The machines need to be on at some point during the night to do
automated maintenance, such as adding and removing software packages
- but we'd like to have them sleep for at least the rest of the night
if they're not in use, and maybe during other idle periods as well.
Has anybody else been looking at this? What experience have you
had? A lot of power-saving effort seems to go into laptops but
surprisingly little into desktops from what I've seen so far. Any
experience or tips would be really welcome!
You're also welcome to take a look at what I've found out, such as it
is.
Here's a basic summary of what I've discovered so far - starting from
pretty much no knowledge of this area:
* Suspend and Hibernate work pretty reliably on the distributions
we currently use (mostly FC6 and SL5).
* You can control them at several levels (e.g. Gnome or KDE,
command line utilities, /proc or /sys).
* A machine that's powered down can be made to respond to a Wake
On LAN signal but I couldn't get a suspended or hibernating machine
to do so.
* Wake Alarms are a far more hopeful way of getting machines to
wake up during the night: simply tell the machine just before
suspending or hibernating it precisely when you want it to wake up
again. This seems to work pretty well.
* Scripts in /etc/pm/hooks/ are run when a machine sleeps or
wakes up.
* The automounter we use, "amd", crashes when FC6 resumes, but is
happy on the SL5 machines.
* ACPI, pm-utils, acpid, DBus, HAL, gnome-power-manager,
TuxOnIce, swsusp, oh my...
The full saga of blind alleys, puzzlement and slow progress can be
trawled through at https://wiki.inf.ed.ac.uk/DICE/MPUPowerDiary and
https://duffus.inf.ed.ac.uk/blog/chris/tag/power-management/ - feel
free to take a look.
-- Chris Cooke.
Computing Officer, School of Informatics, University of Edinburgh.
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