[CentOS] Power Fail Protection Update

Wed Aug 16 18:07:14 UTC 2017
Chris Murphy <lists at colorremedies.com>

On Wed, Aug 16, 2017 at 8:49 AM, Chris Olson <chris_e_olson at yahoo.com> wrote:
> Many thanks to those that responded to my original posting with
> information about Network UPS Tools and commercial UPS products.
> In our planning a path forward to implement UPS-based power fail
> protection, we have come across what appears to be an issue with
> the state of the CentOS 6 machines being UPS protected.  Most of
> these machines are desktop/deskside machines that are likely to
> be idle during non-work hours.  It is also likely that they will
> be hibernating or in a power save mode.
> In the power save mode, these machines do not respond to keyboard
> or mouse activity.  They also do not respond to network traffic
> such as a ping from other systems on the network.  The method we
> use to wake them up is a quick push on the power button when the
> hibernation state is indicated by the button's yellow LED display.
> This state of hibernation leaves us wondering if these systems will
> be able to respond to network messages sent by the UPS.  We have not
> yet made it all the way through the NUT and UPS documentation.
> The hibernation answer may very well be therein, but we have not
> found it so far.  Any help or direction regarding the hibernation
> issue as it relates to UPS power fail protection will be appreciated.

Suspend to RAM and suspend to disk both sync filesystems before the
system suspends, so what should be true is the file system is
consistent. The log might be dirty, but this would be replayed at next
boot if there's a power failure.

The only thing that would be lost is any unsaved work. The old school
answer is, save your files before you sleep the computer; i.e. the
burden is on the user.

My position is, this is a solved problem on mobile, where apps take
responsibility for saving state including user data. Some do this
locally, some sync it to the cloud. So far I'm not seeing this become
much of a thing on the desktop, other than macOS where it's fairly
standard at this point. Libreoffice by default saves autorecovery
information every 10 minutes, for example.

Chris Murphy