How do I do a COLD Reboot on FreeBSD?

Bart Silverstrim bsilver at
Mon Jan 31 12:29:40 PST 2005

On Jan 31, 2005, at 1:53 PM, Billy Newsom wrote:

> Jerry McAllister wrote:
>> Well, I guess I completely do not understand what you are asking.
>>> From anything I can get from what you write here, its behavior is
>> normal and expected.   What is the problem and what are you trying to 
>> fix or to get it to do?
>> A cold boot - which is what you ask about in your original post - is
>> a boot all the way up from a powered off machine as far as I know.
>> So, all I did was explain how to get what you asked for in the post.
> No, I said a cold reboot.  That's the term for a reboot which runs the 
> entire POST, counts memory, etc.  The screen looks identical to a cold 
> start or cold boot.  We all know what the warm reboot means -- that's 
> when many parts of the POST are skipped.  Windows uses a cold reboot, 
> for example, when you click "Restart" on the Shutdown menu.  FreeBSD 
> does a warm reboot using the reboot command.  The warm reboot may save 
> thirty to sixty seconds over the cold reboot.  A warm reboot typically 
> skips the memory check and does a cursory check of hard drive 
> parameters, etc. to save time.
> If you use a PC DOCTOR disk and tell it to reboot, it will do a cold 
> reboot.  When you flash your BIOS from DOS, it will usually do a cold 
> reboot when it exits.  When you save changes and reboot from the BIOS 
> setup screen, it will do a cold reboot.  Many other examples are 
> possible.
> What I tried to explain is that this PC crashes on the subsequent boot 
> if a warm reboot is performed by FreeBSD.  But if I could perform a 
> cold reboot every time, this would solve the issue.  A cold reboot is 
> not the act of "shutting the power off and turning it back on."  That 
> is called a power cycle and it is obviously manual.  A cold reboot is 
> done by a special software command.

I was always told a cold reboot comes from powering down the system; 
minimal power to the logic board and wiping any and all traces possible 
(short of unplugging it) of random crap in the capacitors and memory.  
Literally cold boot because usually it happened after powering it down 
and it would cool off until the user came back to work on their 
computer for awhile.

Warm boots basically just cycle the computer to restart the OS.  It's 
just restarting it, and power to the components has been maintained the 
whole time so as far as the computer hardware is concerned nothing 
really happened, just a chunk of memory access and the processor mode 
getting kicked around a bit.

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