Does FBSD support 'software suspend' ?

[Nate Lawson]

Fabian Keil wrote:
> "Kevin Oberman" <oberman at es.net> wrote:
> 
> 
>>>           Does FBSD support 'software suspend' like linux does ?
>>>Also,from the archives i come to know that FBSD supports
>>>'suspend to disk'.What is the exact difference between the two ?
>>>or are they one and the same ?
>>
>>FreeBSD tries to support both. They are more technically referred to as S3 and 
>>S4 states but are more typically called "suspend to RAM" and "suspend to disk" 
>>respectively. The terms "suspend" and "hibernate" are also used.
> 
> 
> AFAIK "software suspend" does not equal to "suspend to RAM".
> 
> There are two different "suspend to disk" modes. One is "software suspend"
> the other "BIOS suspend". The second needs help by the BIOS and a special
> formated slice, the first doesn't.
> 
> FreeBSD supports "BIOS supend" if the hardware supports it,
> you can tell by checking hw.acpi.s4bios with sysctl.
> 

Correct.  FreeBSD supports S4BIOS but not S4OS (yet).  Most newer 
systems don't support S4BIOS so suspend-to-disk isn't supported in most 
systems.

We welcome anyone who wants to implement S4OS.

> GNU/Linux supports software suspend for S4 as well, ATM FreeBSD doesn't.

Linux supports S4OS a little but swsusp* is really an ACPI-independent 
feature where the OS writes everything to disk and then on a fresh 
bootup sees if it should read the frozen image.  It doesn't require ACPI 
support at all.

We welcome anyone who wants to implement this kind of hibernate support 
also since it overlaps a lot with the work to implement S4OS.

-- 
Nate