Public bug reported:

I am not sure to what extent this should be treated as a bug, perhaps
best to start with some discussion.

When a user sets a resolution in Unity Control Centre, that resolution
is remembered (in a file called $HOME/.config/monitors.xml) and unity-
settings-daemon always tries to set that resolution on that monitor.  In
general this is a good idea, but unity-settings-daemon uses EDID data to
distinguish monitors.  This breaks in virtual machines (tested in
VirtualBox, but I believe this affects other hypervisors too) which
simulate monitor hot-plug to get guest systems to adjust to the size of
the window on the host in which the virtual machine is being displayed.
The hypervisors generally do not provide EDID data, and u-s-d does not
realise that these are different monitors.  So either the monitor is
kept to a standard resolution or u-s-d flashes up a message, "Could not
apply the stored configuration for monitors", to complain if the
resolution selected no longer exists.

The simplest solution might be not to remember the resolution if no EDID
data is available.

See also https://answers.launchpad.net/unity-settings-
daemon/+question/284461

ProblemType: Bug
DistroRelease: Ubuntu 15.10
Package: unity-settings-daemon 15.04.1+15.10.20151029-0ubuntu1
ProcVersionSignature: Ubuntu 4.2.0-27.32-generic 4.2.8-ckt1
Uname: Linux 4.2.0-27-generic x86_64
ApportVersion: 2.19.1-0ubuntu5
Architecture: amd64
CurrentDesktop: Unity
Date: Tue Feb  9 15:23:59 2016
InstallationDate: Installed on 2015-11-16 (85 days ago)
InstallationMedia: Ubuntu 15.10 "Wily Werewolf" - Release amd64 (20151021)
SourcePackage: unity-settings-daemon
UpgradeStatus: No upgrade log present (probably fresh install)

** Affects: unity-settings-daemon (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: amd64 apport-bug wily

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https://bugs.launchpad.net/bugs/1543619

Title:
  unity-settings-daemon randr support has problems in virtual machines

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