[Beowulf] Strange "resume" statements generated for GRUB2

[Skylar Thompson]

On 06/09/2013 11:37 AM, Mikhail Kuzminsky wrote:
> I have swap in sda1 and "/" in sda2 partitions of HDD. At installation
> of OpenSUSE 12.3 (where YaST2 is used) on my cluster node I found
> erroneous, by my opinion, boot loader (GRUB2) settings.
> 
> YaST2 proposed (at installation) to use
> ... resume=/dev/disk/by-id/ata-WDC-... -part1 splash=silent ...
> 
> in configuration of GRUB2. This parameters are transmitted (at linux
> loading) by GRUB2 to linux kernel. GRUB2 itself, according my
> installation settings, was installed to MBR. I changed (at installation
> stage) -part1 to -part2, but after that YaST2 restored it back to -
> part1 value !
> And after installation OpenSuSE boots successfully !
> I found (in installed OpenSuSE) 2 GRUB2 configuration files w/erroneous
> -part1 setting.
> 
> I found possible interpretation of this behaviour in /var/log/messages.
> I found in this file the strings:
> [Kernel] PM: Checking hibernation image partition
> /dev/disk/by-id/ata-WDC_...-part1
> 
> [Kernel] PM: Hibernation Image partition 8:1 present
> [Kernel] PM: Looking for hibernation image.
> {Kernel] PM: Image not found (code -22)
> [Kernel] PM: Hibernation Image partitions not present or could not be loaded
> 
> What does it means ? The hibernation image is writing to swap partition
> ?  But I beleive that hibernation is really suppressed in my Linux
> (cpufreq kernel modules are not loaded) , and my BIOS settings do not
> allow any changes of CPU frequency. BTW, my swap partition is small (4
> GB, but RAM size is  8 GB).
> 
> Which GRUB2/resume settings are really right and why they are right ?

Hibernation isn't strictly suspension - it's writing all allocated,
non-file-backed portions of memory to the paging/swap space. When the
system comes out of hibernation, it boots normally and then looks for a
hibernation image in the paging space. If it finds one, it loads that
back into system memory rather than proceeding with a regular boot. This
is in contract to system suspension, which depends on hardware support
to place CPU, memory, and other system devices into a low power state,
and wait for a signal to power things back up, bypassing the boot process.

I'm not a SuSE expert so I'm not sure what YaST is doing, but I imagine
you have to make grub changes via YaST rather than editing the grub
configs directly.

Skylar