Probably you have an X-server running and there are some processes you are not aware of.
The ":0.0" is a way in X-Windows to specify where output of a program (a "X-client") should go. This is what the $DISPLAY-variable is for.
The generic form is
DISPLAY=<hostname>:<display-number>.<screen-number>
<hostname> is a normal hostname, specifying the hostname (or directly the IP-adress) of the host which should receive the output to display it.
<display> is the number of the display on this host. A display is one (or more, see below) screen(s), a mouse and a keyboard. In most cases this is 0 because hosts (like PCs) tend to have only one display, but back then hosts were big systems and had several displays attached to them so that many users could work simultaneously. For these hosts there had to be a way to specify which display was to be adressed.
<screen> is the number of the screen. If you are sitting in front of a PC with only one monitor this is always 0, but suppose you would have several monitors. In this case you would still have one "display", but this display would consist of several "screens". (If you are using one of these graphic cards which can use several monitors you might still have one screen which spans several monitors, but this is just a workaround for Windoze systems which couldn't adress several screens originally.) You number these screens (again starting at 0) and can so decide where the output should go. For instance, if you have 3 monitors "localhost:0.0" would adress your left monitor, "localhost:0.1" would adress the middle one and "localhost:0.2" the right one.
You can find further information about X-Windows at the X-Free86 website (
X-Free86 project).
Find the manual page describing the above here:
X(7) manual page
I hope this helps.
bakunin
