hello
I am using ubuntu on android(with chroot)
I am trying to execute xev
(to change the volume button to CTRL)
but every time I trying to open up xev,
it says
unable to open the display ''
or
unable to open the display '127.0.0.1:0.0'
(when I change DISPLAY variable with export)

I can't find official error page on google
could somebody tell me how to solve this problem?
just giving me several possible reason
or
your little advice would be very helpful for me


Regards.
Taeyun.