Isso provavelmente se deve a um problema de configuração incorreta ou a vários monitores. Como pode ser visto no xterm manpage ( man xterm ) você pode definir a exibição usando o -display flag:
-display display
This option specifies the X server to contact; see X(7).
Se você olhar em X(7) onde especifica a aparência ( man X ) você verá o que você precisa colocar após o sinalizador:
DISPLAY NAMES
From the user's perspective, every X server has a display name of the
form:
hostname:displaynumber.screennumber
This information is used by the application to determine how it should
connect to the server and which screen it should use by default (on
displays with multiple monitors):
hostname
The hostname specifies the name of the machine to which the
display is physically connected. If the hostname is not given,
the most efficient way of communicating to a server on the same
machine will be used.
displaynumber
The phrase "display" is usually used to refer to a collection
of monitors that share a common set of input devices (keyboard,
mouse, tablet, etc.). Most workstations tend to only have one
display. Larger, multi-user systems, however, frequently have
several displays so that more than one person can be doing
graphics work at once. To avoid confusion, each display on a
machine is assigned a display number (beginning at 0) when the
X server for that display is started. The display number must
always be given in a display name.
screennumber
Some displays share their input devices among two or more moni‐
tors. These may be configured as a single logical screen,
which allows windows to move across screens, or as individual
screens, each with their own set of windows. If configured
such that each monitor has its own set of windows, each screen
is assigned a screen number (beginning at 0) when the X server
for that display is started. If the screen number is not
given, screen 0 will be used.
On POSIX systems, the default display name is stored in your DISPLAY
environment variable. This variable is set automatically by the xterm
terminal emulator. However, when you log into another machine on a
network, you may need to set DISPLAY by hand to point to your display.
For example,
% setenv DISPLAY myws:0
$ DISPLAY=myws:0; export DISPLAY
The ssh program can be used to start an X program on a remote machine;
it automatically sets the DISPLAY variable correctly.
Finally, most X programs accept a command line option of -display dis‐
playname to temporarily override the contents of DISPLAY. This is most
commonly used to pop windows on another person's screen or as part of a
"remote shell" command to start an xterm pointing back to your display.
For example,
% xeyes -display joesws:0 -geometry 1000x1000+0+0
% rsh big xterm -display myws:0 -ls </dev/null &
X servers listen for connections on a variety of different communica‐
tions channels (network byte streams, shared memory, etc.). Since
there can be more than one way of contacting a given server, The host‐
name part of the display name is used to determine the type of channel
(also called a transport layer) to be used. X servers generally sup‐
port the following types of connections:
local
The hostname part of the display name should be the empty
string. For example: :0, :1, and :0.1. The most efficient
local transport will be chosen.
TCPIP
The hostname part of the display name should be the server
machine's hostname or IP address. Full Internet names, abbre‐
viated names, IPv4 addresses, and IPv6 addresses are all
allowed. For example: x.org:0, expo:0, [::1]:0,
198.112.45.11:0, bigmachine:1, and hydra:0.1.
Para obter o valor da sua exibição, você só poderá executar:
echo $DISPLAY