diff -up VirtualBox-5.2.6/src/VBox/Additions/x11/Installer/98vboxadd-xclient~ VirtualBox-5.2.6/src/VBox/Additions/x11/Installer/98vboxadd-xclient

--- VirtualBox-5.2.6/src/VBox/Additions/x11/Installer/98vboxadd-xclient~	2018-01-15 15:49:57.000000000 +0100

+++ VirtualBox-5.2.6/src/VBox/Additions/x11/Installer/98vboxadd-xclient	2018-02-07 12:13:51.578170786 +0100

@@ -21,13 +21,9 @@ for i in $HOME/.vboxclient-*.pid; do

     test -w $i || rm -f $i

 done

-if ! test -c /dev/vboxguest 2>/dev/null; then

-   # Do not start if the kernel module is not present.

-   notify-send "VBoxClient: the VirtualBox kernel service is not running.  Exiting."

-elif test -z "${SSH_CONNECTION}"; then

-   # This script can also be triggered by a connection over SSH, which is not

-   # what we had in mind, so we do not start VBoxClient in that case.  We do

-   # not use "exit" here as this script is "source"d, not executed.

+# Do not start if the kernel module is not present; or if this script is

+# triggered by a connection over SSH.

+if [ -c /dev/vboxguest -a -z "${SSH_CONNECTION}" ]; then

   /usr/bin/VBoxClient --clipboard

   /usr/bin/VBoxClient --checkhostversion

   /usr/bin/VBoxClient --display