system doesnt power off after shutdown

[James Wilkinson]

Aroon Pahwa wrote:
> when i choose to shut down ubuntu, everything shuts down fine but when
> all is done it just sits there and never actually powers off.  it does
> say power down so i just have to switch off the computer manually.
> 
> im assuming my acpi settings are not correct?  im running hoary final
> on a p3 850 and some random gateway motherboard that im assuming is
> running the intel bx440 chipset.
> 
> anyone know what i need to change, what i should change it to, and how
> i should change it?

Power down is the responsibility of either APM or ACPI. Your computer's
BIOS is supposed to supply appropriate data which the operating system
can use to manage the system's power (e.g. hibernate support). APM is
the older standard [1]; ACPI is newer, a lot more complicated, and does
a lot more. [2]

But on a BX desktop, about all you would need either for is automatic
power off.

ACPI and APM are mutually incompatible: only one can be used at any one
time. Both have had a tendency to be buggy: in the past, "quality
assurance" meant "will it boot Windows?".

On 2.6 kernels with both options built, ACPI will be used in preference
to APM unless the system's BIOS is earlier than a certain date. BIOSes
earlier than this are too likely to be buggy. (I *think* Ubuntu has this
turned off: my install's an AMD 64 one, so I can't check).

The Linux default is to disable ACPI on BIOSes earlier than 2001: right
around when your system was built.

If ACPI is disabled, APM will be used instead.

In any case, you can check what you're running at the moment by looking
at /var/log/dmesg (which is a text file) and searching for mentions of
ACPI. If it gets thirty or more mentions, it's being used. If it's only
mentioned once or twice, it will probably be next to a message telling
you that it's been disabled.

You can force ACPI on or off by *carefully* editing the
/boot/grub/menu.lst file. There'll be a lot of comments (beginning with
#) and default options. Then there'll be a number of "stanzas", each
beginning with a line marked "title".

You might want to make a copy of the default stanza and play with that:
that way you've got the original there for use in an emergency. Each
stanza corresponds to one line in the bootup grub menu.

At the end of the kernel line, add "acpi=off" or "acpi=force" to turn
ACPI off (and APM on) or make sure ACPI is on. For example,

kernel          /boot/vmlinuz root=/dev/hdb6 ro console=tty0 quiet splash

would be

kernel          /boot/vmlinuz root=/dev/hdb6 ro console=tty0 quiet splash acpi=off

Hope this helps,

James.

[1] And incompatible with multiple processors...
[2] For example, it provides data on how the system is configured. A few
newer systems need ACPI working to even boot: I think most of the
Itanium systems do.

-- 
E-mail address: james | "Ok, so your monitor is not working, the screen is
@westexe.demon.co.uk  | blank, and no matter what you do it stays blank? Do
                      | you see that button on the bottom right hand side of
                      | the screen? Press it. . . ."