Enable hibernation

[Steve Langasek]

On Fri, Jan 03, 2014 at 05:08:28PM -0500, Phillip Susi wrote:
> On 1/3/2014 4:50 PM, Steve Langasek wrote:
> > The hibernate menu option was disabled because it was exposed in
> > many cases where hibernate would not work reliably.  Indeed, I was
> > recently trying to

> According to whom? Is there any record of this testing?  My experience
> ( and many others ) is that hibernate is more reliable than suspend
> since it doesn't rely on often buggy bios.  If there is evidence that
> it is terribly unreliable, I'd like to see it.

As far back as the Maverick (i.e., 10.10) release notes[1], we prominently
documented the fact that the hibernate option was not reliable:

  Hibernation may be unavailable with automatic partitioning. The default
  partitioning recipe in the installer will in some cases allocate a swap
  partition that is smaller than the physical memory in the system.  This
  will prevent the use of hibernation (suspend-to-disk) because the system
  image will not fit in the swap partition.  If you intend to use
  hibernation with your system, you should ensure that the swap partition's
  size is at least as large as the system's physical RAM.  (345126)
  https://bugs.launchpad.net/ubuntu/+source/partman-auto/+bug/345126

This was subsequently discussed at UDS, where the decision was taken to drop
the option from the menu, because despite Colin fixing the recipe, there
were still other issues with the implementation.  Specifically, I remember
two main technical problems:

 - if a newer kernel package has been installed (which happens frequently),
   resume from hibernation will fail.
 - if there is insufficient memory, hibernation will fail.

There was also the design issue:

 - the difference between suspend and hibernate is opaque to the average
   user; the user should not have to guess between them.

It would be nice if we had a ready index for such decisions at past UDSes,
but unfortunately we don't.


> > make pm-hibernate work for me on the commandline in trusty (because
> > my machine seems to be in its death throes and suspend no longer
> > works reliably for me), and found that, even though I have a 6GB
> > swap partition and 4GB of RAM, I am consistently unable to
> > hibernate here (I think kernel changes wrt dm-crypt may be to
> > blame).

> If there's a bug with hibernation and dm-crypt, it should be addressed.

If you were to fix these bugs, I'm sure no one would be unhappy with that.
It doesn't sound like you're volunteering to fix them, though, but instead
insisting that some unspecified other should be required to do the work to
make this reliable.

The Tech Board can require that technical changes be done in a certain way,
but it cannot make resources appear from thin air.  As long as these bugs
remain unaddressed, I think it's a reasonable technical decision to suppress
the hibernate option by default.

(Personally I would like nothing more than to see the dm-crypt issues sorted
out, since if I'm right this is the cause of extreme memory pressure on my
machine under normal usage too, and not just something that breaks
hibernation.  But wanting the bug fixed and having it fixed are, of course,
two different things.)

> > I don't think we should have a menu option exposed by default which
> > will fail to work for a large number of users (in most cases, after
> > first churning the disk for a minute or two).  And at the time this
> > decision was made, there were not resources to make this menu
> > option work *reliably* in Ubuntu.

> How many is "large"?  I've never seen many people complaining about it
> either on askubuntu, or the ubuntuforums, or filing bug reports, so I
> find this claim hard to believe.  What is it specifically that
> prevents it from working reliably, and in what cases?

Well, aside from the fact that askubuntu didn't become a significant support
platform until exactly the time the hibernate option disappeared from the
menu, that doesn't sound like a very scientific approach to the question.
Certainly, <http://askubuntu.com/search?q=hibernate> lists a large number of
results, the very first of which is a complaint that pm-hibernate is failing
after upgrade to 12.04.

As far as I can see, what's needed here is for someone to do the work to
expose the option in the UI only when we can know that hibernate will
succeed.  I think we should also still have design team input regarding
which of suspend and hibernate should be exposed in the UI by default.

-- 
Steve Langasek                   Give me a lever long enough and a Free OS
Debian Developer                   to set it on, and I can move the world.
Ubuntu Developer                                    http://www.debian.org/
slangasek at ubuntu.com                                     vorlon at debian.org

[1] https://wiki.ubuntu.com/MaverickMeerkat/ReleaseNotes
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