Can't reboot from ssh command line

[Michael R Head]

On Sun, 2005-09-04 at 15:50 -0400, Stephen R Laniel wrote:
> On Sun, Sep 04, 2005 at 03:42:56PM -0400, Michael R Head wrote:
> > Right, but it might be possible to set up a start-up time in the
> > system's BIOS. For example, if you want the machine to start up at
> > 8:55AM, so it has 5 minutes to boot before you reach your desk at 9, you
> > should be able to configure that, though linux would have nothing in
> > particular to do with that.
> 
> That's possible, though it seems unlikely. The BIOS still
> needs power running through it in order to do anything, and
> with the machine off it won't have that power. Or is the
> BIOS still powered even when the machine is off? Obviously
> certain parts of the machine -- like the clock -- need to be
> running all the time; I'm not clear whether the BIOS is one
> of those components.

Since ATX emerged, the motherboard has had control over the power
supply. The power button is a soft-switch which asks the motherboard to
turn on the main power. As long as the computer is plugged in, the
motherboard actually gets a (small) current. 

See the ATX spec, section 4.1.3.2:
http://www.formfactors.org/FFDetail.asp?FFID=1&CatID=1

4.1.3.2 5VSB
     5VSB is a standby voltage that may be used to power circuits that require power input during the powered-
     down state of the power rails. This power may be used to operate circuits such as soft power control. It is
     recommended that the 5VSB line be capable of delivering 2 A. This current allows the implementation of
     features such as Wake on LAN technology in accordance with IAPC (see
     http://developer.intel.com/technology/iapc/index.htm for more information).


> 
> This reminds me, sorta, of the "magic ping." I've never used
> it, but I'm told that some machines can be brought out of
> *standby* -- not out of a full power-off state -- by an
> appropriately shaped IP packet.

This is wake-on-lan, and requires communication between the motherboard
and the ethernet chip. It can indeed remotely power up a machine that is
configured for it.

-- 
Michael R Head <burner at suppressingfire.org>
GPG: http://www.suppressingfire.org/~burner/gpg.key.txt (ID 23A02B1F)
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 189 bytes
Desc: This is a digitally signed message part
URL: <https://lists.ubuntu.com/archives/ubuntu-users/attachments/20050904/76591216/attachment.sig>