Puting system to 'sleep'

[Matthew Garrett]

On Sat, 2005-01-08 at 19:03 +0100, Carsten wrote:

> Unfortunately at the moment there are three different approaches to
> enable linux using suspend modes. Only one of them, PMDisk, is enabled
> in the Ubuntu default kernel. This is the most reliable one but it will
> still be crashing many systems or make them suspend but never wake up
> again, so use with care!

PMDisk isn't enabled in the default Warty kernel. Hoary will ship with
swsusp enabled by default.

> Then again, often it just won't do anything at all. And there's no
> graphical UI I'd know about.
> To enable PMDisk open a root shell and enter
> echo -n "standby" > /sys/power/state

Uh, that's not PMDisk. Depending on whether you're on an APM or an ACPI
system, that'll trigger a fairly light suspend to RAM.

> There are two alternative sleep modes you can replace "standby" with:
> "mem" and "disk".
> Before the first try you absolutely should change to non-graphical
> single user mode, do a "sync" and have no files opened you still need.
> The problem usually is not getting the machine asleep but waking it up
> again. At desktop PCs it often works by pressing the power button,
> laptops vary very much.

"mem" is a much heavier suspend to ram than "standby" is. But they're
both more similar to each other than they are to "disk", which will
trigger PMDisk (on older kernels) and swsusp (on newer ones).

It's likely that Hoary will support suspend to RAM on most machines, but
it may not be enabled by default.
-- 
Matthew Garrett | mjg59 at srcf.ucam.org