On Wed, Sep 28, 2011 at 9:46 AM, Alan Cox <alan@lxorguk.ukuu.org.uk> wrote:

sshd sets it when you do an ssh -X/-Y. If it isn't getting set then
either ssh isn't seeing suitable environment variables (eg ssh'ing into a
box and forgetting which box you were on when you do the ssh -Y), or it
can be blocked in the sshd config.

Alan

Thanks for the reply, Alan.  Great to see you jump in like that.

How/when is X supposed to be started ? Part of the boot process, right ?   Does anything shut it down, like a "timeout" on the login screen ?

Thanks