Can't reboot from ssh command line

[Bernard Peek]

In message <20050904195028.GA14276 at TheloniousMonk.laniels.org>, Stephen 
R Laniel <steve at laniels.org> writes
>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.

The clock is running and can signal the power supply to switch on. The 
problem is that every machine I've seen just allows one time to be set, 
and it will wake at the same time each day. You could configure the 
machine to switch off again if unused for a while, so a work machine 
would still wake at 08:55 at weekends, but would sleep again an hour 
later.

>
>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.

It's called Wake On LAN (WoL) and it only works if you have the right 
hardware and BIOS. The "Magic packet" needs to be sent to the network 
card's MAC address. There are Windows and Linux utilities that can send 
out magic packets.

Recent machines don't normally power right down, part of the system 
stays awake and can kick the PSU into life by generating the appropriate 
interrupt. That can be done from a network card, the internal clock or a 
serial port. So you can have a machine powered down but it wake up to 
answer the phone when the modem gets a call.




-- 
Bernard Peek
London, UK. DBA, Manager, Trainer & Author.