Comment 11 for bug 883618

This xset problem is caused by update-manager calling /usr/bin/xdg-screensaver which in turns calls xset.

DistUpgrade/DistUpgradeQuirks.py in update-manager invokes 'xdg-screensaver reset' repeatedly and xdg-screensaver makes a number of calls to xprop and xset. An example of a problematic call to xset by xdg-screensaver:

xset -q | grep 'DPMS is Enabled' > /dev/null 2> /dev/null

If DISPLAY is not set (as will be the case on a VT), 'xset -q' will write the following text to stderr:

xset: unable to open display ""

xdg-screensaver should probably be calling xset like this:

xset -q 2>/dev/null | grep 'DPMS is Enabled' > /dev/null 2> /dev/null

However, the easiest and quickest fix is to have update-manager invoke xdg-screensaver with stdout+stderr redirected to /dev/null.

What is not clear at this stage is what is causing the failing calls to xprop since all the calls made by xdg-screensaver appear to be safe.