sysrq k(kill) always kill the Xorg under Desktop.
the best way will kill One program, chrome or vbox or java will better than kill Xorg.
or one more short-key will better
---
ApportVersion: 2.20.1-0ubuntu2.1
Architecture: amd64
AudioDevicesInUse:
USER PID ACCESS COMMAND
/dev/snd/controlC0: gshmu 24229 F.... pulseaudio
/dev/snd/controlC1: gshmu 24229 F.... pulseaudio
CurrentDesktop: Unity
DistroRelease: Ubuntu 16.04
EcryptfsInUse: Yes
InstallationDate: Installed on 2015-04-22 (579 days ago)
InstallationMedia: Ubuntu 14.04 LTS "Trusty Tahr" - Release amd64 (20140417)
MachineType: Dell Inc. OptiPlex 9020
Package: linux (not installed)
ProcFB: 0 inteldrmfb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.4.0-47-generic root=UUID=7b10211b-954c-44e1-b525-91b27505c8ad ro quiet splash vt.handoff=7
ProcVersionSignature: Ubuntu 4.4.0-47.68-generic 4.4.24
RelatedPackageVersions:
linux-restricted-modules-4.4.0-47-generic N/A
linux-backports-modules-4.4.0-47-generic N/A
linux-firmware 1.157.5
RfKill:
Tags: xenial
Uname: Linux 4.4.0-47-generic x86_64
UpgradeStatus: Upgraded to xenial on 2016-08-02 (111 days ago)
UserGroups: adm cdrom dip fuse libvirtd lpadmin plugdev sambashare sudo vboxusers
_MarkForUpload: True
dmi.bios.date: 01/08/2015
dmi.bios.vendor: Dell Inc.
dmi.bios.version: A10
dmi.board.name: 03CPWF
dmi.board.vendor: Dell Inc.
dmi.board.version: A00
dmi.chassis.type: 6
dmi.chassis.vendor: Dell Inc.
dmi.modalias: dmi:bvnDellInc.:bvrA10:bd01/08/2015:svnDellInc.:pnOptiPlex9020:pvr01:rvnDellInc.:rn03CPWF:rvrA00:cvnDellInc.:ct6:cvr:
dmi.product.name: OptiPlex 9020
dmi.product.version: 01
dmi.sys.vendor: Dell Inc.
This bug is missing log files that will aid in diagnosing the problem. From a terminal window please run:
apport-collect 1643474
and then change the status of the bug to 'Confirmed'.
If, due to the nature of the issue you have encountered, you are unable to run this command, please add a comment stating that fact and change the bug status to 'Confirmed'.
This change has been made by an automated script, maintained by the Ubuntu Kernel Team.