how to force a hard reboot remotely

Gary Kline kline at
Sun Jul 17 04:26:55 UTC 2011

On Sat, Jul 16, 2011 at 10:39:06PM -0500, Ryan Coleman wrote:
> Date: Sat, 16 Jul 2011 22:39:06 -0500
> From: Ryan Coleman <editor at>
> Subject: Re: how to force a hard reboot remotely
> To: Bill Tillman <btillman99 at>
> Cc: freebsd-questions at
> X-Mailer: Apple Mail (2.1084)
> When bottom replying, please clear the header and signature - thanks.
> You can set up a BIOS boot time, if you can get onsite... that would allow you to power it down at, say, 11:59PM and have it power back on at Midnight.
> Or a UPS that's controlled by another machine. Or the magic packet WOL option... but those require another machine. Maybe a switch or router than can send WOL packets would be a possibility?
> --
> Ryan

	I had something like this in late 1995.  Remotely 
	"shutdown -h [time]"  got my box powered down, then a 
	remote timer cycled the power.  Problems were: that the 
	timer was hard to set exacrly.  [There may have ben two
	timers; it was a bear of a problem.  ]


> On Jul 16, 2011, at 10:31 PM, Bill Tillman wrote:
> > 
> > WOW! That's a tall order. A reboot from remote is simple, but a cold boot....I 
> > don't think that's possible unless you have some kind of Wake-On-Lan capable NIC 
> > which could detect a connection attempt while the machine is off. I can't say 
> > that for sure because what you've got to remember is that with a cold boot, the 
> > machine will no longer remember what OS it was running until it reboots. My 
> > advice would be to get to the console if you absolutely have to cold boot it. Or 
> > call someone nearby the console and have the actually turn the machine off, wait 
> > the obligatory 30 seconds and then restart it. Someone else may have a better 
> > idea.
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 Gary Kline  kline at  Public Service Unix
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